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Abstract Background The Caribbean spiny lobster Panulirus argus is heavily fished throughout its Greater Caribbean and Gulf of Mexico distribution, suggesting a heightened susceptibility to a fisheries collapse. In 2017, a nemertean worm, Carcinonemertes conanobrieni was described from ovigerous females of P. argus in Florida, USA. A year later, the presence of the same egg predator was recorded along the southern Caribbean coast (Colombia). The effect of this egg predator on the reproductive performance, including fecundity, embryo mortality, and reproductive output, of its host is unknown. This study tested whether C. conanobrieni affects embryo mortality, fecundity, and reproductive output in brooding females of P. argus. Results Artisan fishers caught 90 ovigerous lobsters near Pueblo Viejo, Magdalena, Colombia. Each ovigerous female was examined for the presence/absence of the egg predator. Lobster egg mortality (%), fecundity (nº eggs female−1), and reproductive output (%) were estimated. Prevalence of C. conanobrieni in the studied population was 87.78%. The mean intensity of C. conanobrieni (all life stages) in the population was 11.68 (± 1.98) egg predators per brood mass sample. Infected females brooding late-stage embryos exhibited lower fecundity, lower reproductive performance values, and higher embryo mortality compared to infected females brooding early-stage embryos. Embryo stage and worm infection level negatively impacted fecundity and reproductive output. Worm infection level and the number of adult nemertean worms also negatively affected embryo mortality. Conclusions These results demonstrate an adverse effect of C. conanobrieni on the reproductive performance of P. argus. The interactive impact of this egg predator, natural stressors, and anthropogenic stressors on individual P. argus reproductive performance could facilitate losses at large-scale fisheries levels.

Some, probably most and perhaps all, members of the phylum Nemertea are poisonous, documented so far from marine and benthic specimens. Although the toxicity of these animals has been long known, systematic studies on the characterization of toxins, mechanisms of toxicity, and toxin evolution for this group are scarce. Here, we present the first investigation of the molecular evolution of toxins in Nemertea. Using a proteo-transcriptomic approach, we described toxins in the body and poisonous mucus of the pilidiophoran Lineus sanguineus and the hoplonemertean Nemertopsis pamelaroeae. Using these new and publicly available transcriptomes, we investigated the molecular evolution of six selected toxin gene families. In addition, we also characterized in silico the toxin genes found in the interstitial hoplonemertean, Ototyphlonemertes erneba, a meiofaunal taxa. We successfully identified over 200 toxin transcripts in each of these species. Evidence of positive selection and gene duplication was observed in all investigated toxin genes. We hypothesized that the increased rates of gene duplications observed for Pilidiophora could be involved with the expansion of toxin genes. Studies concerning the natural history of Nemertea are still needed to understand the evolution of their toxins. Nevertheless, our results show evolutionary mechanisms similar to other venomous groups. [ABSTRACT FROM AUTHOR]

Background: The Caribbean spiny lobster Panulirus argus is heavily fished throughout its Greater Caribbean and Gulf of Mexico distribution, suggesting a heightened susceptibility to a fisheries collapse. In 2017, a nemertean worm, Carcinonemertes conanobrieni was described from ovigerous females of P. argus in Florida, USA. A year later, the presence of the same egg predator was recorded along the southern Caribbean coast (Colombia). The effect of this egg predator on the reproductive performance, including fecundity, embryo mortality, and reproductive output, of its host is unknown. This study tested whether C. conanobrieni affects embryo mortality, fecundity, and reproductive output in brooding females of P. argus. Results: Artisan fishers caught 90 ovigerous lobsters near Pueblo Viejo, Magdalena, Colombia. Each ovigerous female was examined for the presence/absence of the egg predator. Lobster egg mortality (%), fecundity (nº eggs female−1), and reproductive output (%) were estimated. Prevalence of C. conanobrieni in the studied population was 87.78%. The mean intensity of C. conanobrieni (all life stages) in the population was 11.68 (± 1.98) egg predators per brood mass sample. Infected females brooding late-stage embryos exhibited lower fecundity, lower reproductive performance values, and higher embryo mortality compared to infected females brooding early-stage embryos. Embryo stage and worm infection level negatively impacted fecundity and reproductive output. Worm infection level and the number of adult nemertean worms also negatively affected embryo mortality. Conclusions: These results demonstrate an adverse effect of C. conanobrieni on the reproductive performance of P. argus. The interactive impact of this egg predator, natural stressors, and anthropogenic stressors on individual P. argus reproductive performance could facilitate losses at large-scale fisheries levels. [ABSTRACT FROM AUTHOR]

