Pelagic Copepods Research Articles

Population dynamics of Pseudocalanus minutus elongatus in the Gulf of Gdansk (southern Baltic Sea) – experimental and numerical results

The seasonal and spatial distribution of the pelagic calanoid copepod Pseudocalanus minutus elongatus was studied in the Gulf of Gdansk (southern Baltic Sea) between January 2006 and December 2007 based on experimental data (from six stations) and numerical simulations. Numerical calculations were performed using a structured zooplankton population model that was adapted to this species and coupled to the ecosystem model. Spatiotemporal distribution of this species depends on salinity as a masking factor. Highest abundances at station J23, an open sea site, were observed in July 2006 and March 2007 (10,050 and 11,000 ind. m−3, respectively) and resulted from the large numbers of earlier copepodites C1–C3 in 2006 and nauplii in 2007. In shallow stations abundances declined. Our results show that only one complete generation of this copepod species developed during the year in this region. Differences in development between the experimental and numerical data are analysed.

Notes on feeding ecology of macrourid fishes from the mid-Atlantic Ridge, North Atlantic

At least 16 macrourid fishes (Gadiformes, Macrouridae) inhabit the mid-Atlantic Ridge of the North Atlantic. To investigate the roles of macrourids in the food-web and compare feeding patterns of the most frequent co-occurring species, diet information on five of the species were described and compared. Pelagic and benthopelagic copepods were the most numerous prey but did not contribute much on a weight basis. Cephalopods were by far the most important prey of the small grenadiers, while shrimps and fish became increasingly significant with increasing size. Previous studies from other areas have also found pelagic prey to be important, but in contrast to this study, cephalopods were more important on the mid-Atlantic Ridge than in continental margin locations.

Optimal mate choice patterns in pelagic copepods

The importance of sexual selection for the evolution, dynamics and adaptation of organisms is well known for many species. However, the topic is rarely studied in marine plankton, the basis of the marine food web. Copepods show behaviors that suggest the existence of sexually selected traits, and recent laboratory experiments identified some selected morphological traits. Here, we use a 'life history-based' model of sex roles to determine the optimal choosiness behavior of male and female copepods for important copepod traits. Copepod females are predicted to be choosy at population densities typically occurring during the main breeding season, whereas males are not. The main drivers of this pattern are population density and the difference in non-receptive periods between males and females. This suggests that male reproductive traits have evolved mainly due to mate competition. The model can easily be parameterized for other planktonic organisms, and be used to plan experiments about sexual selection.

The Kinematics of Swimming and Relocation Jumps in Copepod Nauplii

Copepod nauplii move in a world dominated by viscosity. Their swimming-by-jumping propulsion mode, with alternating power and recovery strokes of three pairs of cephalic appendages, is fundamentally different from the way other microplankters move. Protozoans move using cilia or flagella, and copepodites are equipped with highly specialized swimming legs. In some species the nauplius may also propel itself more slowly through the water by beating and rotating the appendages in a different, more complex pattern. We use high-speed video to describe jumping and swimming in nauplii of three species of pelagic copepods: Temora longicornis, Oithona davisae and Acartia tonsa. The kinematics of jumping is similar between the three species. Jumps result in a very erratic translation with no phase of passive coasting and the nauplii move backwards during recovery strokes. This is due to poorly synchronized recovery strokes and a low beat frequency relative to the coasting time scale. For the same reason, the propulsion efficiency of the nauplii is low. Given the universality of the nauplius body plan, it is surprising that they seem to be inefficient when jumping, which is different from the very efficient larger copepodites. A slow-swimming mode is only displayed by T. longicornis. In this mode, beating of the appendages results in the creation of a strong feeding current that is about 10 times faster than the average translation speed of the nauplius. The nauplius is thus essentially hovering when feeding, which results in a higher feeding efficiency than that of a nauplius cruising through the water.

