A hidden lethal effect of long microplastic fibres on the coastal copepod Acartia erythraea.

We investigated the lethal effects of a long fibrous microplastic (the range of lengths, widths, and thicknesses were 1.5-3.6 mm, 10-16 µm, and 7-8.5 µm, respectively) made of polyethylene terephthalate textile, on the marine copepod Acartia erythraea. In laboratory, starved copepods were observed to take in a piece of fibrous microplastic sedimented on the bottom. While no individual ingested the entire fibre, the tip of the ingested fibre reached deep into the gut of the copepods. This suggests that ingestion was not accidental but purposeful behaviour to take in non-living organic matter as a supplementary food source. All copepods that had the fibre in their mouths eventually died within 24-h because the fibre penetrated deep into the gut, preventing feeding and potentially causing stress. Our finding implies that a single piece of microplastic fibre remaining at the bottom of coastal zones could continue to kill copepods owing to its non-degradability.

Assessment of toxic effects of imidacloprid on freshwater zooplankton: An experimental test for 27 species.

The neonicotinoid pesticide imidacloprid has been used worldwide since 1992. As one of the most important chemicals used in pest control, there have been concerns that its run-off into rivers and lakes could adversely affect aquatic ecosystems, where zooplankton play a central role in the energy flow from primary to higher trophic levels. However, studies assessing the effects of pesticides at the species level have relied on a Daphnia-centric approach, and no studies have been conducted using species-level assessments on a broad range of zooplankton taxa. In the present study, we therefore investigated the acute toxicity of imidacloprid on 27 freshwater crustacean zooplankton (18 cladocerans, 3 calanoid copepods and 6 cyclopoid copepods). The experiment showed that a majority of calanoid copepods and cladocerans were not affected at all by imidacloprid, with the exception of one species each of Ceriodaphnia and Diaphasoma, while all six cyclopoid copepods showed high mortality rates, even at concentrations of imidacloprid typically found in nature. In addition, we found a remarkable intra-taxonomic variation in susceptibility to this chemical. As many cyclopoid copepods are omnivorous, they act as predators as well as competitors with other zooplankton. Accordingly, their susceptibility to imidacloprid is likely to cause different responses at the community level through changes in predation pressure as well as changes in competitive interactions. The present results demonstrate the need for species-level assessments of various zooplankton taxa to understand the complex responses of aquatic communities to pesticide disturbance.

Spatial variability in size and lipid content of the marine copepod Calanus finmarchicus across the Northwest Atlantic continental shelves: implications for North Atlantic right whale prey quality.

Copepod size and energy content are influenced by regional and seasonal variation in temperature and food conditions, with implications for planktivorous consumers such as the endangered North Atlantic right whale (Eubalaena glacialis). Historical data (1990-2020) on Calanus finmarchicus stage CV copepodite prosome length and oil sac metrics were analyzed to determine the extent of variation in individual body size and estimated lipid and energy content in five regions of the Northwest Atlantic continental shelves [Gulf of Maine (GoM), Scotian Shelf (SS), Gulf of St. Lawrence (GSL), St. Lawrence Estuary (SLE) and Newfoundland Shelf]. Large-scale spatial patterns in size and lipid content were related to latitude, indicating that C. finmarchicus CV in the GSL and SLE were historically larger in body size, and had significantly higher lipid content compared with those in the GoM and the SS. The observed patterns of C. finmarchicus CV size and lipid storage capacity suggest that regional variation in whale prey energy content can play a role in the suitability of current and future whale foraging habitats in the Northwest Atlantic, with the larger lipid-rich individuals in the GSL providing a high-quality diet compared with those in southern areas.

Copterus tyloloricatus (Ciliophora, Suctorea), a new suctorian genus and species.

We present the description of the new suctorian genus Copterus gen. n. with type species Copterus tyloloricatus sp. n. from the family Acinetidae, inhabiting the prosomes and urosomes of calanoid copepods from the northern North Pacific Ocean. The new taxon is characterized by (i) an ellipsoidal to triangular, asymmetric, dorsoventrally flattened cell body, which lies horizontally on the lorica surface; (ii) an unflattened lorica; and (iii) the presence of three to five radially arranged bundles of tentacles positioned at the edge of the body or on actinophores.

The complete mitochondrial genome of Labidocera rotunda Mori, 1929 (Copepoda: Calanoida) from Jeju Island, Korea.

