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Ecological communities can be stable over multiple generations, or rapidly shift into structurally and functionally different configurations. In kelp forest ecosystems, overgrazing by sea urchins can abruptly shift forests into alternative states that are void of macroalgae and primarily dominated by actively grazing sea urchins. Beginning in 2014, a sea urchin outbreak along the central coast of California resulted in a patchy mosaic of remnant forests interspersed with sea urchin barrens. In this study, we used a 14-year subtidal monitoring dataset of invertebrates, algae, and fishes to explore changes in community structure associated with the loss of forests. We found that the spatial mosaic of barrens and forests resulted in a region-wide shift in community structure. However, the magnitude of kelp forest loss and taxonomic-level consequences were spatially heterogeneous. Taxonomic diversity declined across the region, but there were no declines in richness for any group, suggesting compositional redistribution. Baseline ecological and environmental conditions, and sea urchin behaviour, explained the persistence of forests through multiple stressors. These results indicate that spatial heterogeneity in preexisting ecological and environmental conditions can explain patterns of community change.

Sea urchins, ecologically important marine species, host a complex gut microbiota that plays a significant role in their digestion, nutrient acquisition, and overall health. The gut microbes, along with endogenous enzymes, facilitate the breakdown of macroalgae and other food sources. Environmental factors, including temperature, salinity, and habitat type, can greatly influence the microbial communities within sea urchins. Dietary variations can also lead to shifts in the abundance and composition of intestinal bacteria, highlighting the strong connection between diet and gut microbiota. The sea urchin's unique anatomy and digestive system adaptations contribute to their ability to process and absorb nutrients efficiently, supporting their varied diets. Gut microbes not only participate in the decomposition of complex carbohydrates, but also in detoxifying compounds and mitigating the impacts of inhospitable environments. Further research is needed to fully understand the intricate relationships between sea urchin species, their habitats, diets, and gut microbiota composition. A deeper understanding of these interactions may inform sustainable management and aquaculture strategies, ensure the long‐term viability of economically valuable sea urchin species, and provide insights into their ecological roles and adaptability to changing environments. [ABSTRACT FROM AUTHOR]

The die‐off of the long‐spined sea urchin Diadema antillarum in the 1980s highlighted its crucial role as a primary grazer in tropical western Atlantic coral reefs. However, natural recovery has been slow, exacerbated by a new die‐off in 2022. Interest in actively restoring D. antillarum populations has grown with the emergence of culture and rearing techniques. Restocking reefs with laboratory‐reared urchins shows potential for enhancing coral reef resilience by reducing algal cover and promoting coral settlement, but success rates vary. Predation and migration contribute to low retention rates, with distinguishing between them is challenging. In this study near Saba, Caribbean Netherlands, we released 200 laboratory‐reared D. antillarum on a reef and monitored for D. antillarum retention and potential D. antillarum predator presence and interaction for 35 days. Only 40% of the urchins were still present on the reef after day one. The Spanish hogfish Bodianus rufus was identified as the primary daytime predator, responsible for nine direct predation events. No nighttime predation was observed, but interaction with a batwing coral crab Carpilius corallinus was noted. These insights can help optimize future restocking attempts and emphasize the importance of assessing predator presence beforehand. Reefs with high abundances of predators such as Spanish hogfish should be avoided for D antillarum restocking. In addition, before being released, lab‐reared animals should be given time to acclimate to conditions in the wild by being placed in protected in situ cages. Here, they could also grow to larger sizes that are less vulnerable to predation. [ABSTRACT FROM AUTHOR]

It is essential to understand the spatial distribution of a target species for effective stock management, particularly in the case of less mobile rock-dwelling species such as sea urchins. However, sea urchins exhibit an aggregated distribution within fishing grounds, thereby necessitating diving surveys at multiple sites to elucidate their spatial distribution at a fine scale. In Mikuni, Sakai City, Fukui Prefecture, Japan, female divers are well-acquainted with the underwater landscape and can determine the sea urchin catch per fishing ground. They also conduct voluntary fishery management for the sea urchin. Therefore, we enlisted female divers to report the sea urchin Hemicentrotus pulcherrimus catch during the 2020–2022 period and subsequently visualized the spatial distribution of these catches and estimated initial abundance using the Leslie method according to the fishing ground. The catch per unit effort did not decrease although the cumulative catch increased in many fishing grounds. This was because divers sensibly perceived the status of sea urchin stocks at each fishing ground through the dive fishery and they voluntarily controlled their fishing efforts to prevent stock depletion. Our results highlight that the catch data are often used for stock estimation but are influenced by fishermen's management of the fishery. [ABSTRACT FROM AUTHOR]

Gametogenesis and the accumulation of nutrients such as proteins progress in sea urchin gonads during their growth. In vertebrate species, these physiological mechanisms are regulated by nuclear receptors. Although it has been estimated that there are several dozen nuclear receptor homologs in the genome of the purple sea urchin Strongylocentrotus purpuratus their functions and which ones are expressed in the gonads remain unclear. Here, we investigated the expression of nuclear receptor genes in early gametogenesis and the dynamics of their expression during germ cell formation in the northern sea urchin Mesocentrotus nudus. First, we identified the vasa sequence in M. nudus, and quantitative PCR of vasa and histological analysis revealed that germline cells were undergoing proliferation and differentiation in the growing gonads. During this period, 23 nuclear receptor genes were expressed in the male and female gonads. The expression levels of five nuclear receptor genes (eip78c, trβ, bar, rxrγ, and ftz-f1β) were found to be increased during gonadal growth in both sexes, suggesting that these nuclear receptors exert certain functions during the growth period of the gonads. Our results provide the first comprehensive experimental data on nuclear receptors for a species of sea urchin. [ABSTRACT FROM AUTHOR]

Our knowledge of the assembly and dynamics of the cytokinetic contractile ring (CR) in animal cells remains incomplete. We have previously used super-resolution light microscopy and platinum replica electron microscopy to elucidate the ultrastructural organization of the CR in first division sea urchin embryos. To date, our studies indicate that the CR initiates as an equatorial band of clusters containing myosin II, actin, septin and anillin, which then congress over time into patches which coalesce into a linear array characteristic of mature CRs. In the present study, we applied super-resolution interferometric photoactivated localization microscopy to confirm the existence of septin filament-like structures in the developing CR, demonstrate the close associations between septin2, anillin, and myosin II in the CR, as well as to show that septin2 appears consistently submembranous, whereas anillin is more widely distributed in the early CR. We also provide evidence that the major actin cross-linking protein α-actinin only associates with the linearized, late-stage CR and not with the early CR clusters, providing further support to the idea that α-actinin associates with actomyosin structures under tension and can serve as a counterbalance. In addition, we show that inhibition of actomyosin contraction does not stop the assembly of the early CR clusters but does arrest the progression of these structures to the aligned arrays required for functional cytokinesis. Taken together our results reinforce and extend our model for a cluster to patch to linear structural progression of the CR in sea urchin embryos and highlight the evolutionary relationships with cytokinesis in fission yeast. [ABSTRACT FROM AUTHOR]

Sea urchins are basal deuterostomes that share key molecular components of innate immunity with vertebrates. They are a powerful model for the study of innate immune system evolution and function, especially during early development. Here we characterize the morphology and associated molecular markers of larval immune cell types in a newly developed model sea urchin, Lytechinus pictus. We then challenge larvae through infection with an established pathogenic Vibrio and characterize phenotypic and molecular responses. We contrast these to the previously described immune responses of the purple sea urchin Strongylocentrotus purpuratus. The results revealed shared cellular morphologies and homologs of known pigment cell immunocyte markers (PKS, srcr142) but a striking absence of subsets of perforin‐like macpf genes in blastocoelar cell immunocytes. We also identified novel patterning of cells expressing a scavenger receptor cysteine rich (SRCR) gene in the coelomic pouches of the larva (the embryonic stem cell niche). The SRCR signal becomes further enriched in both pouches in response to bacterial infection. Collectively, these results provide a foundation for the study of immune responses in L. pictus. The characterization of the larval immune system of this rapidly developing and genetically enabled sea urchin species will facilitate more sophisticated studies of innate immunity and the crosstalk between the immune system and development. [ABSTRACT FROM AUTHOR]