Distribution patterns of appendicularians and copepods and their relationship on the northwest continental shelf of South China Sea during summer

The potential suppression of copepods on appendicularians was found in field and experimental conditions. The abundance and distribution of appendicularians and planktonic copepods were studied with reference to their correlations during summer on the northwest continental shelf of the South China Sea (SCS). Based on the topography and water mass of the surveyed region, it was divided into three sub-regions: Region I (inshore waters of the east Leizhou Peninsula) with low temperature, salinity and high chlorophyll a (Chl a) concentration, Region II (inshore waters of the east and southeast Hainan Island) with low temperature, high salinity and moderate Chl a concentration and Region III (offshore waters from the Leizhou Peninsula to Hainan Island) with high temperature, high salinity and low Chl a concentration. The species richness of appendicularians and copepods increased from the inshore to offshore waters, and high values were observed in Region III. The distribution of appendicularian and copepod abundance decreased generally from the inshore to offshore waters, with the highest values at Region I. Our results suggest that the distribution patterns of appendicularians and copepods differed significantly, as a result of the influence of physical and biological factors. The negative impact of pelagic copepods on appendicularians was not found based on in situ data in the northwest continental shelf of SCS.

The smell of virgins: mating status of females affects male swimming behaviour in Oithona davisae

Many copepod species rely on pheromone cues to find partners. Some parasitic and benthic copepod males are able to distinguish between females of different reproductive states. Here, we demonstrate that the swimming activity and velocity of males of a pelagic copepod, Oithona davisae, increases in the presence of virgin when compared with mated females and that the cue is waterborne. The ability to distinguish between virgin and mated females may reduce male mortality during mate search and the cost related to mating behaviour (precopula) in both sexes. We estimate that at realistic population densities the ability of males to distinguish between virgin and mated females saves them several hours per day of dangerous and energetically expensive fast female tracking.

The mechanisms leading to ontogenetic diet shift in a microcanivore, Pterogobius elapoides (Gobiidae)

A variety of fish species undergo an ontogenetic change in prey selectivity, and several potentially interacting factors, including nutrient requirement, microhabitat change, and foraging ability, may account for the occurrence of the shift. Here we examine the foraging ecology and ontogenetic diet shift of a micro-carnivorous goby, Pterogobius elapoides (serpentine goby), dominant component of fish assemblage in shallow rocky areas off the coast in Korea and Japan. Although most other gobies are primarily benthic carnivores, P. elapoides is a semipelagic fish; however, little is known about how those species change their foraging tactics with growth. In our diet analyses, the most common diet was pelagic copepods and benthic amphipods, and diet shift was observed from pelagic to benthic with growth. The ontogenetic diet shift seems to be the result of the preference for energetically more profitable prey in larger-size classes as well as the results of different prey availability due to among-habitat variation in diet. However, differential food preference does not appear to affect individual scope for searching food. Several factors such as predation pressures and interspecific resource partitioning might contribute to the changes in diet observed among size classes, which were included in our ongoing tests.

Mortalidad natural de Paracalanus indicus (Copepoda: Calanoida) en áreas de surgencia asociada a la zona de mínimo de oxígeno en el Sistema de Corrientes Humboldt: implicancias en el transporte pasivo del flujo de carbono

The in situ natural mortality (predation excluded) and growth rates (g) of the pelagic copepod Paracalanus indicus were studied under variable upwelling regi...

Evolution in the deep sea: Biological traits, ecology and phylogenetics of pelagic copepods

