Female Copepods Research Articles

Comparative assessment of microplastics and microalgae as vectors of mercury and chlorpyrifos in the copepod Acartia tonsa

Microplastics (MPs) raise concerns not only as pollutants themselves, but also due to their ability to act as vectors of pollutants adsorbed from seawater, transferring them to marine organisms. However, the relevance of MPs as carriers of pollutants compared to microalgae needs further exploration. This study compared the role of MPs (2–10 μm non-oxidized and 10–15 μm oxidized high-density polyethylene) and natural organic particles (Rhodomonas lens microalgae, MA) as carriers of mercury (Hg, 2.3 μg Hg/L) and chlorpyrifos (CPF, 1.0 μg CPF/L) to adult Acartia tonsa copepods, after 24–48 h exposure. Dose-response experiments were first performed with adult female copepods exposed to oxidized MPs (0.25–4.0 mg/L), waterborne Hg (0.01–10.0 μg/L) and Ox MPs + Hg (0.25–4.0 mg oxidized MPs/L + 0.50–8.0 μg Hg/L) for 48 h, to complement previous studies that focused on the pesticide CPF. Effects were evaluated with four replicates for physiological and reproductive responses (6 females/replicate), biochemical techniques (40 individuals/replicate) and Hg/CPF bioaccumulation measurements (1000 individuals/replicate). Copepods accumulated Hg/CPF similarly from dissolved pollutants (6204 ± 2265 ng Hg/g and 1251 ± 646 ng CPF/g) and loaded MPs (3125 ± 1389 ng Hg/g and 1156 ± 266 ng CPF/g), but significantly less from loaded MA (21 ± 8 ng Hg/g and 173 ± 80 ng CPF/g). After 24–48 h, copepods exposed to MPs + Hg/CPF showed generally greater biological effects than those exposed to dissolved Hg/CPF or to MA + Hg/CPF, although differences were not statistically significant. MA + CPF had significantly lower AChE inhibition (1073.4 nmol min−1 mg−1) and MA + Hg lower GRx induction (48.8 nmol min−1 mg−1) compared to MPs + Hg/CPF and dissolved Hg/CPF (182.8–236.4 nmol min−1 mg−1 of AChE and 74.1–101.7 nmol min−1 mg−1 of GRx). Principal component analysis suggested different modes of action for Hg and CPF.

Evidence for infection influencing survival of the freshwater copepod Salmincola californiensis, a parasite of Pacific salmon and trout.

We explore apparent infection of Salmincola californiensis arising during investigations involving this lernaeopodid copepod parasitic on Pacific salmon and trout Oncorhynchus spp. We noted occasional unusual coloration of adult female copepods collected from the wild. These females were bright blue and pink in contrast to the cream white coloration characteristic of the copepod. We also observed that similar color patterns developed under laboratory settings when copepod eggs were held for hatching. In paired egg cases, we found consistent hatching failure of blue and pink eggs and patterns in apparent disease development that would be consistent with both vertical and horizontal transmission. Attempts to identify the cause of the apparent infection using genetic methods and transmission electron microscopy were inconclusive. Iridovirus infection was initially suspected, but bacterial infection is also plausible. This apparent reduced hatching success of S. californiensis warrants further exploration as it could reduce local abundances. Given the potential importance of a disease impacting this copepod, a parasite that itself affects endangered and commercially important Pacific salmon and trout, future research would benefit from clarification of the apparent infection through additional sequencing, primer development, visualization, and exploration into specificity and transmission.

First Report of Caligus minimus Otto, 1821 (Copepoda: Siphonostomatoida: Caligidae) from Plankton Samples Collected from Türkiye

During a plankton sampling conducted off the northeastern Mediterranean coast of Türkiye, a single female copepod, Caligus minimus Otto, 1821 was collected from a marine plankton sample. C. minimus is a well-known species of the genus Caligus O.F. Müller, 1785 which has been previously reported as a parasite from nine marine fish species belonging to eight different families. To date, however, C. minimus has never been reported from plankton samples. In this study, the general morphology based on the key diagnostic characters of the planktonic C. minimus is presented using confocal laser scanning microscope (CLSM) images. This is the first report of C. minimus from plankton samples off Turkish waters and global marine environments.

