Late Copepodite Stages Research Articles

Life history of Calanus finmarchicus in the Norwegian Sea in relation to planktivorous fish

This paper is focused on the potential impact of planktivorous fish in shaping the life history of Calanus finmarchicus in the Norwegian Sea. It is suggested that seasonally migrating fish species influence the timing of spawning and descent, and hence the number of generations of C. finmarchicus annually, and that the presence of resident mesopelagic fish influences the selection of winter habitat. C. finmarchicus ascends from overwintering and starts spawning 1-2 months prior to the spring bloom, which is exploited by the developing copepodites. Mortality risks increase upon arrival of fish on their oceanic feeding migrations, which for herring is prior to the spring bloom. Spawning early in the season may therefore reduce parental risks of exposure to such predators. Late-stage copepodites are heavily exploited by seasonally migrating fish during summer, so representing a driving force for the seasonal descent of C. finmarchicus. Overwintering takes place below the main domain of mesopelagic fish.

Response of life history traits to food conditions in a cyclopoid copepod from an oligotrophic environment

The Cyclops sp. responses of life history traits (growth, development, and reproduction) to food conditions from oligotrophic Lake Toya were analyzed by rearing animals individually under four food regimes:three densities of the alga Cryptomonas tetrapyrenoidosa and nauplii of the calanoid copepod Eurytemora affinis as prey in an algal suspension. Cyclops sp. grew successfully from newborn nauplii to adults when algal density was ≥4 × 103 cells ml‐1 . Development time was shorter and body length larger in the high‐density (H) treatment (4 × 104 cells ml‐1 ) than in medium‐density (M) treatment (4 × 103 cells ml−1) until the early copepodite stages. In late copepodite stages, females tended to grow more slowly but tended to be larger in the M treatment than in the H treatment. However, stage‐specific growth rates were similar among treatments during development, suggesting a trade‐off between body size and development time. Although the egg production rate was higher in the M treatment than in the H treatment, it depended on female body size regardless of the food regime. Furthermore, the weight‐specific egg production rate was the same among treatments, indicating egg production was not affected by the algal concentrations tested. Addition of copepod prey influenced neither postembryonic development time nor body size, and egg production rates were comparable to those reared with an algal diet. These results reveal that even older copepodites and adults, which are generally thought to be predacious, do not necessarily require animal prey for growth and reproduction, and that Cyclops sp. can complete its life cycle on an algal diet alone. For female Cyclops sp., reduction of algal density resulted in slow development and large body size, which might be an adaptation to the oligotrophic environment, the original habitat of the copepod.

Transport of marine fish larvae to Saroma-ko Lagoon (Hokkaido, Japan) in relation to the availability of zooplankton prey under the winter ice cover

Copyright (c) 1996 Elsevier Science B.V. All rights reserved. To assess the importance of ice-covered Saroma-ko Lagoon as a winter nursery area for young fish spawned offshore, we monitored the recruitment of marine fish larvae from the Sea of Okhotsk to the lagoon as well as the availability of larval fish prey under the ice cover from 24 February to 23 March 1992. Sand lance (Ammodytes sp.r and walleye pollock (Theragra chalcogrammar larvae recruited to the lagoon on flood tide whereas snake prickleback (Lumpenus sagittar larvae were exported to the Sea of Okhotsk on ebb. Before the ice breakup, ice microalgae made up the bulk of the microalgal biomass in the lagoon. The production and release of ice algae did not trigger the maturation of the late copepodite stages of copepods, and the proportion of adult females in the copepod assemblage remained low. The production of copepod nauplii (the main prey of fish larvaer under the ice was probably insufficient to insure suitable feeding and growth of fish larvae entering the lagoon in winter. Sand lance larvae, the most abundant species to colonize the lagoon in February−March, had to survive for nearly two months at low food abundance. Based on our results, the importance of Saroma-ko Lagoon as a winter nursery area for fish larvae appears negligible.