Deep-sea biodiversity has received increasing interest in the last decade, mainly focusing on benthic communities. In contrast, studies of zooplankton in the meso- to bathypelagic zones are relatively scarce. In order to explore evolutionary processes in the pelagic deep sea, the present study focuses on copepods of two clausocalanoid families, Euchaetidae and Aetideidae, which are abundant and species-rich in the deep-sea pelagic realm. Molecular phylogenies based on concatenated-portioned data on 18S, 28S and internal transcribed spacer 2 (ITS2), as well as mitochondrial cytochrome c oxidase subunit I (COI), were examined on 13 species, mainly from Arctic and Antarctic regions, together with species-specific biological traits (i.e. vertical occurrence, feeding behaviour, dietary preferences, energy storage, and reproductive strategy). Relationships were resolved on genus, species and even sub-species levels, the latter two established by COI with maximum average genetic distances ranging from ⩽5.3% at the intra-specific, and 20.6% at the inter-specific level. There is no resolution at a family level, emphasising the state of Euchaetidae and Aetideidae as sister families and suggesting a fast radiation of these lineages, a hypothesis which is further supported by biological parameters. Euchaetidae were similar in lipid-specific energy storage, reproductive strategy, as well as feeding behaviour and dietary preference. In contrast, Aetideidae were more diverse, comprising a variety of characteristics ranging from similar adaptations within Paraeuchaeta, to genera consisting of species with completely different reproductive and feeding ecologies. Reproductive strategies were generally similar within each aetideid genus, but differed between genera. Closely related species (congeners), which were similar in the aforementioned biological and ecological traits, generally occurred in different depth layers, suggesting that vertical partitioning of the water column represents an important mechanism in the speciation processes for these deep-sea copepods. High COI divergence between Arctic and Antarctic specimens of the mesopelagic cosmopolitan Gaetanus tenuispinus and the bipolar Aetideopsis minor suggest different geographic forms, potentially cryptic species or sibling species. On the contrary, Arctic and Antarctic individuals of the bathypelagic cosmopolitans Gaetanus brevispinus and Paraeuchaeta barbata were very similar in COI sequence, suggesting more gene flow at depth and/or that driving forces for speciation were less pronounced in bathypelagic than at mesopelagic depths.

The Global Diversity of Parasitic Isopods Associated with Crustacean Hosts (Isopoda: Bopyroidea and Cryptoniscoidea)

Parasitic isopods of Bopyroidea and Cryptoniscoidea (commonly referred to as epicarideans) are unique in using crustaceans as both intermediate and definitive hosts. In total, 795 epicarideans are known, representing ∼7.7% of described isopods. The rate of description of parasitic species has not matched that of free-living isopods and this disparity will likely continue due to the more cryptic nature of these parasites. Distribution patterns of epicarideans are influenced by a combination of their definitive (both benthic and pelagic species) and intermediate (pelagic copepod) host distributions, although host specificity is poorly known for most species. Among epicarideans, nearly all species in Bopyroidea are ectoparasitic on decapod hosts. Bopyrids are the most diverse taxon (605 species), with their highest diversity in the North West Pacific (139 species), East Asian Sea (120 species), and Central Indian Ocean (44 species). The diversity patterns of Cryptoniscoidea (99 species, endoparasites of a diverse assemblage of crustacean hosts) are distinct from bopyrids, with the greatest diversity of cryptoniscoids in the North East Atlantic (18 species) followed by the Antarctic, Mediterranean, and Arctic regions (13, 12, and 8 species, respectively). Dajidae (54 species, ectoparasites of shrimp, mysids, and euphausids) exhibits highest diversity in the Antarctic (7 species) with 14 species in the Arctic and North East Atlantic regions combined. Entoniscidae (37 species, endoparasites within anomuran, brachyuran and shrimp hosts) show highest diversity in the North West Pacific (10 species) and North East Atlantic (8 species). Most epicarideans are known from relatively shallow waters, although some bopyrids are known from depths below 4000 m. Lack of parasitic groups in certain geographic areas is likely a sampling artifact and we predict that the Central Indian Ocean and East Asian Sea (in particular, the Indo-Malay-Philippines Archipelago) hold a wealth of undescribed species, reflecting our knowledge of host diversity patterns.

Flexible Feeding Strategies of Juvenile Gray Triggerfish (Balistes capriscus) and Planehead Filefish (Stephanolepis hispidus) Within Sargassum Habitat

Sargassum-associated juvenile gray triggerfish and planehead filefish exhibited flexible feeding strategies in terms of their use of epifauna or pelagic zooplankton. Four diet samples represented instances of co-occurrence and segregated occurrence. Co-occurring gray triggerfish had the most specialized diets consisting mainly of pelagic copepods and hyperiid amphipods. Conversely, segregated triggerfish as well as both co-occurring and segregated filefish had broader diets mainly consisting of Sargassum epifauna, such as bryozoans, portunid crabs, and hippolytid shrimp. Still, co-occurring planehead filefish also consumed somewhat more zooplankton than segregated planehead filefish. Ontogenetic diet transitions were not as distinct for gray triggerfish as for planehead filefish. Our study demonstrates that juvenile tetradonts can be flexible in their use of benthic versus pelagic feeding strategies. Consequently, the influence of these key consumers on Sargassum food webs may vary spatiotemporally.