We sequenced the complete mitochondrial genome of the copepod Labidocera rotunda (family Pontellidae) collected from Ihotaewoo Beach in Jeju, Korea. The mitochondrial genome was 16,564 bp in length and contained 13 protein-coding genes (PCGs), 22 transfer RNAs, and two ribosomal RNAs. The concatenated phylogenetic tree of L. rotunda was reconstructed using the maximum-likelihood method based on the eight PCGs obtained from eight species of copepods including L. rotunda. The results of the phylogeny analysis showed that L. rotunda was closely related to the family Temoridae among the three families. The complete mitochondrial genome of L. rotunda analyzed for the first time in this study provides insight into the phylogenetic and evolutionary relationship of Labidocera.

Plankton food webs in the oligotrophic Gulf of Mexico spawning grounds of Atlantic bluefin tuna.

We used linear inverse ecosystem modeling techniques to assimilate data from extensive Lagrangian field experiments into a mass-balance constrained food web for the Gulf of Mexico open-ocean ecosystem. This region is highly oligotrophic, yet Atlantic bluefin tuna (ABT) travel long distances from feeding grounds in the North Atlantic to spawn there. Our results show extensive nutrient regeneration fueling primary productivity (mostly by cyanobacteria and other picophytoplankton) in the upper euphotic zone. The food web is dominated by the microbial loop (>70% of net primary productivity is respired by heterotrophic bacteria and protists that feed on them). By contrast, herbivorous food web pathways from phytoplankton to metazoan zooplankton process <10% of the net primary production in the mixed layer. Nevertheless, ABT larvae feed preferentially on podonid cladocerans and other suspension-feeding zooplankton, which in turn derive much of their nutrition from nano- and micro-phytoplankton (mixotrophic flagellates, and to a lesser extent, diatoms). This allows ABT larvae to maintain a comparatively low trophic level (~4.2 for preflexion and postflexion larvae), which increases trophic transfer from phytoplankton to larval fish.

The complete mitochondrial genome of the southern calanoid copepod Calanus simillimus Giesbrecht, 1902.

The complete mitochondrial genome of Calanus simillimus is 27,876 bp in length (GenBank accession OK500294) and containing 13 protein-coding genes (PCGs), 2 rRNA genes, 22 transfer RNA genes. The gene order is novel compared to other Calanus species and copepods with sequenced mitogenomes. Phylogenetic analysis suggests that C. simillimus represent a fourth group within Calanus genus in addition to C. hyperboreus, C. finmarchicus and C. helgolandicus groups. The complete mitochondrial genome of C. simillimus will be useful for species identification, population genetics, phylogenetic and evolutionary studies among copepods.

Multigenerational study of life history traits, bioaccumulation, and molecular responses of Pseudodiaptomus annandalei to cadmium.

Metal pollution provide a substantial challenge for environmental health. This study investigated the multigeneration effects of cadmium on populations of the copepod species Pseudodiaptomus annandalei, exposed to a sublethal concentration, 40 µg/L of cadmium (Cd), over 10 generations. At the end of each generation, copepod individuals were collected to estimate fecundity, bioaccumulation, and real time qPCR quantification of selected differentially expressed genes to evaluate Cd effects and sex-specific responses of copepods across multiple generations. Our results revealed a sex-specific accumulation of Cd integrating 10 successive generations. The concentration of Cd was significantly higher (p < 0.05) in males than in females. We also observed a generational increase in Cd accumulation. Fecundity increased, with the exception of the first generation, possibly as a compensation for a decrease of copepod population size under Cd exposure. Protein expression of copepods exposed to Cd occurred in a sex-specific manner. Hemerythrin was mostly up-regulated in both copepod sexes exposed to Cd with males having the highest expression levels, while heat shock protein 70 was mostly up-regulated in males and down-regulated in female copepods, both exposed to Cd. Although copepods are known to develop adaptive mechanisms to tolerate toxic chemicals, continuous exposure to metals could lead to the bioaccumulation of metals in their offspring through maternal transfer and direct uptake from the medium over several generations. As a consequence, increased metal concentrations in copepods could result in physiological damage, reducing their fitness, and possibly compromise copepod population structures. This study showed that mortality, life history traits and molecular responses of a copepod species provided important toxicological endpoints and bio-markers for environmental risk assessments. Environmental pressure resulting from continuous exposure to persistent pollutants like Cd, could have evolutionary significance. The tendency for copepods to selectively adapt to a toxic environment through modifications, could increase their chance of survival over a long term.