Krill-copepod interactions at South Georgia, Antarctica, I. Omnivory by Euphausia superba

Feeding by juvenile Antarctic krill Euphausia superba near South Georgia was assessed during the austral summer of 1995/1996. Gut fluorescence results were compared with those from incubations in natural seawater and seawater enriched with phytoplankton and zooplankton. In natural seawater, with typically low food concentrations (median 56 mg C m-3) the median ration was 0.68% of krill carbon d-1. Phytoplankton dominated carbon in the natural incubation water but dinoflagellates, ciliates and small calanoid copepods dominated the carbon intake of krill. In both natural and enriched water, maximum clearance rates were on 1 to 3 mm calanoid copepods. Copepods larger than this (e.g. late copepodite stages of Calanoides acutus and Rhincalanus gigas) were cleared more slowly despite dominating the carbon in the enriched incubations. Oithona spp. were cleared more slowly than calanoids of similar size, despite their greater abundance and their similar contributions to available carbon. These trends could reflect detection/escape interactions between krill and copepods. With enriched food, copepods dominated krill diet, krill rations exceeded 10% of body carbon d-1 and rations did not appear to reach a plateau even at food concentrations of ~1 g C m-3. This suggests that krill could feed rapidly during periodic encounters with layers or patches of zooplankton. Gut fluorescence revealed gut passage times of 3.7 to 6.3 h and an algal carbon ration of 0.43% d-1, thus supporting the low algal carbon rations derived from the incubations. Published acoustic values of mean krill biomass north of South Georgia that summer of 8.3 g dry mass m-2 were combined with their clearance rates to give estimates of krill removing daily 0.2% of phytoplankton standing stocks, 0.6% of protozoans and 1.6% of small calanoid copepods. This impact on copepods is much higher than previous estimates from Antarctic amphipods and chaetognaths. The long generation times of Antarctic copepods mean that krill were potentially important predators of small copepods during our study.

Effects of Zooplankton Grazing on Phytoplankton Size-Structure and Biomass in the Lower Hudson River Estuary

The impact of mesozooplankton (>210 μm, mostly adult copepods and late-stage copepodites) and micrometazoa (64–210 μm, mostly copepod nauplii) on phytoplankton size structure and biomass in the lower Hudson River estuary was investigated using various14C-labeled algal species as tracers of grazing on natural phytoplankton. During spring and summer, zooplankton grazing pressure, defined as %=mg C ingested m−2 h−1/mg C produced m−2 h−1 (depth-integrated rates)×100, on total phytoplankton ranged between 0.04% and 1.9% for mesozooplankton and 0.1% and 6.6% for micrometazoa. The greatest grazing impact was measured in fall when 20.2% and 44.6%, respectively, of the total depth-integrated primary production from surface water phytoplankton was grazed. Mesozooplankton exhibited some size-selective grazing on phytoplankton, preferentially grazing the diatomThalassiosira pseudonana over the larger diatomDitylum brightwelli, but this was not found for micrometazoa. Neither zooplankton group grazed on the dinoflagellateAmphidinium sp. We conclude that metazoan zooplankton have a minimal role in controlling total phytoplankton biomass in the lower Hudson River estuary. Differences in the growth coefficients of various phytoplankton size-fractions—not grazing selectivity—may be the predominant factor explaining community size-structure.

Subantarctic copepods in an oceanic, low chlorophyll environment:ciliate predation, food selectivity and impact on prey populations

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 130:85-96 (1996) - doi:10.3354/meps130085 Subantarctic copepods in an oceanic, low chlorophyll environment: ciliate predation, food selectivity and impact on prey populations Atkinson A Copepod feeding rates and food selectivity were measured at an oceanic subantarctic site over 5 d in February 1994. A series of gut fluorescence and gut evacuation experiments was carried out for species ranging in size from Oithona similis to Pleuromamma robusta. The copepods were also incubated in ambient seawater to compare their clearance rates on ciliates, diatoms and total chlorophyll a (chl a), using microscope counts and chlorophyll budgets. Mesozooplankton were concentrated into the top 50 m layer where biomass was high (5.5 g dry mass m-2) and comprised mainly (65%) of copepods. Copepod biomass was dominated by copepodite CV of Calanus simillimus. Numerically, however, Oithona spp. (mainly O. similis) constituted 85% of the copepods. These 2 species dominated copepod grazing and contributed to community grazing in about equal proportions. Chl a concentrations were low (~0.7 mg m-3) and were comprised of mostly nano- and picoplankton. Low daily phytoplankton carbon rations were derived from the 2 methods which measured total chl a consumption. These ranged from 1.5% (female CVI C. simillimus) to 34% of body carbon (late stage copepodites of Oithona spp.). These values were generally well below their estimated respiratory requirements, and probably reflected phytoplankton shortage because clearance rates were fairly high. Clearance rates for total chl a in the incubations tended to be less than those for the counted taxa &GT10 um, suggesting that some of the chl a was in cells too small to be eaten. Feeding selectivity followed a similar pattern across the 4 incubations. Highest clearance rates were on ciliates (~15 um), dinoflagellates (~20 um) or the diatom Corethron sp. (~200 um). Ciliates and dinoflagellates were cleared faster than centric diatoms of similar overall dimensions. It is suggested that the copepods were preying on protozoans preferentially, in response to phytoplankton shortage. Allometric relationships were used to derive the grazing and predation impact of the whole copepod community on primary production and estimated ciliate production. Less than 4% of primary production was removed per day. Copepod predation on ciliates was higher: 57% of daily production, assuming a net growth rate for ciliates of 0.1 d-1. Subantarctic . Copepods . Selective feeding . Ciliates . Allometry Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 130. Publication date: January 11, 1996 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1996 Inter-Research.