Reduced Survival and Disruption of Female Reproductive Output in Two Copepod Species (Acartia clausi and A. tonsa) Exposed to the Model Endocrine Disruptor 17α-Ethinylestradiol.

Estuaries are heavily impacted by pollutants from different sources such as urban sewage, industrial waste and agricultural runoff. Endocrine-disrupting chemicals (EDCs) are very concerning pollutants to estuarine wildlife, but little is known about their impact on microscopic biota such as zooplankton. The aim of this work was to investigate the effects of a model EDC, the 17α-ethinylestradiol (EE2), on two copepod species inhabiting the Basque coast (Southeastern Bay of Biscay) estuaries: Acartia clausi (autochthonous neritic species) and Acartia tonsa (non-indigenous brackish species). Female copepods were collected at population maximum time (spring for A. clausi and summer for A. tonsa) and exposed individually to 5 ng/L (low), 5 µg/L (medium) and 500 µg/L EE2 (high) doses, from environmental concentrations found in sewage effluents to toxicological concentrations. After 24 h exposure, the survival rate of experimental individuals was checked and the lethal concentration LC50 was calculated. The number of egg-producing females and the amount of egg laying and egg hatching were recorded. The integrated biomarker index (IBR) was calculated to integrate the overall effects of EE2 exposure. Both species had reduced survival rates at 500 µg/L, and the LC50 was lower in A. tonsa (158 µg/L) compared to A. clausi (398 µg/L). The number of eggs laid was significantly reduced in A. clausi at EE2 medium and high doses, while a reduction in the number of eggs in A. tonsa was observed only at the high dose. However, no significant differences were detected in the egg hatching success of exposed A. clausi and A. tonsa. IBR index showed that EE2 had the most detrimental effects on A. tonsa and A. clausi females at the 500 µg/L dose. In conclusion, after 24 h of exposure, EE2 reduced female copepod survival and disrupted reproductive output, but only at high non-environmentally relevant concentrations.

The Infection of Paracalanid Copepods by the Alveolate Parasite Ellobiopsis chattoni Caullery, 1910 in a Subtropical Coastal Area

Paracalanid copepods, common in tropical zooplankton communities, are known hosts for a variety of parasites. Nevertheless, relatively little is known about the prevalence and consequences of parasitism in these copepods. In this study, we analyzed the relationship between two paracalanid copepods, Parvocalanus crassirostris and Paracalanus spp., with a common parasite, the alveolate protist Ellobiopsis chattoni, in a subtropical environment on the south-east Brazilian coast. We assessed the frequency and abundance of parasites in juveniles and adult male and female copepods. We observed that 22 out of 4014 Paracalanus spp. (0.55%) and 98 out of 3920 P. crassirostris were infected (2.5%). E. chattoni were rarely found in other taxa (about 0.05% for Oithona spp. and Acartia lilljeborgii). The parasites were most frequently attached to cephalosome appendages (73.6%), with up to four cells per copepod. The parasites were more prevalent in adults than juveniles, and adult females were more frequently infected than males. E. chattoni had a likely negative impact on copepod growth because the infected females were smaller than the non-infected females (p < 0.001). Females are usually bigger and live longer than males, which could account for their high frequency of infection.