Geographic Variation of Phyllodiaptomus tunguidus Mitogenomes: Genetic Differentiation and Phylogeny.

Phyllodiaptomus tunguidus (Copepoda: Calanoida) is largely endemic to and widespread in freshwater in southern China, where it inhabits a complex landscape from lowland to highland across an elevation gradient of 2000m. A deep genetic differentiation can be expected between its most distant geographic populations. Here, we sequenced nine mitogenomes from diverse populations. All mitogenomes contained 37 genes, including 13 protein-coding genes (PCG), two rRNA genes, 22 tRNA genes and one control region. Their base composition, genetic distance and tRNA structure indeed revealed a wide differentiation between mitogenomes. Two P. tunguidus from Guangxi near Vietnam differed from the other seven by up to 10.1%. Their tRNA-Arg had a complete clover-leaf structure, whereas that of the others did not contain an entire dihydrouridine arm. The nine mitogenomes also differed in the length of rRNA. NJ, ML, and Bayesian analyses all split them into two clades, viz. the two P. tunguidus from Guangxi (Clade 1), and the other seven (Clade 2). Both the structure and phylogeny of the mitogenomes suggest that P. tunguidus has complex geographic origin, and its populations in Clade 1 have long lived in isolation from those in Clade 2. They currently reach the level of subspecies or cryptic species. An extensive phylogenetic analysis of Copepoda further verified that Diaptomidae is the most recently diverging family in Calanoida and that P. tunguidus is at the evolutionary apex of the family.

Grazing behaviour of tropical calanoid copepods and its effect on phytoplankton community structure.

The Netravathi estuary is a micro- to mesotidal, tropical, shallow estuary with an abundant density of phytoplankton. The impact of the zooplankton grazing rate and the selected environmental variables on the phytoplankton community structure was studied seasonally from 2017 to 2019. Microplanktons of centric diatoms such as Skeletonema costatum and Cosinodiscus radiatus dominated during monsoon seasons, whereas dinoflagellates such as Peridinium sp. and Ceratium furca were observed in high numbers at the estuary during non-monsoon seasons. Water temperature showed a strong association with grazing rates of microzooplankton (r = 0.910). Canonical correspondence analysis studies established an intensification in grazing rate during non-monsoon seasons by calanoid copepods which in turn occasioned the reduction of microplanktons belonging to diatoms. Moreover, during monsoon seasons, diminution in grazing rates of calanoid copepods coupled with the presence of micro larvae as a secondary consumer of zooplankton resulted in the proliferation of centric diatoms. The grazing behaviour of microzooplankton affected the phytoplankton species diversity of the estuary in a negative manner (D = 0.29 in 2017 Pre-M, D = 0.76 in 2019 Pre-M). Selective grazing behaviour of calanoid copepods concerning temperature alteration exerted a strong influence in determining the phytoplankton community structure of the estuary to a great extent.

Running on empty? Freshwater feeding by spawning anadromous alewife Alosa pseudoharengus.

Anadromous alewife Alosa pseudoharengus (n = 202; mean ± s.d. fork length = 231 ± 14 mm) were captured from 10 May to 27 June 2018 in an upper watershed lake on the Isthmus of Chignecto, Canada (45°57'N, 64°14'W). Thirty individuals (mean ± s.d. fork length = 250 ± 12 mm) were captured in an adjacent estuary downstream of a tide gate on 25 April 2018. Comparing estuarine to freshwater specimens, mean gonad mass and gonadosomatic indices in males and females decreased approximately 40% and 60%, and 31% and 50%, respectively. Individuals were characterized as pre-spawners in the estuary and spawners in the lake. Males maintained similar body condition throughout the spawning run whereas female condition decreased 9.4% between the estuary and lake. Stomach fullness decreased comparing estuarine and freshwater specimens, yet 93% of stomachs examined from individuals captured in the lake contained prey. Most males fed throughout all spawning stages (3%-17% empty stomachs), while all females fed during pre- and post-spawning stages and some fasted during spawning (11% empty stomachs). Cumulative prey curve never reached an asymptote, either weekly or for the entire sampling period, so freshwater diet may not have been completely described. Calanoid copepods (79.3%IA ) were a diet staple, with the secondary prey of mayfly nymphs (O. Ephemeroptera) consumed more by females (13.6%IA ) than males (6.2%IA ). PERMANOVA and PERMDISP analyses revealed significant dietary differences in freshwater were weekly and not due to dispersion effects, thus most likely due to feeding on various development stages of insect species. Our results challenge the long-held paradigm that anadromous A. pseudoharengus fast during the spawning migration.