Diel feeding behavior and ingestion rate in the copepod Calanus finmarchicus in the southern Gulf of Maine during late spring

In situ feeding was measured on late stage Calanus finmarchicus in the southern Gulf of Maine during late spring 1988 and 1989. The region is a spring feeding ground for the planktivorous right whale, Eubalaena glacialis. Measurements in 1988 were made during the declining spring bloom, when phytoplankton showed considerable spatial variability. 1989 observations were made after summer stratification had become established, when phytoplankton biomass was low and dominated by the <7 μm size fraction. In situ ingestion rates of C. finmarchicus reflected these differences in food, and ranged from 30.2% body C day −1 at a spring bloom station to 0.6% body C day −1 after stratification. These values compare with a maximum ingestion rate of 44.3% body C day −1 measured in a shipboard grazing experiment using cultured algae as food, and indicate that C. finmarchicus became food limited in the southern Gulf of Maine after stratification. Calanus finmarchicus diet feeding behavior and diet vertical migration patterns changed during the seasonal progression from spring bloom to summer stratification. Diet feeding rhythms and vertical migration were absent during the bloom, but developed as the bloom declined. During the post-bloom stratified conditions, diet feeding rhythms continued but vertical migration ceased. Most of the C. finmarchicus population remained near the surface, while a small population of nonmigratory individuals resided at depth and appeared to be feeding upon sedimented spring bloom diatoms. At the spring bloom station C. finmarchicus ingested only a small proportion of the phytoplankton standing stock in the > 7 μm size fraction (2.9% day −1), reflecting the high biomass of phytoplankton and the stage composition of the C. finmarchicus population, dominated by early copepodite stages with low biomass. In contrast, at the post-bloom stations in 1989, the dense surface aggregations of C. finmarchicus populations were dominated by late copepodite stages whose total biomass was comparable to that of the phytoplankton, and C. finmarchicus consumed a significantly larger fraction of the > 7 μm phytoplankton standing crop (up to 62.5% day −1.

Calanoid copepod grazing on phytoplankton: seasonal experiments on natural communities

Calanoid copepods are major components of most lacustrine ecosystems and their grazing activities may influence both phytoplankton biomass and species composition. To assess this we conducted four seasonal, in situ, grazing experiments in eutrophic Lake Rotomanuka, New Zealand. Ambient concentrations of late stage copepodites and adults of calanoid copepods (predominantly Calamoecia lucasi, but with small numbers of Boeckella delicata) were allowed to feed for nine days on natural phytoplankton assemblages suspended in the lake within 1160 litre polyethylene enclosures. The copepods reduced the total phytoplankton biomass of the dominant species in all experiments but were most effective in summer (the time of highest grazer biomass) followed by spring and autumn. In response to grazing pressure the density of individual algal species showed either no change or a decline. There were no taxa which increased in density in the presence of the copepods. The calanoid copepods suppressed the smallest phytoplankton species (especially those with GALD (Greatest Axial Linear Dimension) < µm) and there appeared to be no selection of algae on the basis of biovolume. Algal taxa which showed strong declines in abundance in the presence of the copepods include Cyclotella stelligera, Coelastrum spp., Trachelomonas spp., Cryptomonas spp., and Mallomonas akrokomos. Calanoid copepods are considered important grazers of phytoplankton biomass in this lake. The study supports the view that high phytoplankton:zooplankton biomass ratios and large average algal sizes characteristic of New Zealand lake plankton may, at least partly, be caused by year round grazing pressure on small algae shifting the competitive balance in favour of larger algal species.