Mitochondria directly boost copepods’ rosy hue

In the search for the ideal mate, many creatures keep an eye out for the brightest and best. ‘The colourful displays of an animal often tell us how strong, successful and healthy that animal is’, says Matthew Powers from Auburn University, USA. But for an animal to truthfully convey its inner strength through beauty, there must be a direct link between an attractive characteristic and their physiological prowess: enter the mitochondrial power houses of the cell. These minute organelles, tucked away inside almost every animal cell, consume glucose and oxygen to generate most of the chemical energy that powers life. The power structures also produce the ideal environment for converting colourful yellow pigments (carotenoids, consumed by creatures in their diets) into redder shades, which could trumpet the honest truth about an animal's suitability as a mate. But proving the direct link between the cellular power sources and a creature's attractiveness is tricky, because mitochondria also produce toxins that could blanch vibrant hues, diminishing the message. However, Powers and Geoffrey Hill, from Auburn University, knew of an alternative strategy, which could speed up the mitochondria, affecting an animal's hue in turn if the two were linked, so they focused their attention on a tiny rose-coloured copepod, Tigriopus californicus.The minute crustaceans dine on algae containing yellow carotenoids, which they then convert into the red keratinoid astaxanthin, so Powers, Alex Baty (Auburn University) and Hill bathed the miniature crustaceans in a drug known as DNP, which increases the mitochondria's oxygen consumption. If the copepods’ colour and the powerfulness of their mitochondria were linked directly, then increasing the organelles’ oxygen consumption could, in turn, speed up conversion of the yellow pigment into the more vivid astaxanthin, resulting in redder copepods.After collecting the tiny crustaceans after a week of bathing in the mitochondrial energising drug, Powers and Baty discovered that the male copepods were producing 70% more red astaxanthin than the copepods that did not receive the mitochondrial boosting drug. And, when the duo took transparent copepods that had been raised on colourless yeast for the whole of their lives and switched their diet to the colour-creating plankton, the female copepods that received a DNP boost produced 23% more astaxanthin than the copepods fed on the plankton alone. The team also measured how much oxygen individual copepods consumed, an indication of how active their mitochondria are, and compared that with the animals’ astaxanthin levels, discovering that the crustaceans with the most power-hungry mitochondria were also the reddest, directly linking the copepods’ mitochondrial power to their rosy hue. ‘These data support Hill's hypothesis that ketocarotenoid and mitochondrial metabolism are biochemically intertwined’, says Powers.But why do T. californicus go to such vivid lengths if they are not trying to make their appearance as alluring as possible? After all, copepods are immune to the appeal of their mates’ lustrous tint. Powers and colleagues explain that the red pigment behaves effectively as sunscreen, shading the animal from damaging UV rays. Instead of communicating their suitability as a mate, the crustaceans are simply benefiting from the protective properties of a side effect of their powerful energy-generating mitochondria.

Physiological and molecular responses of the Antarctic harpacticoid copepod Tigriopus kingsejongensis to salinity fluctuations - A multigenerational study.

Since Antarctica and the surrounding Southern Ocean are facing global climate change, biota inhabiting those coastal regions is now challenged by environmental fluctuations including coastal freshening. In this study, the effects of salinity range of 0-75 (practical salinity unit, PSU) on the Antarctic harpacticoid copepod Tigriopus kingsejongensis was investigated by measurement of 96h survival rate, lifespan, and sex ratio with further analysis of multigenerational growth parameters and mRNA expressions under salinity of 15-45. Different stages of the copepods (i.e., nauplius, male, and female) generally showed tolerance to hypo- and hypersalinity, wherein female copepods were more tolerant than males when exposed to salinity fluctuations. Lifespan was significantly shortened by hypo- and hypersalinity compared to control salinity (34), but there was no significant difference in the sex ratio between salinity treatments. Multigenerational experiments across five generations revealed that exposure to salinities of 15 and 45 reduced body length compared to that in control salinity and the first generation of each salinity group. Our results provide evidence regarding T. kingsejongensis on their preferred salinity ranges, physiological limit to salinity fluctuations, and population dynamics in future salinity.

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.

Host-parasite Interactions between a Copepod (Pharodes tortugensis) and Small Reef-associated Gobies (Coryphopterus) in the British Virgin Islands.