Age- and size-dependent mating performance and fertility in a pelagic copepod, Temora longicornis

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 442:123-132 (2011) - DOI: https://doi.org/10.3354/meps09402 Age- and size-dependent mating performance and fertility in a pelagic copepod, Temora longicornis Mie Hylstofte Sichlau*, Thomas Kiørboe National Institute of Aquatic Resources, Technical University of Denmark, Kavalergården, 2920 Charlottenlund, Denmark *Email: mhsi@aqua.dtu.dk ABSTRACT: In many species, size and age can be strong determinants of the reproductive success for both sexes. We examined age- and size-dependent reproductive performance (egg and sperm production, mating success) in a pelagic copepod, Temora longicornis. Compared with smaller males, larger males produced larger spermatophores containing more spermatozoa and fertilized a larger fraction of available females. Females mating with large males produced more offspring than those mating with small males. Similarly, large females had higher egg production rates as well as a higher lifetime egg production than did small females. Ageing effects were evident in this species: mortality rate increased and fertility decreased rapidly with age. The average adult longevity under optimal laboratory conditions was 30 d in both males and females, but females produced eggs for only 18 d, and males could fertilize females for only about 8 d after they matured. The strong size- and age-dependent fertility observed in this species is conducive to the development of sexual selection via mate choice for young and large partners, as has been shown in another copepod species. KEY WORDS: Spermatophore · Spermatozoa · Egg production · Ageing · Mortality rate · DAPI · Temora longicornis Full text in pdf format PreviousNextCite this article as: Sichlau MH, Kiørboe T (2011) Age- and size-dependent mating performance and fertility in a pelagic copepod, Temora longicornis. Mar Ecol Prog Ser 442:123-132. https://doi.org/10.3354/meps09402 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 442. Online publication date: December 05, 2011 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2011 Inter-Research.

Growth and Development Rates Have Different Thermal Responses

Growth and development rates are fundamental to all living organisms. In a warming world, it is important to determine how these rates will respond to increasing temperatures. It is often assumed that the thermal responses of physiological rates are coupled to metabolic rate and thus have the same temperature dependence. However, the existence of the temperature-size rule suggests that intraspecific growth and development are decoupled. Decoupling of these rates would have important consequences for individual species and ecosystems, yet this has not been tested systematically across a range of species. We conducted an analysis on growth and development rate data compiled from the literature for a well-studied group, marine pelagic copepods, and use an information-theoretic approach to test which equations best describe these rates. Growth and development rates were best characterized by models with significantly different parameters: development has stronger temperature dependence than does growth across all life stages. As such, it is incorrect to assume that these rates have the same temperature dependence. We used the best-fit models for these rates to predict changes in organism mass in response to temperature. These predictions follow a concave relationship, which complicates attempts to model the impacts of increasing global temperatures on species body size.

Population Differentiation in the Open Sea: Insights from the Pelagic Copepod Pleuromamma xiphias

Although a number of recent studies of marine holoplankton have reported significant genetic structure among populations, little is currently known about the biological and oceanographic processes that influence population connectivity in oceanic plankton. In order to examine how depth preferences influence dispersal in oceanic plankton, I characterized the genetic structure of a copepod with diel vertical migration (DVM) (Pleuromamma xiphias), throughout its global distribution, and compared these results to those expected given the interaction of this species' habitat depth with ocean circulation and bathymetry. Mitochondrial COI sequences from 651 individuals from 28 sites in the Indian, Pacific, and Atlantic Oceans revealed highly significant genetic differentiation both within and among ocean basins. Limited dispersal among distinct pelagic provinces seems to have played a major role in population differentiation in this species, with strong genetic breaks observed across known oceanographic fronts or current systems in all three ocean basins. The Indo-West Pacific (IWP) holds a highly distinct genetic population of this species that was sampled in both the western Pacific and eastern Indian Oceans. This suggests that the IWP does not act as a strong barrier to gene flow between basins, as expected, despite the relatively shallow water depth (<200 m) and vertically extensive (>400 m) diel migration of this species. A pattern of isolation by distance was observed in the Indian Ocean with genetic differentiation among samples down to spatial scales of ∼800 km, indicating that realized dispersal in P. xiphias occurs over much smaller spatial scales than in previously reported oceanic holoplankton. Given its highly regionalized population genetic structure, P. xiphias may have some capacity to adapt to local oceanographic conditions, and it should not be assumed that populations of this species in distinct pelagic biomes will respond in the same way to shared physical or climatic forcing.

