Copepod Tigriopus Brevicornis Research Articles

Density-Dependent Metabolic Costs of Copper Exposure in a Coastal Copepod.

Traditional ecotoxicology methods involving copepods have focused on exposure of pooled individuals and averaged responses, but there is increasing awareness of the importance of individual variation. Many biological traits are density dependent, and decisions to use single-individual or pooled exposure may affect responses to anthropogenic stressors. We investigated how conspecific density as a biotic stressor affects behavioral and respiratory responses to copper (Cu) exposure in the coastal copepod Tigriopus brevicornis. Adults were incubated at densities of 1, 2, or 4 individuals per replicate in 3.2 mL of exposure medium (23 µg Cu L-1 or control). Our results show an interaction of Cu exposure and density on respiration. The Cu exposure increased respiration, but this effect diminished with increasing density. We also found reduced swimming activity with increasing density. We propose 2 nonexclusive alternative explanations for the density-dependent respiratory increase of Cu exposure: 1) a behavioral stress response to low conspecific density, or 2) increased Cu exposure due to increased swimming activity. We emphasize the importance of considering density-dependency in responses when designing and interpreting ecotoxicology studies. Environ Toxicol Chem 2021;40:2538-2546. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Analysing individual growth curves for the copepod Tigriopus brevicornis, while considering changes in shape

Understanding growth and development over ontogeny, and the effects of stressors on life history, requires bioenergetic analysis, for example using models based on dynamic energy budget theory. Such analyses require precise and accurate determination of the animal's biomass or biovolume over time. Automated imaging offers great advantages by allowing size measurements at a high temporal resolution and the possibility to follow individual animals, thus providing detailed growth trajectories as well as handles on inter-individual variation in growth. Here we report on a re-analysis of images from a life-cycle experiment with the coastal harpacticoid copepod Tigriopus brevicornis. Biovolume was estimated by approximating the organism's shape by a generalised ellipsoid. This analysis confirmed, rather unsurprisingly, that the moult from the last naupliar to the first copepodite stage is accompanied by a major change in shape. However, within the naupliar and copepodite stages, more gradual elongation was observed. These changes in shape imply that total body length is a poor proxy for body size throughout the developmental stages, and is therefore not suitable for bioenergetic analysis. Volumetric length (cubic root of estimated body volume) is far more appropriate. Interestingly, growth ceases for some 1.5 days around the moult to the first copepodite stage. Such a growth stop was not observed in earlier studies of several other copepod species. Furthermore, the growth rate of the copepodites exceeded that of the nauplii. These complexities in the life history of T. brevicornis pose challenges for bioenergetic analysis that will require determination of additional traits (e.g., feeding and respiration rates) to unravel.

Genotoxic Response and Mortality in 3 Marine Copepods Exposed to Waterborne Copper.

Copper (Cu) is an essential trace metal, but may also be toxic to aquatic organisms. Although many studies have investigated the cytotoxicity of Cu, little is known about the in vivo genotoxic potential of Cu in marine invertebrates. We investigated the genotoxicity of Cu in 2 pelagic calanoid copepods, Acartia tonsa and Temora longicornis, and the intertidal harpacticoid copepod Tigriopus brevicornis by exposing them for 6 and 72 h to waterborne Cu (0, 6, and 60 µg Cu/L). A subsequent 24-h period in filtered seawater was used to investigate delayed effects or recovery. Genotoxicity was evaluated as DNA strand breaks in individual copepods using the comet assay. Copper did not increase DNA strand breaks in any of the species at any concentration or time point. The treatment did, however, cause 100% mortality in A. tonsa following exposure to 60 µg Cu/L. Acartia tonsa and T. longicornis were more susceptible to Cu-induced mortality than the benthic harpacticoid T. brevicornis, which appeared to be unaffected by the treatments. The results show major differences in Cu susceptibility among the 3 copepods and also that acute toxicity of Cu to A. tonsa is not directly associated with genotoxicity. We also show that the comet assay can be used to quantify genotoxicity in individual copepods. Environ Toxicol Chem 2019;38:2224-2232. © 2019 SETAC.

Predation Risk Potentiates Toxicity of a Common Metal Contaminant in a Coastal Copepod.