The implementation of molecular data for the analysis of nemertean diversity has unraveled the taxonomic status of several species and many higher taxa within the group. Nowadays, a large proportion of novel putative species are being discovered and it is necessary to add molecular data to the morphological description to obtain a correct identification. In this study, we used mitochondrial cytochrome oxidase I gene (COI) as molecular marker to investigate the diversity of nemerteans from a marine Sub-Antarctic environment. We used Automatic Barcode Gap Discovery (ABGD), Poisson Tree Processes (PTP) and Bayesian implementation of the PTP model (bPTP) as well as reciprocal monophyly on neighbor-joining (NJ) and maximum likelihood (ML) trees for species delimitation. ABGD showed a clear barcoding gap (6 to 10%) and the presence of 15 different putative nemertean species in the dataset of 54 COI sequences from the marine protected area "Namuncurá–Burdwood Bank" (MPA-BB), expanding the known biodiversity for the Sub-Antarctic region. Ten monostiliferan and five heteronemertean species were found. Our results also confirm the presence of two Parborlasia corrugatus cryptic species in the Antarctic and Sub-Antarctic region. This work highlights the importance of the MPA-BB as a biodiversity hotspot and provide molecular data for the Phylum Nemertea in the Southwestern Atlantic Ocean. [ABSTRACT FROM AUTHOR]

The taxonomy of ribbon worms (Nemertea) is particularly challenging due to the sparsity of distinct morphological characters, causing a significant underestimation of the group’s true diversity. The number of named deep-sea species is very limited and there is a vast number of undescribed deep-sea nemerteans still to be discovered. In this paper we figuratively ‘cut the ribbon’ and name seven new species of monostiliferous hoplonemerteans from seeps and seamounts along the Costa Rican margin, one from seeps along the Oregon margin, and one from vents of the Juan de Fuca Ridge, USA. The species Chernyshevia escarpiaphila gen. et sp. nov. and five species of the genus Alvinonemertes gen. nov. (Alvinonemertes dariae gen. et sp. nov., Alvinonemertes dagmarae gen. et sp. nov., Alvinonemertes christianeae gen. et sp. nov., Alvinonemertes claudiae gen. et sp. nov., Alvinonemertes tatjanae gen. et sp. nov.) represent Oerstediina, whereas the three species Tetrastemma sundbergi sp. nov., Tetrastemma polyakovae sp. nov., and Tetrastemma strandae sp. nov. represent Amphiporina. One species of tubulanid palaeonemerteans is described but not provided with a species name due to lacking sequence data for comparison. Additionally, we provide sequence data for one lineid heteronemertean, one reptant hoplonemertean, and two further eumonostiliferan hoplonemertean species. We use an integrative, turbotaxonomic approach combining DNA sequence data with concise morphological descriptions and fully digitized serial histological sections made available as cybertypes.

Nemertea is a phylum of nonsegmented worms (supraphylum: Spiralia), also known as ribbon worms. The members of this phylum contain various toxins, including peptide toxins. Here, we provide a transcriptomic analysis of peptide toxins in 14 nemertean species, including Cephalothrix cf. simula, which was sequenced in the current study. The summarized data show that the number of toxin transcripts in the studied nemerteans varied from 12 to 82. The most represented groups of toxins were enzymes and ion channel inhibitors, which, in total, reached a proportion of 72% in some species, and the least represented were pore-forming toxins and neurotoxins, the total proportion of which did not exceed 18%. The study revealed that nemerteans possess a much greater variety of toxins than previously thought and showed that these animals are a promising object for the investigation of venom diversity and evolution, and in the search for new peptide toxins. [ABSTRACT FROM AUTHOR]