A new species of Pilarella (Copepoda, Calanoida, Arietellidae) from the hyperbenthic layer of Japan, with a molecular phylogenetic analysis of some representative genera of the Arietellidae.

A new species of the continental shelf hyperbenthic genus Pilarella is described, the first from the Indo-Pacific. This is the second species of Pilarella known, and the first description of a male in the genus. The new species is easily distinguished from other species of Pilarella (P. longicornis) based on: (1) short caudal rami, approximately 1.5 times longer than wide; (2) 2 setae on the mandibular endopod; (3) 6 setae on the maxillular coxal epipodite; and (4) in the female, a short left antennule reaching the posterior border of the genital double-somite. The new diagnosis of Pilarella differs from Metacalanus in the separation of ancestral segments IX-XII and XIV-XV of the antennule, and the presence of 5-6 setae on the maxillular praecoxal arthrite. Pilarella is also separated from Metacalanalis based on the absence of a seta on the third ancestral segment of the antennary exopod, the symmetry of legs 1-3, the presence of a medial basal seta on the female leg 5, and 2 lateral exopodal spines on the female leg 5. A molecular phylogenetic analysis of some representative genera of the family Arietellidae, including the present new species, recovers two arietellid clades (Metacalanus- and Arietellus-clades) as in previous studies. Dichotomous keys for the genera of Arietellidae and the species of Pilarella are included.

Proteomic fingerprinting facilitates biodiversity assessments in understudied ecosystems: A case study on integrated taxonomy of deep sea copepods.

Accurate and reliable biodiversity estimates of marine zooplankton are a prerequisite to understand how changes in diversity can affect whole ecosystems. Species identification in the deep sea is significantly impeded by high numbers of new species and decreasing numbers of taxonomic experts, hampering any assessment of biodiversity. We used in parallel morphological, genetic, and proteomic characteristics of specimens of calanoid copepods from the abyssal South Atlantic to test if proteomic fingerprinting can accelerate estimating biodiversity. We cross-validated the respective molecular discrimination methods with morphological identifications to establish COI and proteomic reference libraries, as they are a pre-requisite to assign taxonomic information to the identified molecular species clusters. Due to the high number of new species only 37% of the individuals could be assigned to species or genus level morphologically. COI sequencing was successful for 70% of the specimens analysed, while proteomic fingerprinting was successful for all specimens examined. Predicted species richness based on morphological and molecular methods was 42 morphospecies, 56 molecular operational taxonomic units (MOTUs) and 79 proteomic operational taxonomic units (POTUs), respectively. Species diversity was predicted based on proteomic profiles using hierarchical cluster analysis followed by application of the variance ratio criterion for identification of species clusters. It was comparable to species diversity calculated based on COI sequence distances. Less than 7% of specimens were misidentified by proteomic profiles when compared with COI derived MOTUs, indicating that unsupervised machine learning using solely proteomic data could be used for quickly assessing species diversity.

The genome of the European estuarine calanoid copepod Eurytemora affinis: Potential use in molecular ecotoxicology.

In this study, we sequenced and assembled the genome of a European estuarine calanoid copepod using Oxford Nanopore PromethION and Illumina HiSeq 2500 platforms. The length of the assembled genome was 776.1 Mb with N50 = 474.9 kb (BUSCO 85.9%), and the genome consisted of 2473 contigs. A total of 18,014 genes were annotated and orthologous gene clusters were analyzed in comparison to other copepods. In addition, genome-wide identification of cytochrome P450s, glutathione S-transferases, and ATP-binding cassette transporters in E. affinis was performed to determine gene repertoire of these detoxification-related gene families. Results revealed the presence of species-specific gene inventories, indicating that these gene families have evolved through species-specific gene loss/expansion processes, possibly due to adaptation to different environmental stressors. Our study provides a new inventory of the European estuarine calanoid copepod E. affinis genome with emphasis on phase I, II, and III detoxification systems.

