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The uptake potential of fragrance encapsulates by aquatic or terrestrial organisms was investigated. Because of their size of5 mm and their polymeric nature, fragrance encapsulates fall under the Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection definition of microplastics. After use, fragrance encapsulates enter the sewer system and reach the sewage treatment plant (STP), where90% of them are likely to be removed by sorption to the sludge. When the STP-generated sludge is used as fertilizer for agricultural soils, this may lead to potential exposure of terrestrial invertebrates to fragrance encapsulates, especially those feeding on particles of a similar size as the fragrance encapsulates. Two aquatic (Corbicula fluminea [water exposure] and Hyalella azteca [water and dietary exposure]) and one terrestrial invertebrate (Eisenia andrei [soil exposure]) species were exposed to 50 mg/L (or mg/kg) double fluorescence-labeled fragrance encapsulates (diameter 5-50 µm). The results showed that fragrance encapsulates are available to aquatic and terrestrial invertebrates but that species-specific differences regarding the ability to ingest fragrance encapsulates may exist. The benthic grazer H. azteca showed no ingestion of fragrance encapsulates, whereas the capsules were readily ingested and egested by the unselective freshwater filter feeder C. fluminea as well as the terrestrial decomposer E. andrei. No signs of bioaccumulation of fragrance encapsulates were indicated by microscopic assessment. Environ Toxicol Chem 2022;41:931-943. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Assessing the conservation status of a species is strongly dependent upon data on species distribution and abundance. With the emergence of novel methods for species monitoring – such as the use of environmental DNA (eDNA) – monitoring success can be improved at reduced expenditure in the field, particularly in remote regions and terrains where access is difficult or dangerous. The highly endangered crocodile lizard (Shinisaurus crocodilurus Ahl, 1930) inhabits fragmented sites of the remaining evergreen forest with running water systems in a narrow distribution range in southern China and north‐east Vietnam. Crocodile lizards spend most of the day within or above water bodies, which are commonly remote and inaccessible. To monitor recent spatial occurrences, and to confirm the persistence or extinction of previously reported populations (especially in heavily altered habitats), the suitability of using eDNA and quantitative polymerase chain reaction (qPCR) was tested as an alternative method for monitoring this semiaquatic lizard. To assess the accuracy and limitations of this method, eDNA results from the field were compared with eDNA data from mesocosms and census data on the actual abundance of this species in the field. Environmental DNA of the crocodile lizard was detected in all of the positive controls, and in four of six natural sites; thus, all data collected using traditional field surveys were confirmed with eDNA results. eDNA monitoring was found to be a reliable method for assessing the viability of populations; we suggest that it should be developed as a tool for efficient wildlife management, particularly under difficult field and funding conditions.

Eicosanoids are an important class of signalling molecules derived from essential polyunsaturated fatty acids (PUFAs). Some recent research had started to investigate the eicosanoid pathway in Daphnia magna, but focussed mostly on the role of omega-6 PUFAs, rather than on the nutritionally important omega-3 PUFA eicosapentaenoic acid (EPA), which is known to determine the trophic transfer efficiency from phytoplankton to cladoceran zooplankton in freshwater foodwebs. To test for the relevance of EPA for the expression of genes in the eicosanoid pathway, we conducted highly controlled feeding experiments with D. magna under two temperature conditions and supplemented diets differing only in their EPA contents. Some, but not all genes previously reported to be related to the eicosanoid metabolism of D. magna, were significantly upregulated when EPA was available in the diet. Other genes from the eicosanoid pathway and two control genes not related to eicosanoid metabolism were unaffected by dietary EPA availability. Our data demonstrate that dietary omega-3 PUFA availability affects the expression of some genes typically considered to be part of the omega-6 PUFA-dependent eicosanoid metabolism. These findings may thus advance our understanding of the biochemical physiology of this essential dietary compound and its role for zooplankton nutrition.

It is widely accepted that in many food webs, the trophic transfer efficiency among primary producers and herbivores is determined by the nutritional value of primary producers. In pelagic freshwater and marine ecosystems, secondary production by herbivorous crustacean zooplankton is often limited by the seston's content of essential ω3 polyunsaturated fatty acids (ω3 PUFAs). However, little is known about the genetic network behind the positive relationship between phytoplankton ω3 PUFA content and zooplankton growth and reproduction. In our experimental study, we analysed gene expression changes of the freshwater cladoceran Daphnia magna under different food regimes differing in their ω3 PUFA composition. To disentangle ω3 PUFA effects from other factors, we fed D. magna with different pure phytoplankton cultures (i.e., algal and cyanobacterial diets) with or without supplementing the essential ω3 PUFA eicosapentaenoic acid (EPA). As hypothesized, we observed enhanced growth on diets supplemented with EPA. We applied an Illumina RNA-seq approach to D. magna from different diet treatments to find and monitor genes that are regulated dependent on EPA availability. Of 26,646 potential protein products (mapped to the D. magna genome), we identified transcriptomic signatures driven by the different food sources. Further analyses revealed specific candidate genes involved in EPA metabolism, irrespective of the basal food source. This allows a first functional annotation of previously uncharacterized genes involved in the EPA-specific response of D. magna and may finally provide a link to molecular processes connected to ω3 PUFA metabolism and conversion and thus trophic transfer efficiency in pelagic food webs.