The heteronemertean Cerebratulus marginatus Renier, 1804 is a well-known representative of the family Lineidae (Nemertea) inhabiting sandy or muddy sediments throughout the world. Due to its wide geographic distribution and the lack of distinctive external morphological features among different populations, the species has been considered cosmopolitan. Increasing evidence indicates that nemertean species, including Cerebratulus marginatus, described based on morphology are often not supported by genetic data and represent complexes of cryptic species, rather than cosmopolitan species. Here, we use species delimitation and phylogenetic analyses to evaluate the speciation patterns within the putative C. marginatus species complex. We examined 25 specimens morphologically ascribed to C. marginatus and closely related species using a multilocus dataset including two mitochondrial markers (16S rRNA, COI) and three nuclear markers (18S rRNA, 28S rRNA, H3). Our analyses identified at least four supported independent lineages among the populations analysed, indicating that samples identified as C. marginatus might represent indeed a complex of cryptic species. Therefore, our results do not support the cosmopolitanism of C. marginatus and provide additional evidence suggesting that species identifications in nemerteans should not be based exclusively on morphological or anatomical features which do not accurately reflect evolutionary patterns. Our study highlights the importance of including molecular data in addition to morphological information to accurately delimit species boundaries, thereby improving nemertean taxonomy by providing a more accurate picture of the true species diversity and geographic distribution of this typically neglected phylum. [ABSTRACT FROM AUTHOR]

The deep-water bathypelagic nemertean Nectonemertes mirabilis, previously found in the Atlantic and Pacific oceans, was confirmed for the first time in the Gulf of Mexico. This new record is represented by a juvenile male collected by a stratified plankton sampling at 800-1,000 m depth in the southern gulf (20.5°N, 94.5°W), during summer 2014. This is the first record of a pelagic nemertean in the gulf; extending our knowledge about the species' global distribution, the number of nemertean species present in Mexican Atlantic waters, and the need to explore the mesopelagic zone of the oceans. [ABSTRACT FROM AUTHOR]

We report two new, curious records of freshwater worms collected in the Panama Canal, Panama: the ribbon worm, Apatronemertes albimaculosa Wilfert and Gibson, 1974, and the leech, Placobdella parasitica (Say, 1824). Identification of these specimens relied on morphological examinations and, more heavily, on molecular barcoding using the mitochondrial COI locus. Both phylogenetic and genetic distance analyses were employed to robustly establish the identities of the specimens. Whereas the native range of A. albimaculosa is currently unknown, P. parasitica was first described from Minnesota, USA and is possibly native to southern Canada and most of the USA. Neither species has previously been recorded from Central America. We briefly discuss possible scenarios for the dispersal of both species, and conclude that the introduction of P. parasitica into Panamanian waters was likely human-mediated in association with the introduction of its turtle host. Insofar as ours is the first record of wild-caught A. albimaculosa worldwide, we do not exclude the possibility of Panama being within the native range of the species. However, it is also possible that the species has been transported with ballast water into the Panama Canal; a relatively common phenomenon. [ABSTRACT FROM AUTHOR]

Carcinonemertes conanobrieni Simpson, Ambrosio & Baeza, 2017, an egg predator of the spiny lobster Panulirus argus (Latreille, 1804), is recorded for the first time in Colombian waters and the Caribbean. Worms were isolated from an egg mass of a lobster caught at the Gulf of Salamanca, Magdalena. Little is known about the distribution of this species and currently this record from the Caribbean Coast of Colombia is the only one outside of the Florida Keys, USA. The new record suggests that this parasite might be present in the entire Caribbean Sea. [ABSTRACT FROM AUTHOR]