Calanoides acutus in Gerlache Strait, Antarctica II. Solving an inverse problem in population dynamics

Abstract A population dynamics model of the overwintering Southern Ocean copepod, Calanoides acutus , was constructed based on field observations of abundance in the Gerlache Strait during November 1989. We used an analytical solution to solve an inverse problem to determine rates of stage-specific mortality and development as the population emerged from overwintering diapause. Model predictions of mortality rates for CIV, CV and CVI copepodites were 0.068, 0 and 0.131 day −1 , respectively. Best fit solutions of the model predict that late-stage copepodites emerge from diapause by “pulse moulting;” overwintering copepodites appear to emerge from diapause en masse in a relatively brief period prior to the annual spring bloom, rather than moulting at the comparatively slow rates observed in summer. We suggest that the modelling approach we used may have application to many species of copepods whose populations overwriter.

Calanoides acutus in Gerlache Strait, Antarctica. I. Distribution of late copepodite stages and reproduction during spring

Calanoides acutus in Gerlache Strait, Antarctica. I. Distribution of late copepodite stages and reproduction during spring

Lipid class and fatty acid composition of Calanus finmarchicus (Gunnerus), Pseudocalanus sp. and Temora longicornis Muller from a nutrient-enriched seawater enclosure

Adult and late copepodite stages of Calanus finmarchicus (Gunnerus), Pseudocalanus sp. and Temora longicornis Muller sampled from a nutrient-enriched seawater enclosure containing a natural phytoplankton population were all rich in neutral lipid. Pseudocalanus sp. and C. finmarchicus contained mainly wax esters (WE) whereas T. longicornis contained mainly triacylglycerols (TAG). The WE of C. finmarchicus were characteristically rich in 16:0,20:1(n-9) and 22:1(n-11) fatty alcohols and 28% of the WE fatty acids were (n-3) polyunsaturated fatty acids (PUFA). Low levels of TAG in C. finmarchicus contained 28% of their fatty acids as (n-3) PUFA. The fatty alcohols of WE in Pseudocalanus sp. were primarily 16:0 and 14:0, with traces of 20:1(n-9) and 22:1(n-11). Of the WE fatty acids, 37% were (n-3) PUFA which was similar to the percentage of (n-3) PUFA in the TAG of this species. Triacylglycerols of T. longicornis contained 48 % of their fatty acids as (n-3) PUFA while the small amounts of WE in this species contained 45% (n-3) PUFA. The WE of T. longicornis contained primarily 16:0, 18:0, 20:1(n-9),22:1(n-11) and 24:0 fatty alcohols. The data are discussed with particular reference to the abundance and retention of (n-3) PUFA in marine food chains.

Particle rejection by Calanus pacificus: discrimination between similarly sized particles

Particle rejection behavior was studied for late-stage copepodites and adult females of Calanus pacificus collected from La Jolla Bay, California (32oN; 117oW) in spring and summer of both 1979 and 1982. Several particles of approximately the same size were offered, both singly and in mixtures, to C. pacificus. In the first set of experiments the copepods were presented with choices between a diatom, Thalassiosira weissflogii (13.1 μm equivalent spherical diam), and polystyrene beads of two sizes (11.1 and 16.5 μm diam). In the second set of experiments they were presented with choices between one of two dinoflagellates, Gyrodinium dorsum (27 μm diam) or Peridinium trochoideum (22 μm diam), and polystyrene beads of three sizes (15, 20 and 25 μm diam). When offered mixtures of cells and beads, the filtration and ingestion rates were significantly greater on the cells than on the beads, irrespective of bead size. We also find that C. pacificus demonstrates a clear preference for G. dorsum relative to P. trochoideum. Our results cannot be explained by a model of passive, size-selective feeding.