Our knowledge of the assembly and dynamics of the cytokinetic contractile ring (CR) in animal cells remains incomplete. We have previously used superresolution light microscopy and platinum replica electron microscopy to elucidate the ultrastructural organization of the CR in first division sea urchin embryos. To date, our studies indicate that the CR initiates as an equatorial band of clusters containing myosin II, actin, septin and anillin, which then congress over time into patches which coalesce into a linear array characteristic of mature CRs. In the present study, we applied super-resolution interferometric photoactivated localization microscopy to confirm the existence of septin filament-like structures in the developing CR, demonstrate the close associations between septin2, anillin, and myosin II in the CR, as well as to show that septin2 appears consistently submembranous, whereas anillin is more widely distributed in the early CR. We also provide evidence that the major actin cross-linking protein a-actinin only associates with the linearized, late-stage CR and not with the early CR clusters, providing further support to the idea that a-actinin associates with actomyosin structures under tension and can serve as a counterbalance. In addition, we show that inhibition of actomyosin contraction does not stop the assembly of the early CR clusters but does arrest the progression of these structures to the aligned arrays required for functional cytokinesis. Taken together our results reinforce and extend our model for a cluster to patch to linear structural progression of the CR in sea urchin embryos and highlight the evolutionary relationships with cytokinesis in fission yeast. [ABSTRACT FROM AUTHOR]

The development of the sea urchin larval body plan is well understood from extensive studies of embryonic patterning. However, fewer studies have investigated the late larval stages during which the unique pentaradial adult body plan develops. Previous work on late larval development highlights major tissue changes leading up to metamorphosis, but the location of specific cell types during juvenile development is less understood. Here, we improve on technical limitations by applying highly sensitive hybridization chain reaction fluorescent in situ hybridization (HCR-FISH) to the fast-developing and transparent sea urchin Lytechinus pictus , with a focus on skeletogenic cells. First, we show that HCR-FISH can be used in L. pictus to precisely localize skeletogenic cells in the rudiment. In doing so, we provide a detailed staging scheme for the appearance of skeletogenic cells around the rudiment prior to and during biomineralization and show that many skeletogenic cells unassociated with larval rods localize outside of the rudiment prior to localizing inside. Second, we show that downstream biomineralization genes have similar expression patterns during larval and juvenile skeletogenesis, suggesting some conservation of skeletogenic mechanisms during development between stages. Third, we find co-expression of blastocoelar and skeletogenic cell markers around juvenile skeleton located outside of the rudiment, which is consistent with data showing that cells from the non-skeletogenic mesoderm embryonic lineage contribute to the juvenile skeletogenic cell lineage. This work sets the foundation for subsequent studies of other cell types in the late larva of L. pictus to better understand juvenile body plan development, patterning, and evolution. [Display omitted] • Indirect development in sea urchins has made juvenile development challenging to study. • Juvenile sea urchin development can be better understood by applying HCR-FISH. • Skeletogenic gene expression patterns are similar during larval and juvenile development. • Blastocoelar genes are sometimes expressed in presumptive juvenile skeletogenic cells. [ABSTRACT FROM AUTHOR]

The Persian Gulf is a semi-closed inland sea with specific ecological conditions, and the level of oil pollution in it exceeds the global average acceptable for the marine environment. Echinoderms, due to their benthic nature, are more exposed to sediment pollution. This study was conducted in the intertidal zones of Bushehr province, including the shores of Shaghab, Owli, Shirino, Nay-Band, the T-pier and the Northern Khark Island, to determine the level of contamination in sediments and the tissue of the sea urchin Echinometra mathaei. Sampling was carried out in two seasons, winter and summer (2014-2015). In the laboratory, the samples were analyzed for the type and concentration of polycyclic aromatic hydrocarbons (PAHs) using chromatography and GC-MS. The highest concentration of PAHs in the sediments at the T pier in Khark was found to be naphthalene (913.7ng/g dry weight) in the winter, while the highest concentration of PAHs in the tissue was measured as phenanthrene (371.5ng/g dry weight) in the summer. No significant difference was observed between the levels of PAHs in sediments and tissues (P>0.05). The trend of PAH accumulation in sediments and tissues was increasing. The level of PAHs in sediments across all study areas (3059- 441ng/g) was higher than the global standards set for sediments (197µg/kg), indicating greater pollution in the examined areas. A comparison of pollution accumulation in the tissues of the sea urchin with other aquatic species revealed higher PAH levels in the tissues of benthic species. This finding is due to the habitat and feeding type of these organisms, highlighting the importance of this species and the need for environmental toxicological studies on it. [ABSTRACT FROM AUTHOR]

The effect of a fraction of phlorethol (CcPh), one of the polyphenolic compounds isolated from the brown alga Costaria costata (Turn.) Saund (Laminariales), on gametes and embryogenesis of the sea urchin Strongylocentrotus intermedius (A. Agassiz, 1864) was studied. Using a model of developing sea urchin embryos, it was shown that phlorethol at concentrations of ≤700 μg/mL did not exert a cytotoxic effect on early developmental stages (from the zygote to the 16-celled stage blastomere). The embryotoxic effect of phlorethol that caused the death of 50% of the embryos was expressed in a concentration (I) range of 50 < I ≤ 100 μg/mL only after 24 h of incubation, in the blastula stage. When exposed to concentrations greater than 100 μg/mL, embryos that survived to the blastula stage did not develop further and died after 36 h of incubation. Under the effect of phlorethol, the fertilizing capacity of sea urchin spermatozoa and oocytes decreased. The concentration of phlorethol that inhibited fertilization by 50% (IC50) when acting on sperm was 1.28 ± 0.38 μg/mL and when acting on oocytes was 3.83 ± 0.82 μg/mL. Thus, phlorethol reduces the fertilizing capacity of sea urchin gametes at concentrations much lower than embryotoxic concentrations and can potentially find practical application as part of new contraceptive drugs for mammals and humans. [ABSTRACT FROM AUTHOR]

Bacterial assemblages associated with sea urchin are critical to their physiology and ecology within marine ecosystems. In this study, we characterized the bacterial communities in wild sea urchin Anthocidaris crassispina captured in Daya Bay, South China Sea. A total of 363 amplicon sequence variants belonging to nine phyla and 141 genera were classified from intestine, body surface, and surrounding seawater samples. Proteobacteria, Firmicutes, and Bacteroidetes were the dominant bacteria phyla found in this study. A network analysis of bacterial interspecies interactions revealed varying complexity, stability, connectivity, and relationship patterns across the samples, with the most intricate network observed in the surrounding seawater. Metagenomic predictions highlighted the distinct bacterial metabolic pathways, with significant differences between intestine and seawater samples. Notably, pathways associated with polysaccharide degradation, including chitin derivatives, starch, and CoM biosynthesis, were markedly abundant, underscoring the gut microbiota's key role in digesting algae. In addition, other metabolic pathways in intestine samples were linked to immune response regulation of sea urchins. Overall, this study provides a comprehensive overview of the bacterial community structure and potential functional roles in A. crassispina. [ABSTRACT FROM AUTHOR]

Climate change is causing increased coastal freshening in Antarctica, leading to reduced salinity. For Antarctica's endemic echinoderms, adapted to the stable polar environment, the impact of rapid reductions in coastal salinity on physiology and behaviour is currently unknown. Six common Antarctic echinoderms (the sea urchin Sterechinus neumayeri; the sea star Odontaster validus; the brittle star Ophionotus victoriae; and three sea cucumbers Cucumaria georgiana, Echinopsolus charcoti and Heterocucumis steineni), were directly transferred from ambient salinity (34.5‰) to a range of salinity dilutions (29–9‰) for 24 h. All species showed reduced activity and the establishment of a temporary osmotic gradient between coelomic fluid and external seawater. Most species exhibited a depression in oxygen consumption across tolerated salinities; however, at very low salinities that later resulted in mortality, oxygen consumption increased to levels comparable to those at ambient. Low salinity tolerance varied substantially between species, with O. victoriae being the least tolerant (24 h LC50 (lethal for 50% of animals) = 19.9‰) while E. charcoti and C. georgiana demonstrated the greatest tolerance (24 h LC50 = 11.5‰). These findings demonstrate the species-specific response of Antarctica's endemic echinoderms to short-term hypoosmotic salinity events, providing valuable insight into this phylum's ability to respond to an underreported impact of climate change. [ABSTRACT FROM AUTHOR]