Metabolic activity of pelagic copepods from 5,000 to 7,000 m depth of the western subarctic Pacific, as inferred from electron transfer system (ETS) activity

This study demonstrates reduced electron transfer system (ETS) activity of mixed copepods collected from 5,000 to 7,000 m depths [3.21 ± 1.25 μl O2 (mg protein)−1 h−1 at 10°C] as compared with mixed copepods from 0 to 200 m depths [5.93 ± 1.66 μl O2 (mg protein)−1 h−1 at 10°C] of the western subarctic Pacific. At the in situ temperature of 1.5°C, the 5,000–7,000 m ETS data, in terms of wet mass (WM)-specific respiration rates (R), is equivalent to [0.052 ± 0.021 μl O2 (mg WM)−1 h−1] which is similar to or greater than those reported for selected copepods or mixed mesozooplankton from <5,000 m depth by previous workers.

Epipelagic copepod distributions in the eastern equatorial Pacific during the weak La Niña event of 2001

We determined the distribution and abundance of pelagic copepods in the eastern equatorial Pacific between the coast of Ecuador and the Galapagos Islands under oceanographic conditions associated with the weak La Nina event of 2001. In September-October 2001, negative anomalies of sea surface temperature from this event still remained in the eastern equatorial Pacific, mainly between Ecuador and the Galapagos Islands. The event allowed the incursion of the Humboldt Current farther north and of the Equatorial Undercurrent into the study area, favouring a strong Equatorial Front and upwelling processes. There was evidence of mesoscale eddies in the study area and of the presence of the South Equatorial Current going westward at about 1°N. We identified 107 copepod species and analyzed the distribution of the 10 most abundant ones: Oncaea venusta, Subeucalanus pileatus, S. crassus, S. subtenuis, Paraeucalanus attenuatus, Pleuromamma borealis, Scolecithrix danae, Clausocalanus farrani, Temora discaudata and Calanus chilensis . Copepod distribution and abundance exhibited marked latitudinal differences related to the oceanographic conditions; abundance was highest to the southeast of the Galapagos Islands. Oncaea venusta, Pleuromamma borealis, Calanus chilensis , and Subeucalanus subtenuis were the species that best defined the Equatorial Front and the upwelling process.

Senescence and sexual selection in a pelagic copepod.

The ecology of senescence in marine zooplankton is not well known. Here we demonstrate senescence effects in the marine copepod Oithona davisae and show how sex and sexual selection accelerate the rate of ageing in the males. We show that adult mortality increases and male mating capacity and female fertility decrease with age and that the deterioration in reproductive performance is faster for males. Males have a limited mating capacity because they can fertilize < 2 females day−1 and their reproductive life span is 10 days on average. High female encounter rates in nature (>10 day−1), a rapid age-dependent decline in female fertility, and a high mortality cost of mating in males are conducive to the development of male choosiness. In our experiments males in fact show a preference for mating with young females that are 3 times more fertile than 30-day old females. We argue that this may lead to severe male-male competition for young virgin females and a trade-off that favours investment in mate finding over maintenance. In nature, mate finding leads to a further elevated mortality of males, because these swim rapidly in their search for attractive partners, further relaxing fitness benefits of maintenance investments. We show that females have a short reproductive period compared to their average longevity but virgin females stay fertile for most of their life. We interpret this as an adaptation to a shortage of males, because a long life increases the chance of fertilization and/or of finding a high quality partner. The very long post reproductive life that many females experience is thus a secondary effect of such an adaptation.