BackgroundNutritional quality of phytoplankton is a major determinant of the trophic transfer efficiency at the plant-herbivore interface in freshwater food webs. In particular, the phytoplankton’s content of the essential polyunsaturated omega-3 fatty acid eicosapentaenoic acid (EPA) has been repeatedly shown to limit secondary production in the major zooplankton herbivore genusDaphnia. Despite extensive research efforts on the biological model organismDaphnia, and the availability of severalDaphniagenomes, little is known regarding the molecular mechanisms underlying the limitations inDaphniarelated to dietary EPA availability.ResultsWe used RNA-seq to analyse the transcriptomic response ofDaphnia magnawhich were fed with two different diets — each with or without supplementation of EPA — at two different temperature levels (15 and 20 °C). The transcripts were mapped to theD. magnagenome assembly version 2.4, containing 26,646 translations. WhenD. magnafed on green alga, changing the temperature provoked a differential expression of 2001 transcripts, and in cyanobacteria-fed daphnia, 3385 transcripts were affected. The supplementation of EPA affected 1635 (on the green algal diet), or 175 transcripts (on the cyanobacterial diet), respectively. Combined effects for diet and temperature were also observed (669 for the green algal and 128 transcripts for the cyanobacterial diet). Searching for orthologous genes (COG-analysis) yielded a functional overview of the altered transcriptomes. Cross-matched transcript sets from both feed types were compiled to illuminate core responses to the factors temperature and EPA-supplementation.ConclusionsOur highly controlled eco-physiological experiments revealed an orchestrated response of genes involved in the transformation and signalling of essential fatty acids, including eicosanoid-signalling pathways with potential immune functions. We provide an overview of downstream-regulated genes, which contribute to enhance growth and reproductive output. We also identified numerous EPA-responsive candidate genes of yet unknown function, which constitute new targets for future studies on the molecular basis of EPA-dependent effects at the freshwater plant-herbivore interface.

The non-Antarctic Notothenioidei families, Bovichtidae, Pseudaphritidae and Eleginopsidae, diverged early from the main notothenioid lineage. They are important in clarifying the early evolutionary processes that triggered notothenioid evolution in the Antarctic. The early-diverged group represents 8% of all notothenioid species and never established themselves on the Antarctic shelf. Most attention has been paid to the Antarctic notothenioids and their limited physiological tolerance to climate change and increased temperatures. In this review, we discuss key life history traits that are characteristic of the non-Antarctic early-diverged notothenioid taxa as well as the genetic resources and population differentiation information available for this group. We emphasise the population fitness and dynamics of these species and indicate how resource management and conservation of the group can be strengthened through an integrative approach. Both Antarctic waters and the non-Antarctic regions face rapid temperature rises combined with strong anthropogenic exploitation. While it is expected that early-diverged notothenioid species may have physiological advantages over high Antarctic species, it is difficult to predict how climate changes might alter the geographic range, behaviour, phenology and ultimately genetic variability of these species. It is possible, however, that their high degree of endemism and dependence on local environmental specificities to complete their life cycles might enhance their vulnerability.

Oceans are experiencing increasing acidification in parallel to a distinct warming trend in consequence of ongoing climate change. Rising seawater temperatures are mediating a northward shift in distribution of Atlantic cod (Gadus morhua), into the habitat of polar cod (Boreogadus saida), that is associated with retreating cold water masses. This study investigates the competitive strength of the co-occurring gadoids under ocean acidification and warming (OAW) scenarios. Therefore, we incubated specimens of both species in individual tanks for 4 months, under different control and projected temperatures (polar cod: 0, 3, 6, 8 °C, Atlantic cod: 3, 8, 12, 16 °C) and PCO2 conditions (390 and 1170 µatm) and monitored growth, feed consumption and standard metabolic rate. Our results revealed distinct temperature effects on both species. While hypercapnia by itself had no effect, combined drivers caused nonsignificant trends. The feed conversion efficiency of normocapnic polar cod was highest at 0 °C, while optimum growth performance was attained at 6 °C; the long-term upper thermal tolerance limit was reached at 8 °C. OAW caused only slight impairments in growth performance. Under normocapnic conditions, Atlantic cod consumed progressively increasing amounts of feed than individuals under hypercapnia despite maintaining similar growth rates during warming. The low feed conversion efficiency at 3 °C may relate to the lower thermal limit of Atlantic cod. In conclusion, Atlantic cod displayed increased performance in the warming Arctic such that the competitive strength of polar cod is expected to decrease under future OAW conditions.