Background: Echinometra mathaei (family Echinometridae), is one of the sea urchins widely distributed on the Egyptian coasts in the Red Sea. This organism contains edible and non-edible parts. The present study was carried out to analyze and identify the metabolites present in the non-edible parts (Aristotle's lantern and viscera) using LC/MS. Also, the cytotoxic activity on Vero cell line and antiviral activity against herpes simplex virus type 1 were evaluated using MTT colorimetric assay. Results: Chemical profiling of the crude extracts of Aristotle's lantern and viscera using LC/MS indicated the presence of 51 and 59 compounds, respectively. The main metabolites present in both non-edible parts were phospholipids, amino acids, peptides, fatty acids and glycerol derivatives. However, the characteristic difference was the presence of carotenoid pigments only in viscera. The crude extract of Aristotle's lantern and viscera showed no cytotoxic activity on Vero cell line and significant antiviral activity against herpes simplex virus with an IC50 value equal to 115.48 ± 1.20 and 122.4 ± 0.50 µg/mL, respectively. Conclusions: In the present study, the crude extracts of the non-edible parts of E. mathaei were analyzed using LC.MS.MS.QTOF and indicated the existence of 110 chemical compounds, with significant antiviral activity against HSV-1 and no cytotoxic activity. The diversity of the identified compounds with two main categories of compounds, phospholipids and peptides, may contribute to the antiviral activity of Aristotle's lantern and viscera. Additionally, this research focused on clarification of nutritive, pharmaceutical and economic values of these parts. As future prospects, further studies are required to isolate the metabolites and assess the detailed mechanism of antiviral activity via in vitro, in vivo and in silico studies. [ABSTRACT FROM AUTHOR]

miR-31 is a highly conserved microRNA that plays crucial roles in cell proliferation, migration and differentiation. We discovered that miR-31 and some of its validated targets are enriched on the mitotic spindle of the dividing sea urchin embryo and mammalian cells. Using the sea urchin embryo, we found that miR-31 inhibition led to developmental delay correlated with increased cytoskeletal and chromosomal defects. We identified miR-31 to directly suppress several actin remodeling transcripts, including β-actin, Gelsolin, Rab35 and Fascin. De novo translation of Fascin occurs at the mitotic spindle of sea urchin embryos and mammalian cells. Importantly, miR-31 inhibition leads to a significant a increase of newly translated Fascin at the spindle of dividing sea urchin embryos. Forced ectopic localization of Fascin transcripts to the cell membrane and translation led to significant developmental and chromosomal segregation defects, highlighting the importance of the regulation of local translation by miR-31 at the mitotic spindle to ensure proper cell division. Furthermore, miR-31-mediated post-transcriptional regulation at the mitotic spindle may be an evolutionarily conserved regulatory paradigm of mitosis. [ABSTRACT FROM AUTHOR]

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Kelp forests have deteriorated globally due to anthropogenic stressors. There is an urgent need to extend baselines, to understand the processes that underlie the persistence and recovery of kelp forests, and to distinguish the normal range of ecosystem variability from more extreme changes. Using a mixed-method, historical ecology approach, we integrate archival data, oral histories, and contemporary ecological data to examine the dynamics of kelp forests over a multi-decadal to multi-century time-period in central California. We focus on sea otters, sunflower seastars, sea urchins, kelp cover, kelp species dynamics, and climate. From 1826 to 2020, kelp was highly variable. There were seven periods of low kelp cover and two periods of exceptionally low kelp cover (1897–1899; 2014–2016) following El Niño-Southern Oscillations (ENSOs). Exceptionally low kelp cover did not occur when two predators—seastars and sea otters—were both present. In all cases, kelp recovered following times of extremely low cover, with a lag, which was extended by the duration of warm water anomalies (ENSO Recovery Lag). Kelp remained low for approximately 2 years following 80% of ENSOs. The greatest kelp decline (12-fold) was in Santa Cruz (northern Monterey Bay). Herbivore populations (sea urchins) were highly variable over the past century and exhibited short- and long-term changes in abundance. Sunflower seastars were present in low, stable abundances prior to seastar wasting disease (1938–2013, mean density = 0.02/m2) when they declined by 97.5%. Insights from this reconstruction indicate that kelp recovery following extended warm water anomalies exhibits a lag and occurs over multiple years. [ABSTRACT FROM AUTHOR]

The sea urchin Tripneustes gratilla holds substantial ecological and economic importance in tropical marine ecosystems. To better understand the population structure and genetic diversity of T. gratilla, here we developed a suite of 29 polymorphic microsatellite makers based on high-throughput sequencing. The range of alleles characterized by these primers varied from 6 to 19, with an average number of 12.31. The observed and expected heterozygosities ranged from 0.250 to 1.000 and from 0.808 to 0.955, respectively. All the polymorphism information content values of the 29 loci were above 0.5, suggestive of highly informative. Demonstrating adherence to Hardy–Weinberg equilibrium, these 29 primer pairs present robust candidates for conducting population genetics and phylogeographic analyses in T. gratilla, which may provide valuable information for sustainable management and conservation efforts of this urchin. [ABSTRACT FROM AUTHOR]

We have previously shown that Golgi stacks and recycling endosomes (REs) exist as Golgi/RE units in sea urchin embryos. In this study, we showed that Golgi/RE units were scattered throughout the cytoplasm at early developmental stages but gathered to form a “Golgi ring” surrounding the centric REs at the blastula stage. This change in the cell-wide arrangement of Golgi/RE units coincided with a dramatic change in microtubule organization from a randomly oriented cortical pattern to radial arrays under the apical plasma membrane. A single gigantic Golgi apparatus surrounding centric RE is clearly associated with the center of the radial microtubule arrays. Furthermore, we found that in some animal species belonging to different clades, Golgi stacks lack lateral connections but are likely centralized by microtubule motors. These results suggest that Golgi centralization depends on the organization of the microtubule array in addition to the lateral linking between Golgi stacks. Key words: Golgi stack, recycling endosome, Golgi-ribbon, microtubule, cilium, sea urchin, ascidian

Abstract Background Echinometra mathaei (family Echinometridae), is one of the sea urchins widely distributed on the Egyptian coasts in the Red Sea. This organism contains edible and non-edible parts. The present study was carried out to analyze and identify the metabolites present in the non-edible parts (Aristotle's lantern and viscera) using LC/MS. Also, the cytotoxic activity on Vero cell line and antiviral activity against herpes simplex virus type 1 were evaluated using MTT colorimetric assay. Results Chemical profiling of the crude extracts of Aristotle's lantern and viscera using LC/MS indicated the presence of 51 and 59 compounds, respectively. The main metabolites present in both non-edible parts were phospholipids, amino acids, peptides, fatty acids and glycerol derivatives. However, the characteristic difference was the presence of carotenoid pigments only in viscera. The crude extract of Aristotle's lantern and viscera showed no cytotoxic activity on Vero cell line and significant antiviral activity against herpes simplex virus with an IC50 value equal to 115.48 ± 1.20 and 122.4 ± 0.50 µg/mL, respectively. Conclusions In the present study, the crude extracts of the non-edible parts of E. mathaei were analyzed using LC.MS.MS.QTOF and indicated the existence of 110 chemical compounds, with significant antiviral activity against HSV-1 and no cytotoxic activity. The diversity of the identified compounds with two main categories of compounds, phospholipids and peptides, may contribute to the antiviral activity of Aristotle's lantern and viscera. Additionally, this research focused on clarification of nutritive, pharmaceutical and economic values of these parts. As future prospects, further studies are required to isolate the metabolites and assess the detailed mechanism of antiviral activity via in vitro, in vivo and in silico studies.

