Copepod Gut Contents Research Articles

Antioxidant Responses in Copepods Are Driven Primarily by Food Intake, Not by Toxin-Producing Cyanobacteria in the Diet.

The association between oxidative processes and physiological responses has received much attention in ecotoxicity assessment. In the Baltic Sea, bloom-forming cyanobacterium Nodularia spumigena is a significant producer of various bioactive compounds, and both positive and adverse effects on grazers feeding in cyanobacteria blooms are reported. To elucidate the effect mechanisms and species sensitivity to the cyanobacteria-dominating diet, we exposed two Baltic copepods, Acartia bifilosa and Eurytemora affinis, to a diet consisting of toxin-producing cyanobacteria N. spumigena and a high-quality food Rhodomonas salina at 0–300 μg C L−1; the control food was R. salina provided as a monodiet at the same food levels. The subcellular responses to food type and availability were assayed using a suite of biomarkers – antioxidant enzymes [superoxide dismutases (SOD), catalase (CAT), and glutathione S-transferases (GST)] and acetylcholinesterase (AChE). In parallel, we measured feeding activity using gut content (GC) assayed by real-time PCR analysis that quantified amounts of the prey DNA in copepod stomachs. As growth and reproduction endpoints, individual RNA content (a proxy for protein synthesis capacity), egg production rate (EPR), and egg viability (EV%) were used. In both toxic and nontoxic foods, copepod GC, RNA content, and EPR increased with food availability. Antioxidant enzyme activities increased with food availability regardless of the diet type. Moreover, CAT (both copepods), SOD, and GST (A. bifilosa) were upregulated in the copepods receiving cyanobacteria; the response was detectable when adjusted for the feeding and/or growth responses. By contrast, the diet effects were not significant when food concentration was used as a co-variable. A bimodal response in AChE was observed in A. bifilosa feeding on cyanobacteria, with up to 52% increase at the lower levels (5–25 μg C L−1) and 32% inhibition at the highest food concentrations. These findings contribute to the refinement of biomarker use for assessing environmental stress and mechanistic understanding of cyanobacteria effects in grazers. They also suggest that antioxidant and AChE responses to feeding activity and diet should be accounted for when using biomarker profiles in field-collected animals in the Baltic Sea and, perhaps other systems, where toxic cyanobacteria are common.

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.

Mesozooplankton vertical patterns along an east-west transect in the oligotrophic Mediterranean sea during early summer

Mesozooplankton vertical pattern was studied down to 2000 m along an east-west transect in the oligotrophic Mediterranean Sea in June 1999. Depth-stratified samples were collected by a WP-2 net (200 µm mesh size). In addition, the copepod grazing impact on autotrophs was assessed in the epipelagic zone by measurement of small and large copepod gut content by day-night sampling. An east-west increasing trend of integrated total biomass and abundance over the 0–1000 m was detected. Similar vertical pattern of standing stock was found along the transect, with subtle differences at stations positioned over cyclonic and anti-cyclonic gyres. No significant differences were found between stations in the epipelagic and upper mesopelagic zone, except at the westernmost station (NW Mediterranean); discrimination of assemblages between the eastern and the western basins were revealed in the lower mesopelagic and bathypelagic zones. Estimated copepod grazing impact on primary production was found overall higher in the western than in the eastern basin. The entire Mediterranean Sea was dominated by copepod functional groups characterized by reproduction strategies (mostly sac spawners), trophic preferences (mainly omnivores and detritivores) and feeding modes (ambush and cruise feeding), facilitating their adaptation and efficiency in the oligotrophic to very oligotrophic environment of the Mediterranean Sea.

Small copepods could channel missing carbon through metazoan predation.