In this study, we describe a de novo sequencing and assembly of the spleen transcriptome of Lepidonotothen nudifrons, a notothenioid fish widely distributed around the Antarctic Peninsula and the Scotia Arc. Sequences were generated on an Illumina MiSeq system and assembled to a total of 112,477 transcripts. Putative functional annotation was possible for more than 34% of the transcripts. This data will be relevant for future studies targeting the erythrocyte turnover, oxygen transport mechanism and immune system, which are key functional traits to investigate cold adaptation and thermal sensitivity of Antarctic notothenioids.

Research on the thermal biology of Antarctic marine organisms has increased awareness of their vulnerability to climate change, as a flipside of their adaptation to life in the permanent cold and their limited capacity to acclimate to variable temperatures. Here, we employed a species–specific microarray of the Antarctic eelpout, Pachycara brachycephalum to identify long-term shifts in gene expression after 2 months of acclimation to six temperatures between -1°C and 9°C. Changes in cellular processes comprised signalling, post-translational modification, cytoskeleton remodelling, metabolic shifts and alterations in the transcription as well as translation machinery. The magnitude of transcriptomic responses paralleled the change in whole animal performance. Optimal growth at 3°C occurred at a minimum in gene expression changes indicative of a balanced steady state. The up–regulation of ribosomal transcripts at 5°C and above was accompanied by the transcriptomic activation of differential protein degradation pathways, from proteasome-based degradation in the cold towards lysosomal protein degradation in the warmth. From 7°C upwards increasing transcript levels representing heat shock proteins and an acute inflammatory response indicate cellular stress. Such patterns may contribute to a warm-induced energy deficit and a strong weight loss at temperatures above 6°C. Together, cold or warm acclimation led to specific cellular rearrangements and the progressive development of functional imbalances beyond the optimum temperature. The observed temperature–specific expression profiles reveal the molecular basis of thermal plasticity and refine present understanding of the shape and positioning of the thermal performance curve of ectotherms on the temperature scale.

It is widely accepted that adaptation to the extreme cold has evolved at the expense of high thermal sensitivity. However, recent studies have demonstrated significant capacities for warm acclimation in Antarctic fishes. Here, we report on hepatic metabolic reorganization and its putative molecular background in the Antarctic eelpout ( Pachycara brachycephalum ) during warm acclimation to 5°C over 6 wk. Elevated capacities of cytochrome c oxidase suggest the use of warm acclimation pathways different from those in temperate fish. The capacity of this enzyme rose by 90%, while citrate synthase (CS) activity fell by 20% from the very beginning. The capacity of lipid oxidation by hydroxyacyl-CoA dehydrogenase remained constant, whereas phosphoenolpyruvate carboxykinase as a marker for gluconeogenesis displayed 40% higher activities. These capacities in relation to CS indicate a metabolic shift from lipid to carbohydrate metabolism. The finding was supported by large rearrangements of the related transcriptome, both functional genes and potential transcription factors. A multivariate analysis (canonical correspondence analyses) of various transcripts subdivided the incubated animals in three groups, one control group and two responding on short and long timescales, respectively. A strong dichotomy in the expression of peroxisome proliferator-activated receptors-1α and -β receptors was most striking and has not previously been reported. Altogether, we identified a molecular network, which responds sensitively to warming beyond the realized ecological niche. The shift from lipid to carbohydrate stores and usage may support warm hardiness, as the latter sustain anaerobic metabolism and may prepare for hypoxemic conditions that would develop upon warming beyond the present acclimation temperature.

Background Studies of temperature-induced adaptation on the basis of genomic sequence data were mainly done in extremophiles. Although the general hypothesis of an increased molecular flexibility in the cold is widely accepted, the results of thermal adaptation are still difficult to detect at proteomic down to the genomic sequence level. Approaches towards a more detailed picture emerge with the advent of new sequencing technologies. Only small changes in primary protein structure have been shown to modify kinetic and thermal properties of enzymes, but likewise for interspecies comparisons a high genetic identity is still essential to specify common principles. The present study uses comprehensive transcriptomic sequence information to uncover general patterns of thermal adaptation on the RNA as well as protein primary structure. Results By comparing orthologous sequences of two closely related zoarcid fish inhabiting different latitudinal zones (Antarctica: Pachycara brachycephalum, temperate zone: Zoarces viviparus) we were able to detect significant differences in the codon usage. In the cold-adapted species a lower GC content in the wobble position prevailed for preserved amino acids. We were able to estimate 40-60% coverage of the functions represented within the two compared zoarcid cDNA-libraries on the basis of a reference genome of the phylogenetically closely related fish Gasterosteus aculeatus. A distinct pattern of amino acid substitutions could be identified for the non-synonymous codon exchanges, with a remarkable surplus of serine and reduction of glutamic acid and asparagine for the Antarctic species. Conclusion Based on the differences between orthologous sequences from confamiliar species, distinguished mainly by the temperature regimes of their habitats, we hypothesize that temperature leaves a signature on the composition of biological macromolecules (RNA, proteins) with implications for the transcription and translation level. As the observed pattern of amino acid substitutions only partly support the flexibility hypothesis further evolutionary forces may be effective at the global transcriptome level.