Growing evidence suggests that metabolic regulation directly influences cellular function and development and thus may be more dynamic than previously expected. In vivo and in real-time analysis of metabolite activities during development is crucial to test this idea directly. In this study, we employ two metabolic biosensors to track the dynamics of pyruvate and oxidative phosphorylation (Oxphos) during the early embryogenesis of the sea urchin. A pyruvate sensor, PyronicSF, shows the signal enrichment on the mitotic apparatus, which is consistent with the localization patterns of the corresponding enzyme, pyruvate kinase (PKM). The addition of pyruvate increases the PyronicSF signal, while PKM knockdown decreases its signal, responding to the pyruvate level in the cell. Similarly, a ratio-metric sensor, Grx-roGFP, that reads the redox potential of the cell responds to DTT and H 2 O 2 , the known reducer and inducer of Oxphos. These observations suggest that these metabolic biosensors faithfully reflect the metabolic status in the cell during embryogenesis. The time-lapse imaging of these biosensors suggests that pyruvate and Oxphos levels change both spatially and temporarily during embryonic development. Pyruvate level is increased first in micromeres compared to other blastomeres at the 16-cell stage and remains high in ectoderm while decreasing in endomesoderm during gastrulation. In contrast, the Oxphos signal first decreases in micromeres at the 16-cell stage, while it increases in the endomesoderm during gastrulation, showing the opposite trend of the pyruvate signal. These results suggest that metabolic regulation is indeed both temporally and spatially dynamic during embryogenesis, and these biosensors are a valuable tool to monitor metabolic activities in real-time in developing embryos. • PKM and pyruvate localize on the spindle and in the nucleus during early embryogenesis of the sea urchin. • Pyruvate is increased in micromeres, while Oxidative phosphorylation is decreased in micromeres. • Pyruvate and Oxidative phosphorylation sensors show an opposite trend of expression dynamics during embryogenesis. • Metabolic biosensors are valuable tools for analyzing in vivo metabolic regulation in developing embryos. [ABSTRACT FROM AUTHOR]

Dicer substrate interfering RNAs (DsiRNAs) destroy targeted transcripts using the RNA-Induced Silencing Complex (RISC) through a process called RNA interference (RNAi). This process is ubiquitous among eukaryotes. Here we report the utility of DsiRNA in embryos of the sea urchin Lytechinus variegatus (Lv). Specific knockdowns phenocopy known morpholino and inhibitor knockdowns, and DsiRNA offers a useful alternative to morpholinos. Methods are described for the design of specific DsiRNAs that lead to destruction of targeted mRNA. DsiRNAs directed against pks1 , an enzyme necessary for pigment production, show how successful DsiRNA perturbations are monitored by RNA in situ analysis and by qPCR to determine relative destruction of targeted mRNA. DsiRNA-based knockdowns phenocopy morpholino- and drug-based inhibition of nodal and lefty. Other knockdowns demonstrate that the RISC operates early in development as well as on genes that are first transcribed hours after gastrulation is completed. Thus, DsiRNAs effectively mediate destruction of targeted mRNA in the sea urchin embryo. The approach offers significant advantages over other widely used methods in the urchin in terms of cost, and ease of procurement, and offers sizeable experimental advantages in terms of ease of handling, injection, and knockdown validation. • DsiRNA provides an RNAi approach for perturbation of sea urchin embryos. • A dilution series of DsiRNA oligos reveals properties of the Nodal gradient in establishing the Dorsal-Ventral axis. [ABSTRACT FROM AUTHOR]

Drafting gene regulatory networks (GRNs) requires embryological knowledge pertaining to the cell type families, information on the regulatory genes, causal data from gene knockdown experiments and validations of the identified interactions by cis-regulatory analysis. We use multi-omics involving next-generation sequencing to obtain the necessary information for drafting the Strongylocentrotus purpuratus (Sp) posterior gut GRN. Here, we present an update to the GRN using: (1) a single-cell RNA-sequencing-derived cell atlas highlighting the 2 day-post-fertilization (dpf) sea urchin gastrula cell type families, as well as the genes expressed at the single-cell level; (2) a set of putative cis-regulatory modules and transcription factor-binding sites obtained from chromatin accessibility ATAC-seq data; and (3) interactions directionality obtained from differential bulk RNA sequencing following knockdown of the transcription factor Sp-Pdx1, a key regulator of gut patterning in sea urchins. Combining these datasets, we draft the GRN for the hindgut Sp-Pdx1-positive cells in the 2 dpf gastrula embryo. Overall, our data suggest the complex connectivity of the posterior gut GRN and increase the resolution of gene regulatory cascades operating within it. [ABSTRACT FROM AUTHOR]

Alterations in seawater chemistry posed by acidification may lead to immunological and antioxidant defence impairment in sea urchins, with differences among local populations. Here, we analyzed the effects of reduced pH on Paracentrotus lividus, with a multibiomarker approach, and the possible intraspecific variations in sea urchin responses. Two groups of animals with different ecological histories (i.e., the pattern of environmental characteristics and pressures experienced throughout the organism's lifetime) were maintained at ambient pH and pH reduced of 0.4 units for 8 months. Changes in gonadosomatic index (GSI), immunological, and oxidative stress biomarkers were assessed in coelomic fluid, gonads, and digestive tract. Animals maintained at reduced pH showed limited impact of seawater acidification compared to the ambient pH condition. However, sea urchins from the two sites were differently influenced by the seawater pH (as shown by multivariate analyses). GSI and immunological and antioxidant status were differentially modulated between the two sexes, with generally higher values in females, but differences between sexes in relation to the pH of exposure were limited. Overall, our findings highlight that the impact of environmental stressors may differ in sea urchins from different locations. This has implications for the maintenance of P. lividus wild populations under future global change scenarios. [ABSTRACT FROM AUTHOR]

Introduction: In recent decades, Caribbean coral reefs have lost many vital marine species due to diseases. The well-documented mass mortality event of the long-spined black sea urchin Diadema antillarum in the early 1980s stands out among these collapses. This die-off killed over 90% of D. antillarum changing the reefscape from coral to algal-dominated. Nearly 40 years later, D. antillarum populations have yet to recover. In early 2022, a new mortality event of D. antillarum was reported along the Caribbean, including Puerto Rico. Methods: This study identifies the gut microbiota changes associated with the D. antillarum during this mortality event. It contrasts them with the bacterial composition of gut samples from healthy individuals collected in 2019 by using 16S rRNA sequencing analyses. Results: Notably, the die-off group's core microbiome resembled bacteria commonly found in the human skin and gut, suggesting potential anthropogenic contamination and wastewater pollution as contributing factors to the 2022 dysbiosis. The animals collected in 2022, especially those with signs of disease, lacked keystone taxa normally found in Diadema including Photobacterium and Propionigenium. Discussion: The association between human microbes and disease stages in the long-spined urchin D. antillarum, especially in relation to anthropogenic contamination, highlights a complex interplay between environmental stressors and marine health. While these microbes might not be the direct cause of death in this species of sea urchins, their presence and proliferation can indicate underlying issues, such as immune depletion due to pollution, habitat destruction, or climate change, that ultimately compromise the health of these marine organisms. [ABSTRACT FROM AUTHOR]

It is crucial to understand the role of temperature in rearing sea urchin larvae for large-scale production of sea urchin seeds. The development of purple sea urchins, Heliocidaris crassispina, such as fertilization, hatching, embryonic development, larval growth, ingestion, metabolism, and metamorphosis, was investigated at four temperatures: 20, 24, 28, and 32 °C. In the four temperatures, fertilization and hatching of sea urchins first increased with temperature and then decreased. The optimal condition was found at a temperature of 28 °C, where the fertilization and hatching rates exceeded 90%, and embryonic development was highly synchronized. This condition did not differ from the results observed at a temperature of 24 °C (P > 0.05). The fertilization and hatching rates were lower at 20 °C and 32 °C, among which 32 °C had the fastest embryo development but the second highest mortality. In contrast, 20 °C had the slowest embryo development and the most increased mortality. The optimal growth temperature for larvae is 28 °C, at which their growth and development rate are the fastest. However, at 24 °C, it is the second highest. At 20 °C, the growth rate is the lowest, with sluggish physiological responses and the lowest digestion and metabolism capacity. The metamorphosis rate did not differ between 28 and 32 °C (P < 0.05), with 50.0% and 61.1%, respectively, while remaining below 4% at 20 °C. This indicates that temperature significantly impacts the early development of Heliocidaris crassispina sea urchins, whose larvae may be sensitive to low temperatures but have higher temperature tolerance. [ABSTRACT FROM AUTHOR]