Global ecosystem models are essential tools for predicting climate change impacts on marine systems. Modeled biogenic carbon fluxes in the ocean often match measured data poorly and part of this could be because small copepods (<2 mm) are modeled as unicellular feeders grazing on phytoplankton and microzooplankton. The most abundant copepods from a seasonal upwelling region of the Eastern North Atlantic were sorted, and a molecular method was applied to copepod gut contents to evaluate the extent of metazoan predation under two oceanographic conditions, a trophic pathway not accounted for in global models. Scaling up the results obtained herein, based on published field and laboratory estimates, suggests that small copepods could ingest 1.79–27.20 gigatons C/year globally. This ignored metazoan‐copepod link could increase current estimates of biogeochemical fluxes (remineralization, respiration, and the biological pump) and export to higher trophic levels by 15.6%–24.4%. It could also account for global discrepancies between measured daily ingestion and copepod metabolic demand/growth. The inclusion of metazoan predation into global models could provide a more realistic role of the copepods in the ocean and if these preliminary data hold true at larger sample sizes and scales, the implications would be substantial at the global scale.

Quantification of copepod gut content by differential length amplification quantitative PCR (dla-qPCR).

Quantification of feeding rates and selectivity of zooplankton is vital for understanding the mechanisms structuring marine ecosystems. However, methodological limitations have made many of these studies difficult. Recently, molecular based methods have demonstrated that DNA from prey species can be used to identify zooplankton gut contents, and further, quantitative gut content estimates by quantitative PCR (qPCR) assays targeted to the 18S rRNA gene have been used to estimate feeding rates in appendicularians and copepods. However, while standard single primer based qPCR assays were quantitative for the filter feeding appendicularian Oikopleura dioica, feeding rates were consistently underestimated in the copepod Calanus finmarchicus. In this study, we test the hypothesis that prey DNA is rapidly digested after ingestion by copepods and describe a qPCR-based assay, differential length amplification qPCR (dla-qPCR), to account for DNA digestion. The assay utilizes multiple primer sets that amplify different sized fragments of the prey 18S rRNA gene and, based on the differential amplification of these fragments, the degree of digestion is estimated and corrected for. Application of this approach to C. finmarchicus fed Rhodomonas marina significantly improved quantitative feeding estimates compared to standard qPCR. The development of dla-qPCR represents a significant advancement towards a quantitative method for assessing in situ copepod feeding rates without involving cultivation-based manipulation.

Quantitative PCR to estimate copepod feeding

Copepods play a central role in marine food webs as grazers of plankton and as key prey for many predators. Therefore, quantifying their specific trophic interactions is critical for understanding the role of copepods in ocean processes. However, because of methodological constraints, it remains difficult to investigate in situ copepod feeding without reliance on laborious intrusive and potentially biased incubation approaches. Recent advances in PCR-based methodologies have demonstrated the feasibility of directly identifying copepod diets based on prey DNA sequences. Yet, obtaining quantitative information from these approaches remains challenging. This study presents results of systematic efforts to develop a quantitative PCR (qPCR) assay targeted to 18S rRNA gene fragments to estimate copepod gut content of specific species of prey algae. These results were first compared to gut content estimates based on fluorescence in the copepod Calanus finmarchicus fed monocultures of two different microalgae species in controlled laboratory studies. In subsequent field studies, we compared feeding rates obtained by microscopy and qPCR for Temora longicornis and Acartia clausi feeding on the haptophyte Phaeocystis globosa in natural blooms. These investigations demonstrate a semi-quantitative relationship between gut content estimates derived from qPCR, gut pigment, and direct microscopy. However, absolute estimates of gut content based on qPCR methodology were consistently lower than expected. This did not appear to be explained by the extraction methods used, or interference by non-target (predator) DNA in the PCR reactions, instead suggesting digestion of prey-specific nucleic acids. Furthermore, the 18S rDNA target gene copy number of the phytoplankton varied with growth phase. Nonetheless, when prey target gene copy number in the ambient water is quantified, the qPCR-approach can be compared to other methods, and then used to semi-quantitatively estimate relative copepod grazing on specific prey in situ without involving further incubations. A distinct advantage of a DNA-based molecular approach compared to gut fluorescence and direct microscopic observation, is the ability to detect non-pigmented and macerated prey. Future studies should aim to correct for breakdown in prey DNA and perform extensive calibrations to other methods in order to achieve a quantitative measure of feeding rates in situ.