To examine whether natural stressors like predation risk affect responses to anthropogenic contaminants, we exposed nauplii of the copepod Tigriopus brevicornis to chemical cues from fish (kairomones) and copper (Cu). We tested effects of these treatments, singly and combined, on copepod age and size at maturity, and development stage sensitivity, while controlling for effects of genetic heterogeneity (clutch identity). Predation risk, Cu and clutch identity interacted in their effect on development time. Predation risk alone had minor effects, but potentiated Cu toxicity in the combined treatment by doubling the delay in age at maturity, as compared to Cu exposure alone. This potentiating effect on developmental delay appeared already at the first copepodite stage. The specific strength of response varied among nauplii from different females' clutches. There were no differences in copepod size at maturity among treatments. We did, however, find an interaction between the effect of Cu and clutch identity on copepod growth. Our results demonstrate the importance of ecological interactions for potentiating the toxicity of environmental contaminants. We also demonstrate the need to consider genetic heterogeneity in ecotoxicology. Natural variation in stressor responses has implications for the interpretation of results from toxicological studies using single-clone or inbred culture populations.

The copepod Tigriopus brevicornis (O. F. Müller, 1776) gains UV protection by feeding on UV-acclimated algae

Primary producers exposed to ultraviolet (UV) radiation accumulate a range of metabolites as part of their UV-acclimation response. These metabolites play an important role in plant and algal UV protection. We investigated whether UV protection is transferred to consumers that feed on UV-acclimated algal biomass and showed that the copepod Tigriopus brevicornis (O. F. Muller, 1776) displays increased UV tolerance when fed on UV-acclimated Enteromorpha sp. (Clorophyta). We conclude that dietary transfer of metabolites produced in UV-acclimated biomass underlies the increased UV protection of the copepods. The data emphasise the complexity of the effects of UV radiation on the rock pool ecosystem.

Seasonal and Cyclical Changes in Genetic Composition of the Marine Intertidal Rock Pool Copepod Tigriopus brevicornis.

Tigriopus brevicornis is a marine rock pool copepod widely distributed along Atlantic coasts. Due to the absence of a known dispersal mechanism by free swimming stages, exchanges between populations over long distances are questionable. In order to analyse the evolution of an isolated supralittoral rock pool population, sampling of the copepod was performed monthly during 1 year and compared to samplings over 5 years in the same rock pool, as well as from other rock pools. Using ITS1 analysis, cyclical changes in genetic composition were detected. Our results give clear indications concerning the segregation of the rock pool population and a lack of gene flow among outside populations. A network analysis shows the presence of several shared dominant haplotypes and also singletons differing by one mutation point. F(st) analyses indicate that the main changes occur in autumn and winter. The few analogies of ITS1 sequences with nearby populations may indicate that new migrants must re-colonise the pools from surrounding rock crevices in the intertidal habitat where they may have found a refuge after bad weather conditions.

Phylogeography of the rock-pool copepod Tigriopus brevicornis (Harpacticoida) in the northern North Atlantic, and its relationship to other species of the genus

We investigated relationships among North Atlantic Tigriopus brevicornis populations and their relationships to Mediterranean T. fulvus and North American T. californicus, using crossing experiments and mitochondrial DNA sequencing. All T. brevicornis populations tested were interfertile, while interspecific crosses produced either no offspring or offspring that did not survive past the larval stage, with the exception of a few T. brevicornis × T. californicus crosses that produced mature adults. DNA sequencing of a fragment of mitochondrial cytochrome oxidase I (COI) showed that samples of T. brevicornis from Iceland, the Faroes, Ireland, Scotland and Nova Scotia formed a single shallow clade. In contrast, T. brevicornis from more southern populations in France and Portugal formed a clade with substantially greater branch lengths. Tigriopus brevicornis was monophyletic, and T. brevicornis plus Mediterranean T. fulvus were together also monophyletic. The phylogeography of T. brevicornis closely mirrored that found in T. californicus, with substantially reduced interpopulation divergence at northern latitudes. The known distribution of T. brevicornis in Iceland and the Faroes is shown and dispersal mechanisms and habitat selection briefly discussed.