The effects of parasitic copepods on free-living hosts are infrequently documented, and the copepod Pharodes tortugensis has remained virtually unstudied since described. For the first time, we document its host range in the British Virgin Islands (BVI), the prevalence and intensity of infections on wild hosts, and its impacts on host morphology and performance. Infections were observed on four benthic gobies in the BVI (Coryphopterus glaucofraenum, C. venezuelae, C. dicrus and C. eidolon) but not on other host species previously reported from other parts of the western Atlantic. Infected gobies were widespread in the BVI (detected at 33 of 52 sites, prevalence from 1-25%) but extremely rare elsewhere in the Caribbean (detected at 2 of 16 sites, prevalence < 0.006%). As is typical of macroparasite infections, P. tortugensis was over-dispersed in BVI host populations (mean intensity = 4.7, range = 1-17). Infections were most common in juvenile and female hosts, and rarely found in larger male hosts. The copepods attach in the branchial chamber of the goby; female copepods show high attachment fidelity to the ventral surface of the chamber, while male copepods attached most often to the first two gill arches and in the branchial chamber adjacent to the female. Infections caused substantial damage to the host's branchial chamber and gill filaments. Parasitized gobies also had larger livers and smaller gonads than unparasitized individuals of similar length. The changes in organ mass of infected gobies were not sizeable enough to affect total body mass, and host condition (the body-length vs. body-mass relationship) was similar for gobies with and without infections. Parasitized gobies were, however, significantly smaller in body mass at a given age, reflecting slower overall growth. Effects of P. tortugensis on individual hosts were broadly similar to those of other parasitic copepods that infect fish gills and, for unknown reasons, the BVI appears to be a persistent hotspot of infections on these goby hosts.

Reproductive trade-offs of the estuarine copepod Eurytemora affinis under different thermal and haline regimes

Copepod females invest a quantity of resources in their reproduction. Depending on several biotic and abiotic factors and their evolutionary history a trade-off can be commonly observed between producing a large number of smaller offspring or a small number of larger offspring. In this study, a multi-generational approach was applied to determine whether a trade-off between clutch size and egg size existed in the copepod Eurytemora affinis under different controlled conditions of temperature and salinity. This protocol was based on the follow-up of reproductive (Clutch Size ‘CS’, Egg Diameter ‘ED’) and morphological (Prosome Length ‘PL’) traits during several generations. Copepods were acclimated to cold (7 °C) and warm (20 °C) temperatures, and then their reproductive output was tested at the higher temperature of 24 °C. CS and ED were positively correlated to PL, so as a first step linear regressions between each reproductive trait and female PL were performed. The residuals from the regression lines of CS and ED with PL were calculated to remove the effect of female size. When the normalized data (residuals) of CS and ED plotted together a negative relationship between egg size and egg number revealed the existence of a trade-off. Copepod populations initially acclimated to cold temperature are commonly characterized by relatively smaller CS and larger ED. Conversely, warm temperature adapted females produced relatively larger CS and smaller ED. After transfer to a temperature of 24 °C, the ED did not change but the CS showed high variability indicating stressful conditions and no trade-off was observed. These observations suggest that E. affinis is able to modulate its reproduction depending on the encountered temperature. It seems that this copepod species can shift between a K- and an r-strategy in response to colder or warmer conditions. In a late winter-early spring like cold temperature, copepod females seem to invest more on offspring quality by producing relatively larger eggs. This ecological strategy ensures a high recruitment of the spring generation that is responsible for the strength of the maximum population size usually observed in late spring-early summer (May–June). To the contrary, at summer-like temperature, where the population density decreases significantly in the Seine estuary, copepod females seem to switch from K to r strategy by favoring offspring number compared to offspring size. Finally, the use of a higher temperature of 24 °C seems to disrupt the observed reproductive trade-off even after several generations. These results suggest that a switching between K- or r-strategy of E. affinis depends highly on temperature effects. The effect of salinity increase during a summer-like temperature of 20 °C as well as after transfer to 24 °C decreased PL and CS but the ED did not change significantly.