Interaction of currents and vertical migration in maintaining Calanus marshallae in the Oregon upwelling zone—a simulation

The zonal distribution of five life stage categories (egg, nauplius, early copepodites CI–III, late copepodites CIV–V, and adult) of the neritic copepod Calanus marshallae observed by Peterson, Miller and Hutchinson ( Deep-Sea Research, 26, 467–494, 1979) during coastal upwelling off Oregon in August 1973 is simulated. The model uses linear formulations to express copepod development and mortality and a time-dependent velocity field predicted by a numerical, upwelling circulation model to carry the copepods. Simulations demonstrate how diel vertical migration by adults can interact with upwelling currents to increase the residence time of egg-laying copepods in the nearshore zone. Diel vertical migration by late stage copepodites may enhance rather than retard their offshore transport if they enter waters sinking below the permanent pycnocline 10 to 20 km from the coast. Predicted longshore trajectories of vertically migrating copepods trapped in the region of intense upwelling show a spiral path over the continental shelf. The extent of longshore transport for copepods seaward of this zone is strongly dependent on the structure in the flow field and on the behavior of the copepod; however, vertical migration always tends to retard longshore transport. using the theoretical flow field, the model hindcasts the shape and location of transects needed to sample migrating and non-migrating copepods as the population moved down the coast.

Effects of age and food availability on diel vertical migration of Calanus pacificus

Age-specific differences in diel vertical migration behavior of Calanus pacificus were investigated in a 58 d (30 April–26 June, 1981) experiment in the Scripps Institution of Oceanography Deep Tank, La Jolla, California, USA; the experiment spanned three successive generations of copepods. The onset of vertical migration behavior occurred in the first feeding stage, Nauplius III. The amplitude of vertical migration gradually increased with age, becoming maximal in the late copepodite stages. Night depths remained constant with age while daytime depths increased. The migratory behavior of late copepodite stages was influenced by food availability. When phytoplankton was abundant and individual ingestion rates were high, copepodites performed high-amplitude migrations. As food availability declined, however, and the competition for food increased, migration amplitudes decreased and then ceased altogether so that copepodites remained in the relatively food-rich surface waters at all times. We suggest that hunger is the primary factor controlling vertical migration behavior.

Zooplankton Population Dynamics and Diaptomus Production in Waldsea Lake, a Saline Meromictic Lake in Saskatchewan

Zooplankton population dynamics were monitored in meromictic saline Waldsea Lake, Saskatchewan, during 1974–75. The dominant zooplankton species were Diaptomus connexus, Brachionus plicatilis, Hexarthra fennica, and Daphnia similis. Diaptomus had a 1-yr life cycle. Overwintered late-stage copepodites molted into adults in May and June and were followed by sequential peaks in numbers of eggs, nauplii, and copepodites. The estimated annual production of this species was 0.6 g dry weight∙m−2 or 0.3 g C∙m−2. About 4% of the annual planktonic primary production would be required to support Diaptomus if it is 10% efficient. The standing crop of Brachionus and Hexarthra was highest in the spring and declined thereafter; Hexarthra was more abundant than Brachionus. The standing crop of Daphnia was much lower than that of either rotifer and showed a spring and fall peak in abundance. Differences in vertical distribution were present among the zooplankton species but no real vertical migrations were observed. Key words: Diaptomus connexus, zooplankton, population dynamics, production, saline meromictic lake

Feeding rhythmicity in a migratory copepod (Pseudodiaptomus hessei (Mrázek))

SUMMARY. This paper describes a day/night feeding rhythm in the copepod Pseudodiaptomus hessei in subtropical Lake Sibaya (27°20′ S, 32°40′ E) and examines the origin of this rhythmicity on the basis of field and laboratory observations.Under natural conditions, adult and late copepodite stages (CIV‐CV) of this copepod were predominantly benthic during daylight and migrated at dusk into pelagic waters in which they remained until dawn. Pronounced changes in feeding activity (based on the proportion of animals which contained food in the gut) were associated with this transition from a benthic to pelagic distribution; feeding activity was low by day and high at night. The younger copepodite stages (CI‐CIII) were less strongly benthic during daylight and showed correspondingly less pronounced diel changes in feeding activity.Laboratory experiments involving concurrent light/dark and continuous dark regimes showed that batches of adult and CIV—CV stages fed throughout 24 h, although faecal pellet production increased with time under both light regimes. The laboratory observations are interpreted as negating the possibility that diel differences observed in the field arose through an endogenous feeding rhythm. The possibility that food resources in near‐bottom waters was inadequate to support reasonable feeding activity is rejected on several counts. It is concluded that the feeding rhythm in P. hessei arises from an inferred infaunal distribution during daylight which would preclude filter‐feeding activity. The circumstantial evidence supporting this suggestion is given and the suggestion is evaluated.