Metal distributions in Tigriopus brevicornis (Crustacea, Copepoda) exposed to copper, zinc, nickel, cadmium, silver, and mercury, and implication for subsequent transfer in the food web

The marine copepod Tigriopus brevicornis is a benthic microcrustacean inhabiting splashed rock pools in the intertidal zone. The genus has a worldwide distribution, and some species play an important role as a link in trophic webs. It is well established that many crustaceans are able to survive in contaminated environments by storing metallic pollutants in detoxified form, and thus, they may represent a source of contaminants for their predators. The present study was designed to determine the distribution of bioaccumulated metals, both essential and nonessential, with a view to assessing their availability to the next trophic level. Groups of 1000-1500 adult copepods were exposed for 1-14 days to Ag, Cd, Cu, Hg, Ni, and Zn in water. Three concentrations, chosen to be realistic in comparison with those encountered in polluted environments, were tested for each metal. Copepods were homogenized and metals were analyzed in supernatants (i.e., metals stored in soluble form in soft tissues or easily remobilized from the exoskeleton) and pellets (including metal-rich detoxificatory granules or with cellular debris) recovered after centrifugation. Another experiment, consisting of desorption tests, was designed to evaluate the fraction of metals loosely bound onto the exoskeleton. The bioaccumulation ability is highly variable, as shown by the ratios between the concentrations reached in T. brevicornis experimentally exposed to different metals (at higher dose and at day 14) and those in controls (7, 12, 18, 26, 53, and 99, respectively, for Zn, Cu, Ni, Cd, Ag, and Hg). Cu, Zn, and Ni concentrations in copepods increased linearly with time over the whole range of exposure concentrations, whereas a plateau body metal concentration was reached with time particularly at the highest exposure concentrations for Cd, Ag, and Hg. Metals bound onto the exoskeleton were remobilized to different extents, the percentages of desorption being 11, 14, 16, 19, 31, and 32, respectively, for Zn, Cd, Cu, Ni, Ag, and Hg. Metals mainly present in the supernatant (Cd, Ni, Zn) are probably more able to be transferred along a food chain than those which were equally distributed between soluble and insoluble fractions (Ag, Cu, and Hg).

Genetic differentiation of Atlantic populations of the intertidal copepod <em>Tigriopus brevicornis</em>

The Harpacticoid copepod Tigriopus brevicornis belongs to the meiofauna of intertidal rock pools and is distributed widely along European coasts. Sixteen sites were sampled from the Irish Sea to the coasts of Spain. We used the ITS1 marker to analyse the relationship between the populations because it shows low intrapopulational variation (mean pairwise difference: 1.00 ± 0.8) and high interpopulational divergence (mean pairwise difference: 16.38 ± 7.39). A total of 57 bp out of 433 bp were recognised as informative nucleotides among the 61 individuals analysed. The analysis of the genetic relationships highlighted a north-south split in the distribution of the natural populations and showed a genetic break point around the Gironde estuary, which is probably due to differences in the geomorphologic characteristics of the coastal area on the two different sides of this estuary. Various populations were isolated and the ITS1 sequences indicated that there are specific genetic signatures in these populations. The northern set of populations, which was sampled along a large rocky coastline, had a metapopulation structure with genetic exchanges between geographically close populations and also between geographically far ones. The southern set of populations, which was sampled in small rocky pools on large sandy beaches, showed isolated populations as a consequence of the geomorphology of the area.

The effect of environmental variation on the reproductive development time and output of the high-shore rockpool copepod Tigriopus brevicornis

The extreme environmental changes observed in high-shore rockpools occupied by Tigriopus brevicornis, provide a significant physiological challenge that may have implications for the energetics and hence the life history characteristics of this species. The present study was designed to assess the effect of this environmental variation on the reproductive development time and output of T. brevicornis in terms of duration of the various stages in ovary and egg sac development and maturation as well as naupliar development time to the first copepodite stage and total numbers of copepodites produced. There was a significant difference in reproductive development time and output in the three test salinities with only successful development to copepodite I stage seen in normal seawater (35 psu). There was also a successful release of nauplii seen at the low salinity (5 psu), but no subsequent survival to the copepodite I stage, whilst there was not even a development of egg sacs in the high salinity test medium (70 psu). There was also a significant difference in reproductive development times in the three test temperatures with fastest ovary development in the high temperature (23 °C) and slowest development time in the lowest temperature (5 °C). However, it should be noted that the highest number of nauplii produced was actually in the mid temperature (12 °C), not the high temperature. Exposure to hypoxic and anoxic conditions had a significantly detrimental effect on reproductive development with slower development time through the reproductive stages and no individuals surviving to copepodite stage I from the hypoxic and anoxic test conditions, but good development from the normoxic conditions. The present study indicates that animals living in high-shore rockpools may incur a considerable energetic cost, due to the environmental changes that are characteristic of this habitat and the importance of resource allocation in these different physiological conditions is paramount to the species' survival.