Structure and seasonal variability of fish food webs in an estuarine tropical marine protected area (Senegal): Evidence from stable isotope analysis

West African tropical estuaries play an important role in the growth and survival of many commercially exploited fish species and enable the sustainability of considerable artisanal fishery yields. However, their trophic functioning remains poorly understood. In the Sine Saloum estuary (Senegal), a marine protected area (MPAs) was designated in 2003 to manage fisheries resources. The present study aimed to determine the structure, trophic functioning and seasonal patterns of the fish assemblages in this MPA. Throughout the study, 28 fish species were collected, with higher values of biomass (3826 kg km −2) recorded during the wet season and lower values during the dry season (1228 kg km −2). Fish assemblages in both seasons were dominated by species with marine affinity, which accounted for 87% of the total biomass in the wet season and 70% in the dry season, with their abundance varying from 83% to 57%, respectively. Based on stable isotopic composition (δ 13C and δ 15N), species were combined into trophic groups. Primary consumers were partitioned into suspensivores (pelagic copepods, oysters and mussels), which fed mainly on particulate organic matter, and intermediate consumers, feeding on freshly deposited organic matter and benthic microalgae ( Sarotherodon melanotheron and Arca senilis). Secondary consumers were divided into three groups. The first group included mullet, which fed by grazing on benthic microalgae (benthic affinity feeders). The second group, pelagic affinity feeders, was the most heterogeneous and fed mainly on pelagic components. The last secondary consumer group termed the intermediate group, included piscivores and benthic and pelagic invertebrate feeders, which dominated the top of the food web. The food chain in October was lengthened due to the occurrence of tertiary consumers. Food webs were dominated by secondary consumers, which constituted 89% of total biomass in the dry season and 71% in the wet season. The fish food web varied largely with season in faunal composition and food chain length. This study highlighted the need to take into account the seasonal dynamic of the food web both in terms of composition and structure to assess carbon fluxes in tropical estuaries.

What makes pelagic copepods so successful?

Three features that are unique or almost unique to pelagic copepods among zooplankton may account for their numerical dominance in the pelagic realm of the oceans: (i) the torpedo-shaped body, the sensory armed antennules and the ‘gearing’ of the muscle motor make pelagic copepods very efficient in detecting and escaping predators. The specific force production and velocities during escape jumps are both about an order of magnitude higher than for other similarly sized organisms. (ii) The capability to remotely detect prey and to either capture these as they arrive in a scanning current, or as they swim through the perceptive sphere of the copepod, releases the copepods from the penalties associated filtering sticky water for prey particles. Scanning currents and active attack jumps are found in only few other zooplankters. (iii) Efficient mate finding in a mate-dilute environment allows for sexual reproduction with actual mating in each generation, otherwise uncommon in the plankton, and yields advantages in terms of deleting bad mutations and promoting ‘good genes’ through sexual selection.

Taxonomic re-examination and distribution of copepods reported as Oncaea notopus Giesbrecht, 1891 (Copepoda, Oncaeidae) in the Mediterranean Sea

A new species of the pelagic marine copepod family Oncaeidae, Oncaea serrulata, is described from the Mediterranean Sea. The species belongs to the notopus-group of Oncaeidae, which are characterized by a long, free exopod on leg 5. It differs from Oncaea notopus Giesbrecht 1891 and any other described species of this group by a combination of morphological characters, including: (1) the relative lengths of distal endopod spines on swimming legs 2 and 3, (2) the denticulate ornamentation of the exopod segment and the two exopodal setae on leg 5, (3) the proportional lengths of the caudal setae, and (4) the comparatively small body length. The species occurs widespread in the Mediterranean Sea in mesopelagic and deep-sea layers down to 3,000 m depth and was also found in near-bottom sediment traps moored at a bottom depth of 2,347 m in the Ligurian Sea. O. serrulata appears to be the only representative of the notopus-group in the Mediterranean Sea and seems to have consistently been confounded with the allegedly cosmopolitan O. notopus Giesbrecht in most earlier studies in this area. The taxonomic history of Giesbrecht’s O. notopus, which was originally described from the Pacific, is summarized and morphological identification parameters applicable for the species identification of notopus-type oncaeids are discussed. In the future, identification may be facilitated by using genetic barcodes in comparison with those recently analysed for the Mediterranean O. serrulata (as Oncaea sp. 7 sensu Bottger-Schnack 1997). Published data on the zoogeographical and vertical distribution as well as the abundance of notopus-type oncaeids in the Mediterranean Sea are reviewed. Possible causes for the lack of positive records of this taxon in Mediterranean studies earlier than 1980 are discussed.