The heteronemertean genusLineusSowerby, 1806 has been badly in need of revision because of its apparent non-monophyly. In this paper, we focus onLineus torquatusCoe, 1901, one of the heteronemertean species that occur commonly in waters around the North Pacific, as well as a few other allied species distributed in the western North Pacific, includingLineus alborostratusTakakura, 1898 andCerebratulus montgomeryiCoe, 1901. Based on phylogenetic analyses using16S,COI,28S,18S, andH3gene andITSsequences, we detected a well-supported clade comprised of heteronemerteans with a frontal white band on the head, to which we addKulikoviagen. nov. This genus is nested within a more comprehensive, highly supported clade, here named theSiphonenteron-clade, which containsTenuilineus bicolour(Verrill, 1892),Lineus flavescensCoe, 1905,Siphonenteron bilineatum(Renier, 1804),S.cf.bilineatum,Lineuscf.caputornatus, andLineussp. from Guam. Our analyses confirmed the presence of a cryptic species of what was formerly known as the cherry-red and reddish forms ofLineus torquatus, herein described asKulikovia manchenkoisp. nov. based on some external characters, internal morphology, and the four genetic markers (COI,16S,H3, andITS). In contrast to the species pairK. torquata–K. manchenkoi, the reddish form ofK. alborostratadoes not differ genetically from the typical form of this species. The significance of the external and internal characters for distinguishing cryptic species is discussed. http://zoobank.org/urn:lsid:zoobank.org:pub:9BECBC60-9C82-48EC-AD36-FC564D82A5BChttp://zoobank.org/urn:lsid:zoobank.org:act:D02B2339-4F65-4517-9B13-DD4AAB0C55C5http://zoobank.org/urn:lsid:zoobank.org:act:8D239B62-E655-4721-90F0-A4944DD8A3C7 [ABSTRACT FROM AUTHOR]

We sequenced the complete mitochondrial genome of the Heteronemertea species, Micrura ignea . The genome was amplified with a combination of short and long PCRs that were subjected to 454 sequencing. The mitogenome of M. ignea is a circular molecule of 15,333 bp in size and encodes the 37 genes typically found in metazoans, and one non-coding region. The order of the genes is the same as for all the other Heteronemerteans. All genes are encoded on the heavy strand except trnT and trnP. The phylogenetic analyses recovered M. ignea as a basal taxon in the Lineidae family, no differences were found in the topology of the phylogenetic trees in comparison with previous studies. [ABSTRACT FROM AUTHOR]

In various discussions on the phylogenetic position of the Nemertea, nephridial morphology seems to support current hypotheses for a close relationship to lophotrochozoan subtaxa. These arguments are based on isolated findings and suffer from the lack of a phylogeny-based inference. In order to fill in this gap, the structure of the nemertean nephridia is reviewed. Based on the structural data presently available for nemertean nephridia, 30 characters are described. Their ancestral states are inferred from cladograms derived from recent molecular analyses. According to these, paired protonephridia restricted to the foregut region and associated with the blood vascular system represent the primary state in nemerteans. The terminal cells are covered by the blood vessel endothelium and have no open connection to the lumen of the blood vascular system. Serially arranged protonephridia that could support the hypothesis of an annelid-nemertean-relationship are either apomorphic for Cephalothricidae, a nemertean subgroup, or a cephalothricid ingroup. [ABSTRACT FROM AUTHOR]

Most ribborn worms (phylum Nemertea) are marine and only 22 of the currently named around 1,200 species are known from freshwater habitats (mainly lakes/ponds). They are all free-living benthic forms found in all continents except Antarctica. The vast majority of species have been recorded from the Palearctic region, but this may reflect sampling efforts rather than biogeography. [ABSTRACT FROM AUTHOR]

The valenciniid heteronemertean Baseodiscus delineatus (Delle Chiaje, 1825) was originally described from Naples, Italy, and shows a circumglobal distribution from tropical to temperate seas in both hemispheres. To investigate its reproductive biology, we performed intermittent year-round sampling from 2014 to 2018 in Misaki on the Pacific coast of Honshu, Japan. Of the 40 specimens obtained, 11 were males, while 29 were immature. No female specimen was confirmed during the sampling period. We additionally observed that B. delineatus is fissiparous. A male individual in captivity reproduced asexually by spontaneous posterior fragmentation, an ability that is described here for the first time among Valenciniidae. Autotomy occurred every 2-10 days, with each of the tail fragments having undergone anterior regeneration, which took about 24-36 days before completion of internal organs, such as ocelli, cerebral organs, brain, alimentary canal, rhynchocoel, and proboscis. A review of the literature suggests that the species was absent in the Misaki region 120 years ago. We assume a recent settlement of a male founder, which has putatively reproduced asexually to yield a clonal, unisexual population in Misaki.