Insoluble detoxification of trace metals in a marine copepod Tigriopus brevicornis (Müller) exposed to copper, zinc, nickel, cadmium, silver and mercury

The marine harpacticoid copepods Tigriopus brevicornis were collected along the French Atlantic Coast (Loire Atlantique) and subsequently exposed to different lethal and sublethal concentrations of various metals (copper, zinc, nickel, cadmium, silver and mercury) for varying lengths of time. Ultrastructural investigations of control and experimentally exposed copepods were performed to investigate the intracellular localization of metals using transmission electronic microscopy (TEM). Copepod digestive epithelium cells as well as the cuticular integument were found to be the major metal storage tissues. Different types of metal-containing granules were found in both metal-exposed copepods and the controls: (1) within lysosomes, (2) in intracellular calcospherites and (3) in extracellular tiny granules. The elemental composition of the granules was determined on ultrathin sections by means of energy dispersive X-ray spectroscopy (EDS). The results were interpreted by considering previous data in order to understand how Tigriopus brevicornis copes with the presence of metals in its environment.

Mobility and potential toxicity of sediment-bound metals in a tidal estuary

Sediment toxicity in the Gironde Estuary, France, a site contaminated by such trace metals as Cd, Cu, and Zn, was examined monthly from March to October 1997, using concurrently geochemical procedures to assess the mobility of contaminants and ecotoxicity tests with invertebrate larvae (the oyster Crassostrea gigas, the sea urchin Paracentrotus lividus, and the copepod Tigriopus brevicornis). Higher mobility of Cd than of Cu and Zn was shown by desorption tests. Both the gross concentrations of Cu and Zn in the sediment and the mobility of these metals showed a temporal evolution, and changes in the toxicity of the sediment to invertebrate larvae generally were observed concomitantly. Little damage was registered in the spring, and greater damage was found in the summer and fall. Positive correlations were shown between mortality in copepods or abnormalities in oyster larvae with the quantities of metals remobilized from sediment at pH 4. On the contrary, no clear temporal trend was shown for total PAH levels in sediment. These correlations and previous toxicological data suggest that sediment-bound metals, particularly Cu and Zn, possibly play a role in biological responses.

Sensitivity of Embryotoxicity Test with Mytilus Galloprovincialis (Lmk) Towards Some Compounds of Environmental Interest (Copper and Pesticides)

Some compounds of environmental interest were investigated using the toxicity test with early life stage of bivalve molluscs. Three pesticides (Carbofuran, Atrazine and Malathion), for which literature data are available only for some species of oysters, were tested with Mytilus galloprovincialis (Lmk). The toxicity of copper was investigated both with M. galloprovincialis and with Crassostrea gigas (Thunberg). Bioassays highlighted a good sensitivity towards the compounds, with EC50 values in the order of mg l-1 for the pesticides and ofμg l-1 for copper. Comparison with other toxicity tests for aquatic environments showed that embryotoxicity test with bivalve is slightly more sensitive than embryotoxicity test with the sea urchin Paracentrotus lividus (Lmk), remarkably more sensitive than Microtox® test but less sensitive than tests with the copepod Tigriopus brevicornis.

Impact of the ‘Erika’ oil spill on the Tigriopus brevicornis ecosystem at the Le Croisic headland (France): preliminary observations

An investigation of the oil spill after the wreck of the tanker ‘Erika’ on 16 December 1999 showed that the maritime area around the town of Le Croisic (between the Vilaine and Loire river estuaries) was severely contaminated by the resulting black tide. Samples of sediment, oil and water were collected during several missions to the Le Croisic headland and analysed. The toxicity of the oil was tested on two organisms, the harpacticoid copepod Tigriopus brevicornis and the alga Enteromorpha intestinalis. The tests showed only slight degradation of the oil after three months. In laboratory conditions, the toxicity of the sediment contaminated by the oil was apparent on the copepod after four days of exposure. Seawater in contact with the oil also had an effect on the alga.