Seasonal variation of mesozooplankton biomass, abundance and copepod grazing in the central Cantabrian Sea (southern Bay of Biscay)

Size fractionated mesozooplankton biomass, abundance and copepod grazing were investigated over an annual cycle (1998) at two stations off Cudillero (central Cantabrian Sea). Mesozooplankton biomass was higher in summer/early autumn, reaching ~3000 mg dw m-2 in September. Copepods were the most abundant taxonomic group, representing 91 and 81% of the total mesozooplankton abundance in the coastal and shelf-break station respectively. Copepod gut contents were higher in summer at the coastal station, while the shelf-break station showed maximum gut contents in April. Gut contents were linearly related to integrated chlorophyll, except in the case of large animals at the shelf break station. Copepod community carbon ingestion was higher from June to September at both stations, reaching a maximum value of ~165 mg C m-2 day-1. Calculated grazing rates translates into an average daily consumption values of 8.7% (coast) and 5.25% (shelf-break) of total chlorophyll stock, or 20% (shelf-break) of total primary production.

Mesozooplankton metabolism and feeding in the NW Iberian upwelling

Mesozooplankton size-fractionated biomass, feeding, and metabolic rates were investigated during a cruise conducted off NW Spain in August 1998. Based on different hydrographic conditions observed throughout the study area (upwelling events nearshore and stratified waters offshore), the sampling area was divided into coastal and oceanic zones. Both phytoplankton and mesozooplankton biomass were higher in the coastal upwelling than in the offshore zone. Size structure analysis shows that the small fraction (200–500 μm) of mesozooplankton was more important than the larger fractions (500–1000 μm and >1000 μm) in the open ocean in terms of both biomass and grazing activity. The relationship between copepod ingestion rate and the concentration of chlorophyll a >5 μm resembled a type II functional response. Saturation occurred at the coastal stations, where copepod gut contents were highest. The grazing impact on both phytoplankton biomass and primary production seemed to be higher offshore (5.7 and 12.9%, respectively) than in upwelled waters (5.2 and 5.2%), although the differences were not statistically significant. Phytoplankton ingestion was enough to fulfil the basal metabolism of mesozooplankton in the upwelling area (102.1% of the minimum carbon requirements met) but not in the offshore (45.9%). Feeding activity and metabolic measurements on mesozooplankton point to a herbivorous food web in the coastal upwelling zone and a multivorous food web in the stratified open oceanic waters. The amount of metabolic end products released by mesozooplankton was higher in the coastal zone, but mesozooplankton played a more important role as nutrient regenerators in the multivorous food web (30.3 and 21.7% of the nitrogen and phosphorus phytoplankton demand accounted for ammonium and phosphate excretion, respectively) than in the herbivorous one (3.8% for ammonium and 2.6% for phosphate).

Trophic uptake and transfer of DMSP in simple planktonic food chains

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 31:193-202 (2003) - doi:10.3354/ame031193 Trophic uptake and transfer of DMSP in simple planktonic food chains Kam W. Tang1,3,*, Rafel Simó2 1Danish Institute for Fisheries Research, Kavalergården 6, Charlottenlund 2920, Denmark 2Institut de Ciències del Mar, Passeig Marítim de la Barceloneta 37-49, 08003 Barcelona, Catalonia, Spain 3Present address: Virginia Institute of Marine Science, PO Box 1346, Gloucester Point, Virginia 23062, USA *Email: kamtang@vims.edu ABSTRACT: Recent field studies suggest that a large portion of phytoplankton-DMSP could be lost to grazing by protozoans, but the fate of the grazed DMSP remains uncertain. In the laboratory we studied trophic uptake and transfer of phytoplankton-DMSP through simple planktonic food chains using 2 experimental approaches: (1) A direct approach measured the ingestion and retention of phytoplankton-DMSP by the heterotrophic dinoflagellate Gyrodinium dominans. Overall, DMSP content of G. dominans estimated by the direct approach was highly variable, likely because of the low G. dominans biomass relative to phytoplankton in the samples. (2) An indirect approach, in which the omnivorous copepod Acartia tonsa was allowed to prey on a mixture of phytoplankton and G. dominans. Using this indirect approach, A. tonsa retained a high concentration of G. dominans biomass in its guts. Combined with other feeding parameters, the copepod gut contents were used to derive the DMSP content of G. dominans. When fed on Phaeocystis globosa, G. dominans retained 1.64 x 10-4 nmol DMSP cell-1, or 44% of the grazed DMSP. When fed on Isochrysis galbana, the protozoan retained 6.87 x 10-5 nmol DMSP cell-1, or 32% of the grazed DMSP. A. tonsa selectively preyed on G. dominans when offered a mixture of G. dominans and phytoplankton, deriving 63 to 84% of their dietary DMSP from the protozoan. Our study suggests that protozoans are an important trophic linkage to transfer phytoplankton-DMSP up food chains, and that the effectiveness of this linkage is dependent on the species composition of both the phytoplankton and the higher trophic levels. KEY WORDS: Sulfur cycle · Dimethylsulfide · Dimethylsulfoniopropionate · Microzooplankton · Mesozooplankton Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 31, No. 2. Online publication date: March 13, 2003 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2003 Inter-Research.