Basket height and stocking density are crucial and related factors for successful commercial sea urchin aquaculture, but these factors have not been definitively determined for production of Tripneustes gratilla. This study investigated the effects of varying basket heights (deep 30 cm vs. shallow 15 cm) and stocking densities (4, 6 and 8 kg.m−2 or 13, 19 and 24% coverage of available basket surface area) on aquacultural production of T. gratilla. Contrary to previous suggestions, reduced consumption was identified as the cause of decreased production in deeper baskets. Consumption was significantly higher in shallow baskets than deep baskets for both the fresh seaweed, Ulva lacinulata, (W = 38, p = 0.026) and formulated feed (W = 76.5, p = 0.007). Consequently, baskets of approximately 15 cm deep are recommended to enhance production of T. gratilla and possibly other urchin species. Two subsequent trials assessed production of T. gratilla at different stocking densities. Trial 1 aimed to maximize urchin size over a three-month grow-out period using fresh U. lacinulata, while trial 2 focused on enhancing gonad production over two months using formulated feed. Although greater stocking density significantly reduced the specific growth rates of individual urchin mass in both trials (p < 0.044), there was no significant impact on mortality, net production or gonad size and quality. The variations in growth rates were attributed to spine loss resulting from negative behavioural interactions (F2, 9 = 9.551; p = 0.005). Based on the objectives of both grow-out and gonad-enhancement phases, we recommend a stocking density of approximately 20% coverage. [ABSTRACT FROM AUTHOR]

FoxO is a member of the evolutionary conserved family of transcription factors containing a Forkhead box, involved in many signaling pathways of physiological and pathological processes. In mammals, mutations or dysfunctions of the FoxO gene have been implicated in diverse diseases. FoxO homologs have been found in some invertebrates, including echinoderms. We have isolated the FoxO cDNA from the sea urchin Paracentrotus lividus (Pl-foxo) and characterized the corresponding gene and mRNA. In silico studies showed that secondary and tertiary structures of Pl-foxo protein corresponded to the vertebrate FoxO3 isoform, with highly conserved regions, especially in the DNA-binding domain. A phylogenetic analysis compared the Pl-foxo deduced protein with proteins from different animal species and confirmed its evolutionary conservation between vertebrates and invertebrates. The increased expression of Pl-foxo mRNA following the inhibition of the PI3K signaling pathway paralleled the upregulation of Pl-foxo target genes involved in apoptosis or cell-cycle arrest events (BI-1, Bax, MnSod). In silico studies comparing molecular data from sea urchins and other organisms predicted a network of Pl-foxo protein–protein interactions, as well as identified potential miRNAs involved in Pl-foxo gene regulation. Our data may provide new perspectives on the knowledge of the signaling pathways underlying sea urchin development. [ABSTRACT FROM AUTHOR]

Background: Sea urchins have contributed greatly to knowledge of fertilization, embryogenesis, and cell biology. However, until now, they have not been genetic model organisms because of their long generation times and lack of tools for husbandry and gene manipulation. We recently established the sea urchin Lytechinus pictus, as a multigenerational model Echinoderm, because of its relatively short generation time of 4–6 months and ease of laboratory culture. To take full advantage of this new multigenerational species, methods are needed to biobank and share genetically modified L. pictus sperm. Results: Here, we describe a method, based on sperm ion physiology that maintains L. pictus and Strongylocentrotus purpuratus sperm fertilizable for at least 5–10 weeks when stored at 0°C. We also describe a new method to cryopreserve sperm of both species. Sperm of both species can be frozen and thawed at least twice and still give rise to larvae that undergo metamorphosis. Conclusions: The simple methods we describe work well for both species, achieving >90% embryo development and producing larvae that undergo metamorphosis to juvenile adults. We hope that these methods will be useful to others working on marine invertebrate sperm. Key Findings: Sperm can maintain fertilizing capacity ex vivo for 5‐10 weeks when stored at 0oC.When freezing in liquid nitrogen no stepwise addition of cryoprotectant, or stepwise drop in temperature are required.A standard fertilization assay is presented to score cleavage stage sea urchin embryos produced by cryopreserved sperm.Sperm frozen and thawed more than once can produce larvae. [ABSTRACT FROM AUTHOR]

The black sea urchin (Arbacia lixula) is a keystone species inhabiting the coastal shallow waters of the Mediterranean Sea, which is a key driver of littoral communities' structure. Here, we present the first genome assembly and annotation of this species, standing as the first Arbacioida genome, including both nuclear and mitochondrial genomes. To obtain a chromosome-level assembly, we used a combination of PacBio high fidelity (HiFi) reads and chromatin capture reads (Omni-C). In addition, we generated a high-quality nuclear annotation of both coding and non-coding genes, by using published RNA-Seq data from several individuals of A. lixula and gene models from closely related species. The nuclear genome assembly has a total span of 607.91 Mb, being consistent with its experimentally estimated genome size. The assembly contains 22 chromosome-scale scaffolds (96.52% of the total length), which coincides with its known karyotype. A total of 72,767 transcripts were predicted from the nuclear genome, 24,171 coding, and 48,596 non-coding that included lncRNA, snoRNA, and tRNAs. The circularized mitochondrial genome had 15,740 bp comprising 13 protein-coding genes, 2 rRNA, and 22 tRNA. This reference genome will enhance ongoing A. lixula studies and benefit the wider sea urchin scientific community. [ABSTRACT FROM AUTHOR]

To the best of our knowledge, this study is the first to track and demonstrate the mortality event in Diadema setosum (Leske, 1778) along the Egyptian Red Sea coasts. The diadematid is a group of echinoid echinodermates that play an important ecological role in marine ecosystems. However, the current global mass mortality events in Diadema setosum have the potential to significantly change the fundamental structure of the ecosystem. This report was based on the 2023-summer observations of a D. setosum die-off during an ecological investigation in the northern Red Sea, Egypt. To determine the entirety of the event, a group from the Red Sea protectorates carried out an extensive survey simultaneously. The current survey covered the coastal regions of the Elba protectorate in the south, the Wadi El Gemal protected area in the middle, and Hurghada in the north. A diverse population of D. setosum was found dead on the bottom during both snorkeling and scuba diving. Representative photographs were taken at each explored site. Several features were noticed in the dead D. setosum, including a frail body, sand-covered body parts, spines distributed on the bottom, and inactive tube feet. The current findings, therefore, recommend crucially the performance of regular monitoring for the status of D. setosum. In addition, biological and ecological investigations are needed as soon as possible to interpret the causative and potential factors responsible for D. setosum loss. [ABSTRACT FROM AUTHOR]

Evechinus chloroticus (commonly known as kina) is a sea urchin species endemic to New Zealand. Its roe is a culinary delicacy to the indigenous Māori and a globally exported food product. Echinochrome A (Ech A) is a bioactive compound isolated from the waste product of kina shells and spines; however, the molecular mechanisms of Ech A bioactivity are not well understood, partly due to Ech A never being studied using unbiased genome‐wide analysis. To explore the high‐value pharmaceutical potential of kina food waste, we obtained unbiased functional genomic and proteomic profiles of yeast cells treated with Echinochrome A. Abundance was measured for 4100 proteins every 30 min for four hours using fluorescent microscopy, resulting in the identification of 92 proteins with significant alterations in protein abundance caused by Ech A treatment that were over‐represented with specific changes in DNA replication, repair and RNA binding after 30 min, followed by specific changes in the metabolism of metal ions (specifically iron and copper) from 60–240 min. Further analysis indicated that Ech A chelated iron, and that iron supplementation negated the growth inhibition caused by Ech A. Via a growth‐based genome‐wide analysis of 4800 gene deletion strains, 20 gene deletion strains were sensitive to Ech A in an iron‐dependent manner. These genes were over‐represented in the cellular response to oxidative stress, suggesting that Ech A suppressed growth inhibition caused by oxidative stress. Unexpectedly, genes integral to cardiolipin and inositol phosphate biosynthesis were required for Ech A bioactivity. Overall, these results identify genes, proteins, and cellular processes mediating the bioactivity of Ech A. Moreover, we demonstrate unbiased genomic and proteomic methodology that will be useful for characterizing bioactive compounds in food and food waste. [ABSTRACT FROM AUTHOR]