Inter-Population Similarities and Differences in Predation Efficiency of a Mosquito Natural Enemy.

Predation is a critical factor that mediates population stability, community structure, and ecosystem function. Predatory natural enemies can contribute to the regulation of disease vector groups such as mosquitoes, particularly where they naturally co-occur across landscapes. However, we must understand inter-population variation in predatory efficiency if we are to enhance vector control. The present study thus employs a functional response (FR; resource use under different densities) approach to quantify and compare predatory interaction strengths among six populations of a predatory temporary pond specialist copepod, Lovenula raynerae, from the Eastern Cape of South Africa preying on second instar Culex pipiens complex mosquito larvae. All individuals from the sampled populations were predatory and drove significant mortality through per capita predation rates of 0.75-1.10 mosquitoes/h at maximum densities over a 5-h feeding time. Individuals from all copepod populations exhibited Type II FRs with no significant differences in attack rates. On the other hand, there were significant differences in handling times, and therefore also maximum feeding rates (maximum experimental prey density: 32), suggesting possible genetic differences among populations that influenced predation. Owing to a widespread distribution in arid landscapes, we propose that predatory calanoid copepods such as L. raynerae play a key regulatory role at the landscape scale in the control of disease vector mosquito populations. We propose that these ecosystems and their specialist biota should thus be conserved and enhanced (e.g., via selective breeding) owing to the ecosystem services they provide in the context of public health.

Factors Controlling Calanoid Copepod Biomass and Distribution in the Upper San Francisco Estuary and Implications for Managing the Imperiled Delta Smelt (Hypomesus transpacificus).

Delta smelt struggle to persist in a dramatically altered estuarine environment. Complex and incompletely understood relationships between food availability, environmental stressors, other components of the species' habitat, and the abundance of delta smelt impede the effective management and recovery of the species. The empirical modeling presented in this study quantitatively describes spatial-temporal biomass values of calanoid copepods, a key prey item for delta smelt, in relation to multiple potential controlling factors. The results underscore the role that river flows through the estuary have in determining prey availability, and demonstrate contributions of water temperature, salinity, and macronutrients in determining copepod biomass. The analysis also shows the importance of non-native, invasive bivalves in determining copepod biomass. Importantly, the analysis describes spatial-temporal shifts in the relative importance of modeled covariates across sampling locations in the Delta. Model results indicate that increasing flows in the fall of wetter years adversely affected copepod biomass, while increases in flows in the spring of drier years provided regional increases in biomass. The results of this analysis can inform resource management decisions and contribute to a comprehensive model that can meaningfully guide efforts to recover the imperiled delta smelt.

Use of scanning and image recognition technology to semi-automate larval development assessment in toxicity tests with a tropical copepod.

There is a high demand for the development of reliable chronic toxicity tests using tropical marine species for subsequent use in tropical risk assessment. However, many chronic test endpoints can be laborious and time-consuming to assess, particularly if the endpoints require measurements of individuals (e.g. growth, size) or advanced taxonomic expertise (e.g. differentiating between larval development stages). In this study, we used scanning and image recognition (SIR) technology to develop and validate a chronic toxicity test with larvae of the tropical euryhaline copepod, Acartia sinjiensis. Optimisation steps are described, and included egg age, and effect of algal food type and salinity on toxicity. Comparisons were made between traditional endpoints measured using microscopy and those measured using SIR. Traditional endpoints of larval development ratio (LDR) and survival achieved using microscope examination and SIR were almost identical (R2 = 0.96-0.97). Additional endpoints made possible by SIR included larval development index (LDI; based on the number of animals at different stages of development), and a range of size measurements (e.g. surface area, perimeter and length) for individual animals and for total populations (i.e. a proxy for biomass). The SIR-derived endpoints were based on measurements that had concentration-dependant responses to tested toxicants (copper, nickel, ammonia), and were a sub-set of the full range of metrics provided by the software. Toxicity values based on SIR-measurements were similar to or more sensitive than the traditional LDR endpoint. SIR technology provides a major opportunity to improve and modernise larval development tests for a range for species, but comes at a cost of increased data size and complexity. Therefore, as a research tool, SIR has significant advantages over traditional microscope methods, but for routine toxicity testing, SIR incorporation into invertebrate toxicity testing will benefit from further improvements to the associated software and data management systems.