First descriptions of early- and middle-stage copepodids of Anthosoma crassum (Dichelesthiidae: Siphonostomatoida) and lesions on shortfin makos (Isurus oxyrinchus) infected with A. crassum.

Early- and middle-stage copepodids of Anthosoma crassum (Dichelesthiidae: Siphonostomatoida) and lesions associated with A. crassum infections are described from samples collected from the jaws of shortfin makos captured off southern California. The copepodids did not possess frontal filaments or frontal organs, and they resided in a headstandlike position firmly attached by their embedded antennae. Copepod larvae and small adults were lodged in shallow mucosal ulcers that basally exhibited mild, acute granulocytic stomatitis; large adults were lodged in deep tunnels encompassing the anterior aspects of their bodies. Some lesions contained more than I copepod. Examinations of lesions revealed that A. crassum infection of shortfin makos can result in severe subacute, necrotizing stomatitis with hemorrhage, granulation tissue, and lymphocytic aggregations in the mucosa, and reactive lymphocytic infiltration of the submucosal skeletal muscle. Copepod gut contents consisted of shark erythrocytes, hemosiderin granules, and necrotic host cells. These observations, along with reports of sharks heavily infected with A. crassum, suggest that this copepod may sometimes play a role in the morbidity and mortality of sharks that it infects.

Mesozooplankton Distribution and Copepod Grazing in the Subtropical Atlantic Near the Azores: Influence of Mesoscale Structures

Mesozooplankton distribution and copepod grazing were investigated in the Subtropical Atlantic Ocean near the Azores during the AZORES I (August) and II (April-May) cruises. Mesozoo- plankton biomass and abundance remained low throughout the region, but significant increases were found related to the presence of the Azores Front. The Azores Front also exhibited maximum values of copepod community ingestion, reaching 250 mg C m-2 ingested daily. This increase in ingestion was related to increases in copepod abundance, but not in copepod gut contents. No relationship was found between gut contents, or ingestion, and phytoplankton biomass or production. Daily cycles were found in copepod gut contents, being higher during the night, but not in copepod abundance. Multi- dimensional scaling analysis revealed differences in copepod taxonomic composition between both sides of the front. During spring, daily copepod ingestion represents an average of 6% of the integrated chlorophyll (Chl) a concentration and 22% of the primary production. These percentages increase to 15% of Chl and 61% of production if we only consider large (>2 µm) phytoplankton. No clear influence of the cyclonic eddy LETICIA was found in mesozooplankton biomass or grazing. A sig- nificant effect of the Great Meteor Tablemount was found in copepod abundance and grazing, with higher values located west of the mount.

Copepod gut contents, ingestion rates and grazing impact on phytoplankton in relation to size structure of zooplankton and phytoplankton during a spring bloom

Copepod gut contents, ingestion rates a s well as the grazing impact on phytoplankton were estimated in coastal waters off Plymouth (SW England) before and during the spring phytoplankton bloom in 1989. A size-fractionation approach was applied, estimating phytoplankton biomass as chlorophyll a concentration in 3 size fractions [pico(0.2 to 2 pm), nano(2 to 10 pm) and microplankton (10 to 100 pm)] and copepod abundances, gut pigment contents and gut evacuation rates in 3 size categories (small, 200 to 350 pm; medium, 350 to 710 pm; and large. > 710 pm). Results showed a direct relation between copepod feeding and the size structure of zooplankton and phytoplankton. Gut pigment contents were higher for the larger copepods and lower for the smaller ones, and increased in parallel with the increase of chlorophyll a concentration and dominance of large cells (> 10 pm) during the spring bloom. Estimations of the grazing impact of the copepod community showed that 5 to 8 % of the total phytoplankton standing stock, and up to between 30 and 40 % of the fraction > 10 Ltm, was grazed during the exponential growth phase of phytoplankton prior to the spring bloom, in contrast to < 2 % and < 5 %, respectively, during other periods before and after the bloom. The medium-sized copepods were responsible for most of this grazing impact, a s a result of their numerical dominance in these coastal waters. Different aspects affecting these estimations of copepod community grazing impact are discussed.