Promotion of the Development of Sentinel Species in the Water Column: Example Using Body Size and Fecundity of the Egg-Bearing Calanoid Copepod Eurytemora affinis

The development of sentinel species in aquatic ecosystems is mostly based on benthic organisms; however, organisms living in water column such as zooplankton have received less attention, except for some cladocerans. In this paper, a new ecological indicator based on simple measurements of the size and fecundity of egg-bearing calanoid copepods is developed. The well-studied estuarine copepod Eurytemora affinis is used to illustrate this new framework. A large database obtained from laboratory experiments developed under different conditions is used to define a reference regression line between clutch size (CS) and prosome length (PL). The same database allowed one to confirm that the coefficient of variation (CV) of CS is an adequate estimator of the accumulated stress at population level. The CV of PL shows very little variability in all experimental and field conditions. The values of CS and PL obtained from the Seine, Loire, Gironde, Scheldt and Elbe estuaries in Europe are compared to the reference regression line. A quality index (QI) is calculated as a percentage of difference between the observed and the predicted CS. The QI classified 19 samples collected in the Seine estuary between 2004 and 2010 into four classes according to the physiological condition of the copepod female. A single sampling from June 2004 (5.26%) showed a very good condition, whereas 57.9% of the sampling dates confirmed good conditions. On the other hand, four sampling dates were associated to very bad conditions and three sampling dates indicated bad conditions. Seven additional samples obtained from other European estuaries between 2006 and 2009 were also used. Females showing poor conditions were observed in the early spring of 2005 and 2008 as well as during the month of November. These years were characterized by very strong climatic anomalies with a very cold late winter in 2005 and a warm winter in 2008. Therefore, it seems that the QI perfectly reflected the strong stress caused by the sudden change in hydro-climatic conditions that have certainly affected the physiology of copepod females and probably the availability of food. The new indicator is very simple to calculate and can be generalised to several aquatic ecosystems (fresh water and brackish water) by targeting the dominating egg-bearing calanoid copepods. As in the case of E. affinis, the development of sentinel species based on copepods or cladocerans can enrich ecological and ecotoxicological studies given their capacity to integrate the variability of their habitats’ quality at the individual and population levels.

RNA-Seq and differential gene expression analysis in Temora stylifera copepod females with contrasting non-feeding nauplii survival rates: an environmental transcriptomics study

BackgroundCopepods are fundamental components of pelagic food webs, but reports on how molecular responses link to reproductive success in natural populations are still scarce. We present a de novo transcriptome assembly and differential expression (DE) analysis in Temora stylifera females collected in the Gulf of Naples, Mediterranean Sea, where this copepod dominates the zooplankton community. High-Throughput RNA-Sequencing and DE analysis were performed from adult females collected on consecutive weeks (May 23rd and 30th 2017), because opposite naupliar survival rates were observed. We aimed at detecting key genes that may have influenced copepod reproductive potential in natural populations and whose expression was potentially affected by phytoplankton-derived oxylipins, lipoxygenase-derived products strongly impacting copepod naupliar survival.ResultsOn the two sampling dates, temperature, salinity, pH and oxygen remained stable, while variations in phytoplankton cell concentration, oxylipin concentration and oxylipin-per-diatom-cell production were observed. T. stylifera naupliar survival was 25% on May 23rd and 93% on May 30th. De novo assembly generated 268,665 transcripts (isoforms) and 120,749 unique ‘Trinity predicted genes’ (unigenes), of which 50% were functionally annotated. Out of the 331 transcript isoforms differentially expressed between the two sampling dates, 119 sequences were functionally annotated (58 up- and 61 down-regulated). Among predicted genes (unigenes), 144 sequences were differentially expressed and 31 (6 up-regulated and 25 down-regulated) were functionally annotated. Most of the significantly down-regulated unigenes and isoforms were A5 Putative Odorant Binding Protein (Obp). Other differentially expressed sequences (isoforms and unigenes) related to developmental metabolic processes, protein ubiquitination, response to stress, oxidation-reduction reactions and hydrolase activities. DE analysis was validated through Real Time-quantitative PCR of 9 unigenes and 3 isoforms.ConclusionsDifferential expression of sequences involved in signal detection and transduction, cell differentiation and development offered a functional interpretation to the maternally-mediated low naupliar survival rates observed in samples collected on May 23rd. Down-regulation of A5 Obp along with higher quantities of oxylipins-per-litre and oxylipins-per-diatom-cell observed on May 23rd could suggest oxylipin-mediated impairment of naupliar survival in natural populations of T. stylifera. Our results may help identify biomarker genes explaining variations in copepod reproductive responses at a molecular level.