Simple Summary: Ocean warming has led to shifts in species distributions. The sea urchin Mesocentrotus nudus is commercially harvested in northern Japan. Although limited scientific reports on the presence of this species in Hokkaido are available from Cape Soya to Cape Erimo along the coast of the Sea of Japan, statistical data from catches indicate that it has extended its range to the Sea of Okhotsk and Pacific Ocean. In 2021, harmful algal blooms (HABs) occurred along the Pacific coast of Hokkaido, and massive die-offs of marine organisms, including M. nudus, were reported. This study aimed to redefine the presence of M. nudus in the Pacific Ocean off Hokkaido after the HABs. Field surveys were conducted, and M. nudus was confirmed in Akkeshi, the site farthest from Cape Soya among the areas where irregular catches of M. nudus were recorded in eastern Hokkaido, in 2023. All sea urchins were >6 years of age, indicating that they survived the HABs. The size and developmental stages of the ovaries and testes of collected individuals suggest the reproductive cycle of M. nudus in Akkeshi would synchronize with that of the specimens off Wakkanai, Cape Soya. Warming trends may lead to population increases in the future. Scientific reports on the distribution of Mesocentrotus nudus in Hokkaido are limited from Cape Soya to Cape Erimo along the coast of the Sea of Japan; however, fishery statistics show that its distribution has extended to the Sea of Okhotsk and Pacific Ocean off Hokkaido. In 2021, large-scale harmful algal blooms (HABs) occurred in the Pacific Ocean off eastern Hokkaido, resulting in the massive die-off of marine organisms, including M. nudus. This study aimed to redefine the distribution of M. nudus in the Pacific Ocean off eastern Hokkaido after the HABs. Field surveys were conducted in July, August, and December 2023 in Akkeshi, the site farthest from Cape Soya among the areas where irregular catches of M. nudus have been recorded in eastern Hokkaido, and the distribution of this species was confirmed in August and December. All sea urchins collected were >6 years of age, indicating that they survived the HABs. High gonad indices and spermatozoa-filled gonads were observed in the sea urchins collected in December, suggesting that the reproductive cycle of M. nudus in Akkeshi may be close to that observed in specimens off Wakkanai, Cape Soya. Warming trends may cause population increases in the future. [ABSTRACT FROM AUTHOR]

In this work, optical–structural and morphological behavior when Nd is incorporated into ZnO is studied. ZnO and Nd-doped ZnO (ZnO-Nd) films were deposited at 900 °C on Silicon n-type substrates (100) by using the Hot Filament Chemical Vapor Deposition (HFCVD) technique. For this, pellets were made by from powders of ZnO(s) and a mixture of ZnO(s):Nd(OH)3(s). The weight percent of the mixture ZnO:Nd(OH)3 in the pellet is 1:3. The gaseous precursor generation was carried out by chemical decomposition of the pellets using atomic hydrogen which was produced by a tungsten filament at 2000 °C. For the ZnO film, diffraction planes (100), (002), (101), (102), (110), and (103) were found by XRD. For the ZnO-Nd film, its planes are displaced, indicating the incorporation of Nd into the ZnO. EDS was used to confirm the Nd in the ZnO-Nd film with an atomic concentration (at%) of Nd = 10.79. An improvement in photoluminescence is observed for the ZnO-Nd film; this improvement is attributed to an increase in oxygen vacancies due to the presence of Nd. The important thing about this study is that by the HFCVD method, ZnO-Nd films can be obtained easily and with very short times; in addition, some oxide compounds can be obtained individually as initial precursors, which reduces the cost compared to other techniques. Something interesting is that the incorporation of Nd into ZnO by this method has not yet been studied, and depending on the method used, the PL of ZnO with Nd can increase or decrease, and by the HFCVD method the PL of the ZnO film, when Nd is incorporated, increases more than 15 times compared to the ZnO film. [ABSTRACT FROM AUTHOR]

Sea urchins produced by aquaculture could enhance declining wild populations and provide a sufficient roe product to satisfy increasing market demand. This study reports a method for large-scale rearing of the edible tropical sea urchin Salmacis sphaeroides, from induction of larval metamorphosis and settlement, to juvenile rearing and grow-out. Larvae were reared in 500-L hatchery tanks, on a diet of the microalga Chaetoceros muelleri at concentrations ranging from 2500 to 24,000 cells mL−1, with daily water renewal of one-third to two-thirds of the volume depending on their developmental stage. The larvae breeding protocol proved suitable for this species, and competent larvae occurred at 12 days post-fertilization. To induce metamorphosis, we tested exposure to potassium chloride (KCl) at different concentrations (0, 25, 50, 100, 200, and 400 mmol L−1) and for different durations (5, 10, and 20 min). Exposure to 200 mmol L−1 KCl for 5 min resulted in the highest proportion of metamorphosed individuals (41.67 ± 2.89 %). Using this method, the densities of juveniles attaching to settlement plates (232.50 ± 41.23 ind. per plate; settlement percentage ca. 3.88 ± 0.69 %) were approximately twice as high as those of the controls (105.75 ± 15.52 ind. per plate; settlement percentage ca. 1.76 ± 0.26 %). Next, two batches of juveniles were grown out in sea cages. In the first batch (deployed for ca. 4 months), the absolute growth rate of the test diameter (AGRD) was 12.79 ± 0.98 mm month−1 from May to September; in the second batch (deployed for 6 months), the AGRD was 5.68 ± 0.90 mm month−1 from October to May of the following year. Survival of the juvenile S. sphaeroides in the sea cages was high (86.56 %–100 %). Finally, the S. sphaeroides cultivated in the second batch were harvested (at a mean test diameter of 71.24 ± 1.45 mm, and wet weight of 101.24 ± 1.91 g) on May 28 of the second year; all animals had matured and could be successfully utilized as broodstock. The fatty acid composition of the gonads was then compared between cultivated and wild-collected adult S. sphaeroides. The proportion of polyunsaturated fatty acids in the cultivated sea urchins (16.59 ± 0.67 %) exceeded that in wild-collected individuals (13.13 ± 0.42 %). From these experiments we conclude that S. sphaeroides is a sea urchin species with excellent potential for aquaculture; the present methods and data will provide helpful information for their mass production in South China.

In early embryonic development, the cross-regulation of transcription factors and signaling pathways are critical in mediating developmental and physiological processes. Additionally, many studies have shown the importance of posttranscriptional regulation of signaling and network components mediated by microRNAs (miRNAs); however, how miRNAs are transcriptionally regulated is poorly understood. miRNAs are critical fine-tuners of many biological processes and their dysregulation leads to a variety of diseases and developmental defects. Previously, we have shown that miRNAs are dynamically expressed throughout sea urchin development, suggesting that miRNAs are likely to be under transcriptional regulation. Here, we used pharmacological inhibitors, genetic constructs, and loss-of-function reagents to assess the impact of key signaling pathways (Wnt, Nodal, MAPK, Sonic Hedgehog, Delta/Notch, VEGF, and BMP) and transcription factors (Alx1, Ets1/2, and Tbr) on the transcript levels of the evolutionarily conserved miR-1, miR-31, miR-92 and miR-124; the invertebrate-specific miR-71; and the echinoderm-specific miR-2002, miR-2007, and miR-2012. We also used computational methods to identify potential transcription factor binding sites of these miRNAs. Lists of binding motifs for transcription factors (TFs) were acquired from the MEME-Suite Motif Database and used as inputs for the algorithm FIMO (Find Individual Motif Occurrences), which detects short nucleotide motifs within larger sequences. Based on experimental data on miRNA expression in conjunction with bioinformatic predictions, we propose that the transcription factors Tbr, Alx1, and Ets1 regulate SpmiR-1, SpmiR-31, and SpmiR-71, respectively. We additionally observed significant effects on miRNA levels as a result of perturbations to Wnt, Nodal, MAPK, and Sonic Hedgehog signaling pathways, while no significant change on miRNA levels were observed with perturbations to Delta/Notch, VEGF, or BMP signaling pathways. Overall, this study provides insights into the transcriptional regulation of miRNAs by signaling pathways and transcription factors and contribute to our overall understanding of the genetic regulation of developmental processes. [ABSTRACT FROM AUTHOR]

Many animals have pigments when they themselves cannot see colour. Perhaps those pigments enable the animal to avoid predators, or to attract mates. Maybe even those pigmented surfaces are hosts for microbes, even when the microbes do not see colour. Do some pigments then serve as a chemical signal for a good or bad microbial substrate? Maybe pigments attract or repel various microbe types? Echinoderms serve as an important model to test the mechanisms of pigment-based microbial interactions. Echinoderms are marine benthic organisms, ranging from intertidal habitats to depths of thousands of metres and are exposed to large varieties of microbes. They are also highly pigmented, with a diverse variety of colours between and even within species. Here we focus on one type of pigment (naphthoquinones) made by polyketide synthase, modified by flavin-dependent monoxygenases, and on one type of function, microbial interaction. Recent successes in targeted gene inactivation by CRISPR/Cas9 in sea urchins supports the contention that colour is more than it seems. Here we dissect the players, and their interactions to better understand how such host factors influence a microbial colonization. This article is part of the theme issue 'Sculpting the microbiome: how host factors determine and respond to microbial colonization'. [ABSTRACT FROM AUTHOR]