Zooplankton Feeding Ecology: Contents of Fecal Pellets of the Cyclopoid Copepods Oncaea venusta, Corycaeus amazonicus, Oithona plumifera, and O. simplex from the Northern Gulf of Mexico

Abstract. In situ feeding habits of the cyclopoid copepods Oncaea venusta, Corycaeus amazonicus, Oithona plumifera, and O. simplex were investigated by scanning electron microscope examination of fecal pellets, the contents of which reflected copepod gut contents upon capture. Peilet contents were compared with assemblages of phytoplankton present in surface waters at times of copepod collection. All samples were from the northern Gulf of Mexico. All four copepods fed upon phytoplankton and O. venusta also ingested other crustaceans. Dominant components of fecal pellets generally did not mirror those of available phytoplankton assemblages. In some cases, O. venusta ingested primarily larger‐sized particles even when these were not most abundant, and in other cases it did not ingest large cells even when they were present in bloom concentrations. The presence of small (&lt; 2–5 urn diameter) centric diatoms in O. venusta pellets suggests the possibility of feeding by mechanisms other than suspension or raptorial feeding. Limited observations suggest that C. amazonicus and O. plumifera may feed raptorially on larger particles even when these are not particularly abundant, and that the small O. simplex (&lt; 500 nm total length) feeds mainly upon nanoplankton. It appears that cyclopoid feeding mechanisms are complex, and likely more so than those of many calanoids.

Zooplankton feeding ecology: contents of fecal pellets of the copepods Temora turbinata and T. stylifera from continental shelf and slope waters near the mouth of the Mississippi River

In-situ feeding habits of the copepods Temora turbinata and T. stylifera were investigated by scanning electron microscope examination of fecal pellets, the contents of which reflected copepod gut contents upon capture. Pellet contents were compared with assemblages of available phytoplankton in the water column at the times of zooplankton sampling. Samples were collected in continental shelf and slope waters of the Gulf of Mexico near the mouth of the Mississippi River. Both species ingested a wide size range and taxonomic array of phytoplankters, and to a lesser extent, other crustaceans. Fecal pellets contained primarily the remains of the phytoplankters that were most abundant in the water at times of collection. There was considerable overlap in the food items ingested by adult females of both copepod species, or two stages of T. turbinata copepodites. Thus, T. turbinata and T. stylifera are omnivores, but primarily opportunistic herbivores.

Phytoplankton pigments in the gut concents of planktonic copepods from coastal waters off southern California

Phytoplankton xanthophylls in the gut contents of the copepods Calanus pacificus, Corycaeus anglicus, and Paracalanus parvus, collected from 5 stations off San Onofre, California, in June 1982, were measured by reverse phase, high-performance liquid chromatography (HPLC). The dinoflagellate pigment, peridinin, was usually the most abundant xanthophyll in the guts of all three species of copepods. Evidently, feeding was principally on dinoflagellates (which dominated the phytoplankton biomass). The level of feeding activity, rather than the class of phytoplankton ingested, seemed to differentiate the behaviors of the copepods. Xanthophyll content per unit copepod wet weight was higher in Corycaeus anglicus and Paracalanus parvus than in Calanus pacificus. Chlorophyll a fluorescence of the copepod gut contents was measured in conjunction with the analysis of gut xanthophylls. The xanthophyll content of the gut varied directly with the concentration of chlorophyll a in the gut. Xanthophyll content was not related to the concentration of pheopigments in the gut. Apparently, the xanthophylls that were detected were due to the presence of recently ingested phytoplankton biomass.