Differential gene expression profile of male and female copepods in response to cadmium exposure

In this study, the whole transcriptome and sex-specific differential gene expression of the copepod Pseudodiaptomus annandalei exposed to cadmium (Cd) were investigated. P. annandalei were exposed to 40 μg/L Cd from the naupliar stage to male and female adults. High-throughput transcriptome sequencing (RNA-seq) was performed with copepod samples using an Illumina Hiseq™ 2000 platform. TransDecoder analysis found 32,625 putative open reading frame contigs. At p-values of <0.001, a total of 4756 differentially expressed genes (DEGs) (2216 up-regulated and 2540 down-regulated genes) were found in male copepods. Whereas a total of 2879 DEGs (2007 up-regulated and 872 down-regulated genes) were found in female copepods. A few selected cellular stress response genes, involved in xenobiotic metabolism, energy metabolism, growth, and development as a result of Cd exposure in the copepods were discussed. The study showed that most of these processes were changed in a sex-specific manner, accounting for the different sensitivities of male and female copepods. Results suggest and reinforce that sex is an important factor to be considered in ecotoxicogenomics.

Are egg production and respiration of the marine pelagic copepod Acartia steueri influenced by crowding?

The understanding of the biological responses of copepods under crowding conditions contributes to establish their stable cultures at high densities for aquaculture industry, which are preferred live feeds for fish larvae. The present study investigated survivorship, fecundity, hatching success and respiration rate, of Acartia steueri raised under five densities, from 100 to 2,000 ind. L−1, to clarify the biological responses of the copepod under dense culture. There were no significant differences in survival, fecundity and hatching success among all density conditions, whereas the respiration rate at 2,000 ind. L−1 decreased by 80% as compared with a condition at 100 ind. L−1. The female copepods raised under a copepod density of >500 ind. L−1 probably invested a larger proportion of energy in reproduction in relation to total assimilated energy as compared with females under lower copepod densities. This change of energy allocation may allow A. steueri under high densities to maintain high fecundity. Acartia steueri might be a promising species for dense culture because its mortality and fecundity were independent of the effect of crowding, and the density-dependent reduction in the metabolic rate might increase reproductive investment to maintain a constant rate of reproduction even under high densities.

Продукционные характеристики копепод Arctodiaptomus salinus и Calanipeda aquaedulcis при питании смесью микроводорослей Dinophyceae и Prymnesiophyceae

Убиквитные виды копепод Arctodiaptomus salinus (Daday, 1885) и Calanipeda aquaedulcis (Krichagin, 1873) — важные компоненты пищевых цепей многочисленных пресных и солёных водоёмов. Данные копеподы пригодны для кормления личинок как морских, так и пресноводных видов рыб, однако влияние питания на продукционные характеристики этих видов копепод изучено недостаточно. Ранее нами было определено, что монокультуры микроводорослей Dinophyceae и Prymnesiophyceae являются оптимальными кормовыми объектами для продуцирования яиц самками A. salinus и C. aquaedulcis, выживаемости и скорости развития этих копепод на всём протяжении их онтогенеза. Цель данной работы заключалась в определении продукционных характеристик копепод A. salinus и C. aquaedulcis в оптимальных температурных условиях в зависимости от варианта питания смесью микроводорослей Dinophyceae и Prymnesiophyceae. Наиболее высокие значения выживаемости A. salinus от науплиальной до взрослой стадии развития (93–95 %) отмечены при питании копепод монокультурой микроводоросли Isochrysis galbana (Parke, 1949) и смесью I. galbana + Prorocentrum cordatum (Ostenfeld) J. D. Dodge, 1975; наименьшая продолжительность развития (19 суток) — при кормлении смесью из трёх микроводорослей I. galbana + P. cordatum + Prorocentrum micans (Ehrenberg, 1834). Наименьшая средняя продолжительность развития C. aquaedulcis от науплиальной до взрослой стадии развития (13 сут.) зафиксирована при питании смесью микроводорослей I. galbana + P. cordatum. Наименьшая продолжительность науплиального периода развития копепод обоих видов отмечена тогда, когда в состав их диеты входила I. galbana в качестве моно- или одного из компонентов смеси. Такая же закономерность сохраняется для копеподитного периода, только уже с P. cordatum. Максимальная абсолютная плодовитость C. aquaedulcis достигала 24 яиц на самку (I. galbana), A. salinus — 16 яиц на самку (P. cordatum). Выклев C. aquaedulcis при питании как монокультурами микроводорослей P. cordatum и I. galbana, так и их смесью достигал 100 %. Для A. salinus только питание самок смесью микроводорослей I. galbana + P. micans обуславливает максимальный процент выклева.