Most sea urchin species are indirect developers, going through a larval stage called pluteus. The pluteus possesses its own nervous system, consisting mainly of the apical organ neurons (controlling metamorphosis and settlement) and ciliary band neurons (controlling swimming behavior and food collection). Additional neurons are located in various areas of the gut. In recent years, the molecular complexity of this apparently "simple" nervous system has become apparent, with at least 12 neuronal populations identified through scRNAsequencing in the species Strongylocentrotus purpuratus. Among these, there is a cluster of neurosecretory cells that produce a thyrotropin-releasing hormone-type neuropeptide (TRHergic) and that are also photosensory (expressing a Go-Opsin). However, much less is known about the organization of the nervous system in other sea urchin species. The aim of this work was to thoroughly characterize the localization of the TRHergic cells from early pluteus to juvenile stages in the Mediterranean sea urchin species Paracentrotus lividus combining immunostaining and whole mount in situ hybridization. We also compared the localization of TRHergic cells in early plutei of two other sea urchin species, Arbacia lixula and Heliocidaris tuberculata. This work provides new information on the anatomy and development of the nervous system in sea urchins. Moreover, by comparing the molecular signature of the TRHergic cells in P. lividus and S. purpuratus, we have obtained new insights how TRH-type neuropeptide signaling evolved in relatively closely related species. [ABSTRACT FROM AUTHOR]

microRNAs are evolutionarily conserved non-coding RNAs that direct post-transcriptional regulation of target transcripts. In vertebrates, microRNA-1 (miR-1) is expressed in muscle and has been found to play critical regulatory roles in vertebrate angiogenesis, a process that has been proposed to be analogous to sea urchin skeletogenesis. Results indicate that both miR-1 inhibitor and miR-1 mimic-injected larvae have significantly less F-actin enriched circumpharyngeal muscle fibers and fewer gut contractions. In addition, miR-1 regulates the positioning of skeletogenic primary mesenchyme cells (PMCs) and skeletogenesis of the sea urchin embryo. Interestingly, the gain-of-function of miR-1 leads to more severe PMC patterning and skeletal branching defects than its loss-of-function. The results suggest that miR-1 directly suppresses Ets1/2, Tbr, and VegfR7 of the skeletogenic gene regulatory network, and Nodal, and Wnt1 signaling components. This study identifies potential targets of miR-1 that impacts skeletogenesis and muscle formation and contributes to a deeper understanding of miR-1's function during development. [Display omitted] • Sea urchin miR-1 has broad expression and function in the developing embryo. • miR-1 regulates gut muscle structures. • miR-1 regulates skeletogenic cell patterning and skeletal spicules. • miR-1 is likely to directly suppress skeletogenic gene regulatory components. This study identifies miR-1 to regulate circumpharyngeal muscle structure, skeletal branching, and skeletal cell patterning. Using site directed mutagenesis and reporter constructs, we identified that miR-1 directly suppresses Ets1/2, Tbr, and VegfR7 of the skeletogenic gene regulatory network, and Nodal, Notch, and Wnt1 signaling components. [ABSTRACT FROM AUTHOR]

The mass mortality event of the herbivorous sea urchin Diadema antillarum in 1983--1984 has been a major contributor to the diminished resilience of coral reefs throughout the Caribbean. The reduction in grazing pressure resulted in algae proliferation, which inhibited coral recruitment after disturbances such as disease, hurricanes, pollution and climatic change induced marine heat waves. Natural recovery of D. antillarum after the 1983--1984 die-off has been slow. However, the few locations with recovered populations exhibit signs of improvement in coral reef health, prompting interest in D. antillarum restoration. Current restoration strategies include translocation of wild individuals, the restocking of juveniles that are either cultured from gametes or collected as settlers and head-started in a nursery, and assisted natural recovery by providing suitable settlement substrate. Both the collection of wild settlers and assisted natural recovery necessitate an understanding of the local, spatiotemporal trends in settlement. In this study, which was carried out on the Dutch Caribbean Island of Saba, artificial turf settlement collectors were deployed at nine locations around the island and monitored from June 2019 till July 2020 (13 months). The primary objective was to identify trends in larval settlement in space and time, to be able to optimize restoration efforts. Additionally, the small size of Saba allowed us to deploy settlement collectors around the island and compare D. antillarum settlement between windward and leeward sides. Our study showed that on Saba, D. antillarum settlement peaked in June and July, following similar seasonal trends observed around other islands in the Northeastern Caribbean. By far the most settlement occurred at the leeward side of the island, suggesting that hydrodynamic forces entrained D. antillarum larvae in the lee of Saba and/or calmer waters facilitated settlement. Limited settlement occurred on the more exposed windward locations. The identified high settlement locations are candidates for settler collection and restoration attempts. Continued monitoring of D. antillarum settlement, especially in light of the 2022 D. antillarum die-off, holds significance as it can provide insights into the potential of natural recovery. [ABSTRACT FROM AUTHOR]

[Display omitted] The preservation of marine ecosystems and the safety of harvested seafood have elicited global concern. In this study, we evaluated bacterial contamination levels in sea urchin Paracentrotus lividus gonads with relation to environmental factors and the physicochemical parameters of seawater. This investigation aimed to assess bacterial contamination levels of Total Aerobic Mesophilic Bacteria (TAMB), Enterobacteriaceae (ETB), Fecal Coliforms (FC), Staphylococcus aureus (STAPH), Escherichia coli (E. coli), and Salmonella spp. (SALM) in sea urchin gonads collected from the Tangier coast between December 2020 and November 2021, per Moroccan regulations (NM 08.7.040). Twenty-one physicochemical, environmental, and biological parameters were assessed in 360 samples of P. lividus from four seasons. The results of these parameters were processed using multivariate statistical approaches. It was found that almost all biological parameters had concentrations below Moroccan regulatory limits, except for FC in July (173 CFU/g). Furthermore, E. coli and SALM were absent. Principal component analysis (PCA) demonstrated that the F1 component was associated with a combination of environmental, microbiological, and anthropogenic factors. These associations contributed to 59.02% of all data variations and were strongly influenced by seasonality. The F2 component contributed to 26.33% of all data variations. These findings may aid decision-makers in the protection of public health in sensitive locations such as the Tangier coast in northern Morocco. [ABSTRACT FROM AUTHOR]

Background: Some marine invertebrate organisms are considered not to develop tumors due to unknown mechanisms. To gain an initial insight into how tumor‐related genes may be expressed and function during marine invertebrate development, we here leverage sea urchin embryos as a model system and characterize the expressions of Myc and p53/p63/p73 which are reported to function synergistically in mammalian models as an oncogene and tumor suppressor, respectively. Results: During sea urchin embryogenesis, a combo gene of p53/p63/p73 is found to be maternally loaded and decrease after fertilization both in transcript and protein, while Myc transcript and protein are zygotically expressed. p53/p63/p73 and Myc proteins are observed in the cytoplasm and nucleus of every blastomere, respectively, throughout embryogenesis. Both p53/p63/p73 and Myc overexpression results in compromised development with increased DNA damage after the blastula stage. p53/p63/p73 increases the expression of parp1, a DNA repair/cell death marker gene, and suppresses endomesoderm gene expressions. In contrast, Myc does not alter the expression of specification genes or oncogenes yet induces disorganized morphology. Conclusions: p53/p63/p73 appears to be important for controlling cell differentiation, while Myc induces disorganized morphology yet not through conventional oncogene regulations or apoptotic pathways during embryogenesis of the sea urchin. Key Findings: p53/p63/p73 protein is maternally loaded, while Myc protein expression starts zygotically.p53/p63/p73 and Myc proteins are localized in the cytoplasm and nucleus of all blastomeres, respectively, during early embryogenesis.Overexpression of p53/p63/p73 and Myc increases their nuclear localization and DNA damage in the resultant embryos.p53/p63/p73 appears to suppress gene expressions for cell specification differentiation, while Myc has no impact on specification genes yet causes disorganized morphology and embryonic death. [ABSTRACT FROM AUTHOR]