The Genome and mRNA Transcriptome of the Cosmopolitan Calanoid Copepod Acartia tonsa Dana Improve the Understanding of Copepod Genome Size Evolution.

Members of the crustacean subclass Copepoda are likely the most abundant metazoans worldwide. Pelagic marine species are critical in converting planktonic microalgae to animal biomass, supporting oceanic food webs. Despite their abundance and ecological importance, only six copepod genomes are publicly available, owing to a number of factors including large genome size, repetitiveness, GC-content, and small animal size. Here, we report the seventh representative copepod genome and the first genome and the first transcriptome from the calanoid copepod species Acartia tonsa Dana, which is among the most numerous mesozooplankton in boreal coastal and estuarine waters. The ecology, physiology, and behavior of A. tonsa have been studied extensively. The genetic resources contributed in this work will allow researchers to link experimental results to molecular mechanisms. From PCR-free whole genome sequence and mRNA Illumina data, we assemble the largest copepod genome to date. We estimate that A. tonsa has a total genome size of 2.5 Gb including repetitive elements we could not resolve. The nonrepetitive fraction of the genome assembly is estimated to be 566 Mb. Our DNA sequencing-based analyses suggest there is a 14-fold difference in genome size between the six members of Copepoda with available genomic information. This finding complements nucleus staining genome size estimations, where 100-fold difference has been reported within 70 species. We briefly analyze the repeat structure in the existing copepod whole genome sequence data sets. The information presented here confirms the evolution of genome size in Copepoda and expands the scope for evolutionary inferences in Copepoda by providing several levels of genetic information from a key planktonic crustacean species.

Complete mitochondrial genome of the calanoid copepod Eurytemora affinis (Calanoida, Temoridae).

The complete mitochondrial genome was sequenced from the calanoid copepod Eurytemora affinis. The sequenced total genome size was 18,553 bp. The mitochondrial genome of E. affinis has 13 protein-coding genes (PCGs), two rRNAs, and 22 tRNAs. Of 13 PCGs, ND1, ND5, and ATP6 genes had incomplete stop codons TA-, T-, and TA-, respectively. Furthermore, the stop codons of the remaining eleven PCGs were TAG or TAA while the start codon of 13 PCGs was ATG (Cytb, ATP8, ATP6, and CO3 genes), ATT (CO1, ND2, ND3, ND4L, ND5, and ND6 genes), and ATA (ND1, ND4, and CO2 genes), respectively. The ratio of A + T and G + C nucleotides of 13 PCGs of E. affinis mitogenome showed 63.9% and 36.1%, respectively while those ratio of the entire sequences were 65.5% and 34.5%, respectively.

RNA-Seq-based transcriptome profiling and expression of 16 cytochrome P450 genes in the benzo[α]pyrene-exposed estuarine copepod Eurytemora affinis.

The calanoid copepod Eurytemora affinis is one of the most abundant estuarine species and is considered to be an ideal candidate species for ecotoxicological research. An RNA-Seq-based transcriptome was developed from whole bodies of this species. Among 142,442 contigs of the de novo assembly by Trinity, 48,480 open reading frame (ORF) contigs were found using TransDecoder. A total of 17,762 genes were identified by BLAST analysis, which covers about 75% of the annotated genes in the E. affinis genome. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that most annotated sequences were related to metabolism pathways, including xenobiotic biodegradation. Using transcriptome data, we identified putative transcripts related to xenobiotic processing genes including phase I enzymes, phase II enzymes, transporters, and transcription factors. To understand the CYP-mediated detoxification metabolism of xenobiotics, we measured the transcriptional levels of 16 CYPs (within full sequences) of E. affinis in response to benzo[α]pyrene (B[α]P). Most Ea-CYP genes were significantly down- and/or up-regulated (P < 0.05) in response to B[α]P, suggesting that Ea-CYP genes are likely involved in detoxification (mainly in biotransformation of xenobiotics) with particular genes, demonstrating significant upregulation or downregulation compared to others, as shown in other copepod model species (e.g. Tigriopus japonicus and Paracyclopina nana). This study will provide insight into the potential role of E. affinis in response to various toxic or xenobiotic chemicals in the marine environment.