Lipid storage patterns in marine copepods: environmental, ecological, and intrinsic drivers

Abstract Seasonality of food supply is a major driver of physiological and ecological adaptations of marine zooplankton. High-latitude marine copepods accumulate lipids for maintenance and reproductive maturation during the food-depleted winter period. The relationship between latitude and lipid storage in copepods is well established, but it is influenced by many factors, such as trophic position, sex, and depth distribution. In this study, the influence of latitude and collection depth, trophic level, sex, and the presence or absence of dormancy on the relative amount and composition of lipids stored was assessed by analysing published data. Our analyses confirmed higher lipid contents (expressed as % dry weight) in high-latitude species, and in deep-dwelling tropical copepods compared to shallow-living ones. Contrary to our original hypothesis, carnivorous and herbivorous copepods had similar lipid levels. Copepod species that undergo dormancy had higher levels of wax ester and were more common at polar and temperate latitudes. Lastly, adult male and female copepods did not significantly differ in the amount of lipids they store, suggesting that the portion of male reproductive investment, which may depend on lipid stores, has been underestimated. Taken together, these results both confirm some previously reported trends and refute others.

Effects of maternal phosphorus deficiency on reproductive allocation of the copepod Pseudodiaptomus annandalei Sewell, 1919

The nutrient status of phytoplankton affects the reproductive traits of zooplankton, yet no study has addressed how reproductive allocation varies with phosphorus (P) availability in copepods. We hypothesized that maternal P deficiency reduces reproductive investment in copepods and that interactions exist between maternal and postnatal P condition effects on offspring development. Females of the copepod Pseudodiaptomus annandalei were fed algal prey with different P contents, then allocation of elements and fatty acids in offspring and naupliar development of offspring were measured. Females reduced total reproductive efforts and P investment per offspring under P-deficient conditions. Gross reproduction efficiency of P and the proportion of available maternal P invested in reproduction increased as P consumption decreased, revealing priority of reproductive investment under P deficiency. A high proportion of body docosahexaenoic acid was allocated into reproduction, regardless of the dietary P condition. Duration of naupliar phase and body length at stage CI in offspring were independent of the initial maternal P investment, implying a low P demand for early copepod development. As such, female copepods may down-regulate P investment per offspring to offset impairment of P deficiency on their fitness, and to maximize number of offspring at a given level of P availability.

Examining intraspecific multiple predator effects across shifting predator sex ratios