IntroductionIn recent decades, Caribbean coral reefs have lost many vital marine species due to diseases. The well-documented mass mortality event of the long-spined black sea urchin Diadema antillarum in the early 1980s stands out among these collapses. This die-off killed over 90% of D. antillarum changing the reefscape from coral to algal-dominated. Nearly 40 years later, D. antillarum populations have yet to recover. In early 2022, a new mortality event of D. antillarum was reported along the Caribbean, including Puerto Rico.MethodsThis study identifies the gut microbiota changes associated with the D. antillarum during this mortality event. It contrasts them with the bacterial composition of gut samples from healthy individuals collected in 2019 by using 16S rRNA sequencing analyses.ResultsNotably, the die-off group’s core microbiome resembled bacteria commonly found in the human skin and gut, suggesting potential anthropogenic contamination and wastewater pollution as contributing factors to the 2022 dysbiosis. The animals collected in 2022, especially those with signs of disease, lacked keystone taxa normally found in Diadema including Photobacterium and Propionigenium.DiscussionThe association between human microbes and disease stages in the long-spined urchin D. antillarum, especially in relation to anthropogenic contamination, highlights a complex interplay between environmental stressors and marine health. While these microbes might not be the direct cause of death in this species of sea urchins, their presence and proliferation can indicate underlying issues, such as immune depletion due to pollution, habitat destruction, or climate change, that ultimately compromise the health of these marine organisms.

Sea urchin (Mesocentrotus nudus) is a commercially significant mariculture species, with its gonads being the exclusive edible parts for humans. Identifying sex-related genes is an effective approach for elucidating the underlying molecular mechanisms of gonad development in sea urchins. Some cytochrome P450 (CYP) superfamily members play critical roles in sex differentiation, steroid hormone biosynthesis, and ovarian steroidogenesis. In the present study, we identified 83 CYPs assigned to 17 families from the gonadal transcriptomic data of M. nudus, with most CYPs clustering within the CYP 2 family branches. Furthermore, we identified 11 gender-biased CYPs, including CYP 17A1, CYP 2, CYP 3A24, CYP 4V2, and CYP 46A1, as well as 11 CYPs related to steroid hormone biosynthesis, including CYP 1A1, CYP 1A5, CYP 3, and CYP 17A1. The expression patterns of those candidate sex-related CYP genes were also analyzed. The findings lay the foundation for further investigating the role of CYPs in the endogenous synthesis of sex steroids, offering valuable insights into the molecular mechanisms underlying sex differentiation in sea urchins.

AbstractThe complete mitochondrial genomes of two spine-color individuals, red and white, of the tropical sea urchin species Tripneustes gratilla (Linnaeus, 1758) were sequenced on Illumina system platform. The red-spined species had a genome size of 15,774 bp, while the white-spined species had a genome size of 15,723 bp. Both genomes contained 13 protein-coding genes, 2 rRNA genes, and 22 tRNA genes. The GC composition in both species was above 40%. In order to investigate the phylogenetic relationships of two different spine-color individuals, a comprehensive analysis was conducted using eight complete mitochondrial genomic sequences of the genus Tripneustes on the software MEGA X. It was observed that the two spine color types of T. gratilla species showed a high similarity of 98.91%. However, different color-spined species of T. gratilla were found in separate branches of the phylogenetic tree of the same sea urchin species.

An important goal of many studies in molecular ecology is to utilize molecular tools to elucidate how critical traits like metabolism and growth are affected by environmental stressors and how organisms offset these stresses by adaptive molecular‐level responses. Stress from food deprivation may be critical for early developmental stages that require a continued supply of substrates for energy metabolism and growth if development is to be completed. In a 'From the Cover' article in this issue of Molecular Ecology, Li et al. (2023) examined the effects of withholding food (unicellular algae) on 10 traits of larvae of the purple sea urchin (Strongylocentrotus purpuratus), ranging from the molecular level (gene expression) to morphology. Overall, this study sheds new light on the plasticity of larval development and the tight linkages that exist among traits as they respond to changes in food availability. Importantly, shifts in the sources of food utilized under different dietary treatments show the plasticity of these larvae to alter reliance on endogenous energy stores and dissolved organic matter (DOM) as algae deprivation continues. The effects of global change on the amounts and phenology of productivity in the seas make this type of integrated, multi‐level analysis an important tool for predicting the future states of marine ecosystems. [ABSTRACT FROM AUTHOR]

Bacterial assemblages associated with sea urchin are critical to their physiology and ecology within marine ecosystems. In this study, we characterized the bacterial communities in wild sea urchin Anthocidaris crassispina captured in Daya Bay, South China Sea. A total of 363 amplicon sequence variants belonging to nine phyla and 141 genera were classified from intestine, body surface, and surrounding seawater samples. Proteobacteria, Firmicutes, and Bacteroidetes were the dominant bacteria phyla found in this study. A network analysis of bacterial interspecies interactions revealed varying complexity, stability, connectivity, and relationship patterns across the samples, with the most intricate network observed in the surrounding seawater. Metagenomic predictions highlighted the distinct bacterial metabolic pathways, with significant differences between intestine and seawater samples. Notably, pathways associated with polysaccharide degradation, including chitin derivatives, starch, and CoM biosynthesis, were markedly abundant, underscoring the gut microbiota’s key role in digesting algae. In addition, other metabolic pathways in intestine samples were linked to immune response regulation of sea urchins. Overall, this study provides a comprehensive overview of the bacterial community structure and potential functional roles in A. crassispina.

Simple Summary: Differing light color environments can have inhibitory and promotional effects on the growth of aquatic life. We aimed to determine the optimal light color composition that promotes the growth and development of Tripneustes gratilla and provide valuable basic insights for the large-scale cultivation of sea urchins in China. The sea urchins exhibited improved growth and feeding performance under blue and green light conditions, and the sea urchin organisms were in better physiological condition under blue light. In contrast, red light had a significant inhibitory effect on the feeding and growth rates of the sea urchins. These differences may differentially affect the development and reproduction of sea urchins, with sea urchins being more suited to growth and development under blue light, followed by white and green light, and not suited to development and reproduction under red light. Studying the impact of light color on the digestive and antioxidant processes of sea urchins is essential to decrease physiological stress and enhance the well-being of farmed sea urchins. To study the effects of light color on sea urchin (Tripneustes gratilla), blue light (B, λ450nm), yellow light (Y, λ585–590nm), red light (R, λ640nm), green light (G, λ510nm), white light (W, λ400–780nm), and darkness (H) groups were established in a recirculating seawater aquaculture system. Six different LED light color treatment groups with a photoperiod of 12 L:12 D were tested for 30 days to investigate the effects of different light colors on the feeding, growth, and enzyme activities of T. gratilla (142.45 ± 4.36 g). We found that using different LED light colors caused significantly different impacts on the feeding, growth, and enzyme activity of T. gratilla. Notably, the sea urchins in group B exhibited better growth, with a weight gain rate of 39.26%, while those in group R demonstrated poorer growth, with a weight gain rate of only 26%. The feeding status differed significantly (p < 0.05) between groups B and R, with group B consuming the highest daily intake (6.03 ± 1.69 g) and group R consuming the lowest (4.54 ± 1.26 g). Throughout the three phases, there was no significant change in the viability of the α-amylase (p > 0.05). Conversely, the pepsin viability significantly increased (p < 0.05) in group B. The lipase viability consistently remained at the lowest level, with no notable differences between group W and group B. In group R, both the α-amylase and pepsin viabilities remained lower, whereas the lipase viability was noticeably greater in each phase than in group B (p < 0.05). Among the antioxidant enzymes, group R exhibited a trend of initial increase followed by decreases in catalase, superoxide dismutase, and glutathione peroxidase activities, particularly during the third stage (15–30 days), during which a significant decrease in antioxidant enzyme activity was observed (p < 0.05). Taken together, these findings suggest that blue light positively affects the growth, feeding, digestion, and antioxidant capacity of T. gratilla in comparison with those in other light environments, whereas red light had an inhibitory effect. Furthermore, T. gratilla is a benthic organism that lives on shallow sandy sea beds. Thus, as short wavelengths of blue and green light are more widely distributed on the seafloor, and long wavelengths of red light are more severely attenuated on the seafloor, shorter wavelengths of light promote the growth of bait organisms of sea urchins, which provide better habitats for T. gratilla. [ABSTRACT FROM AUTHOR]