Predator-predator interactions, or “multiple predator effects” (MPEs), are pervasive in the structuring of communities and complicate predictive quantifications of ecosystem dynamics. The nature of MPEs is also context-dependent, manifesting differently among species, prey densities and habitat structures. However, there has hitherto been a lack of consideration for the implications of intraspecific demographic variation within populations for the strength of MPEs. The present study extends MPE concepts to examine intraspecific interactions among male and female predators across differences in prey densities using a functional response approach. Focusing on a copepod-mosquito model predator-prey system, interaction strengths of different sex ratio pairs of Lovenula raynerae were quantified towards larval Culex pipiens complex prey, with observations compared to both additive and substitutive model predictions. Copepods exhibited destabilising Type II functional responses in all treatments, with female copepods significantly more voracious than males under multiple predator groups. Lovenula raynerae exhibited significantly negative MPEs overall which resulted in prey risk reductions. However, whilst not statistically clear, the magnitude of antagonistic interactions subtly differed among predator-predator compositions and prey densities, with female-female antagonisms generally prevalent at low prey densities, and male-male negative interactions greater under high prey densities. Mixed-sex copepod group predation was predicted by both additive and substitutive models, and additive models generated significantly higher consumption estimates than substitutive equivalents given that their predictions were based on the absence of antagonistic non-trophic interactions. We propose the importance of internal population sex demographics as a further context-dependency which influences the nature of MPEs, with demographic implications requiring investigation across other taxonomic and trophic groups.

Metabarcoding analysis of regional variation in gut contents of the copepod Calanus finmarchicus in the North Atlantic Ocean

The calanoid copepod Calanus finmarchicus is one of the most abundant and ecologically important species of the zooplankton assemblage of the North Atlantic Ocean and occupies a pivotal position in the pelagic food web. This study used metabarcoding analysis (high throughput DNA sequencing of target gene regions) to examine the diversity of the copepod gut content, including both eukaryotic and prokaryotic components of the diet and microbiome. Zooplankton samples were collected during the 2013 EuroBASIN cruise of the R/V G.O. Sars, which crossed the North Atlantic to survey in the Norwegian, Icelandic, Irminger, and Labrador Seas. Zooplankton samples were examined microscopically for C. finmarchicus; species identification was confirmed by genetic markers based on insertion-deletion sequence variation. DNA was extracted from the dissected gut contents of adult female copepods and sequenced for eukaryotic 18S V4 and prokaryotic 16S V3–V4 rRNA hypervariable regions. Prokaryotes identified in the gut contents of all copepods analyzed included Cyanobacteria, Proteobacteria, Bacteroidetes, Planctomycetes, Actinobacteria, and Acidobacteria. The eukaryotic gut content assemblage was diverse, dominated by Ocrophyta (diatoms), Dinophyta (dinoflagellates), Ciliophora (ciliates), as well as Cnidaria and Ctenophora. The diverse assemblage revealed by metabarcoding analysis of copepod gut contents likely represents prey, microbiome, parasites, symbionts, and pathogens. Significant differences in prokaryotic and eukaryotic diversity of the gut contents of copepods collected from four regional seas of the North Atlantic Ocean reflect and contribute to basin-scale differences in the pelagic food web of these ecosystems. This study provides evidence that diversity and variation of the copepod gut contents may both reflect and impact the functioning of pelagic food webs and regional variation in ocean ecosystems.

Sex demographics alter the effect of habitat structure on predation by a temporary pond specialist

Habitat structure can profoundly influence interaction strengths between predators and prey. Spatio-temporal habitat structure in temporary wetland ecosystems is particularly variable because of fluctuations in water levels and vegetation colonisation dynamics. Demographic characteristics within animal populations may also alter the influence of habitat structure on biotic interactions, but have remained untested. Here, we investigate the influence of vegetation habitat structure on the consumption of larval mosquito prey by the calanoid copepod Lovenula raynerae, a temporary pond specialist. Increased habitat complexity reduced predation, and gravid female copepods were generally more voracious than male copepods in simplified habitats. However, sexes were more similar as habitat complexity increased. Type II functional responses were exhibited by the copepods irrespective of habitat complexity and sex, owing to consistent high prey acquisition at low prey densities. Attack rates by copepods were relatively unaffected by the complexity gradient, whilst handling times lengthened under more complex environments in gravid female copepods. We demonstrate emergent effects of habitat complexity across species demographics, with predation by males more robust to differences in habitat complexity than females. For ecosystems such as temporary ponds where sex-skewed predator ratios develop, our laboratory findings suggest habitat complexity and sex demographics mediate prey risk.