Hanging on in there - position maintenance by the high-shore rockpool harpacticoid copepod Tigriopus brevicornis

The high-shore rockpool habitat of Tigriopus brevicornis is subject to considerable physical disturbance from high spring tides and storms and hence the species must deal with the potential hazard of being swept out. Scanning electron microscopy, video image analysis and flow-through chamber experimentation was used to study the micro-morphology and behaviour of T. brevicornis to understand the position maintenance capabilities of the species. Micro-serrations and forward-facing claws on the first swimming leg combined with hooks on the caudal furcae appear to be the major morphological structures used in position maintenance. Morphological comparisons are made with the subtidal sand-dwelling harpacticoid Harpacticus flexus. The ability of T. brevicornis to burrow into loose sediment is also discussed.

The effect of salinity change on the oxygen consumption and swimming activity of the high-shore rockpool copepod Tigriopus brevicornis

Tigriopus brevicornis is the dominant member of the fauna in high-shore rockpools (above the mean high water of spring tides) that are subject to extreme environmental variation especially in salinity due to infrequent tidal inundation. The present study was designed to assess the effect of large-scale salinity change on the rate of oxygen consumption and levels of activity. Measurements of the rates of oxygen consumption ( V O 2 ) of T. brevicornis in response to simulated changes in salinity (of a magnitude that had previously been recorded in high-shore rock pools inhabited by T. brevicornis) were carried out using closed respirometry. Activity levels of T. brevicornis during exposure to three different salinities (10, 33 and 90 psu) were assessed by means of video image analysis. The study showed that T. brevicornis exhibits a reduction in activity and in oxygen consumption when exposed to higher salinities. However, individuals exposed to low salinities showed elevated rates of oxygen consumption without an associated increase in activity. The present study indicates that animals living in high-shore rockpools may incur a considerable energetic cost, due to the rapid and large-scale environmental changes that are characteristic of this habitat.

Influence of different essential and non-essential metals on MTLP levels in the Copepod Tigriopus brevicornis

Because of their wide geographic distribution, position in the trophic chain, rapid turnover, huge biomass and role in ocean biogeochemical cycles, copepods are regarded as important marine test species. Tigriopus brevicornis Müller, 1776 is a shallow water benthic marine species (Crustacea, Copepoda Harpacticoida). The toxicity of essential and non-essential metals (Ag, Cd, Cu, Hg, Ni and Zn) to Tigriopus brevicornis was determined by 96-h LC 50 testing. Comparative crustacean 96-h LC 50 data in the literature show that Tigriopus brevicornis is a sensitive species suggesting that copepods are good indicators of minimal lethal concentrations of metals. Groups of 1000 to 1500 adult copepods were exposed for 1 to 14 days to metals at concentrations in water, 3 for each metal, considered realistic in comparison with those encountered in polluted environments and far below lethal concentrations, in order to avoid protein metabolism disturbance. The response of Tigriopus brevicornis in terms of MT induction has been examined in specimens exposed to metals. The induction of these proteins and their implication in detoxificatory mechanisms and trophic transfer are discussed.

Behavioural effects of biofouling in a marine copepod

The impact of biofouling by the filamentous bacteria Leucothrix mucor upon the body density and swimming behaviour of the harpacticoid copepod Tigriopus brevicornis was investigated. Biofouled individuals had a greater body density than non-fouled individuals. Biofouled and non-fouled animals swam similar distances and for similar periods of time during trials, but biofouled animals engaged in fewer, but longer bouts of swimming per trial and as a result experienced a lower swimming rate. These observations imply that biofouling has significant implications for the behavioural ecology of T. brevicornis.

Partial purification and enzymatic characterization of acetylcholinesterase from the intertidal marine copepod Tigriopus brevicornis

Marine copepods such as Tigriopus brevicornis are widespread along the Atlantic coast of Europe. These minute crustaceans are highly sensitive to contamination and thus serve as useful bioindicators for the monitoring of pollutant effects. The use of decreased cholinesterase (ChE) activity as a subletal biomarker of exposure to neurotoxic supposes that ChE has been defined in copepods. This study reports the partial purification, separation and characterization of ChE extracted from T. brevicornis. This enzyme is apparently an acetylcholinesterase (AChE) since it hydrolyzed acetylthiocholine iodide at a higher rate than other substrates and was inhibited by eserine but not by iso-OMPA. Electrophoretic studies showed that there is probably a single dimeric form defined by its apparent molecular weight (200 kDa) and sensitivity to inhibitors. The kinetic properties of this ChE were compared with those of other invertebrate ChE.

The effects of temperature and oxygen partial pressure on the rate of oxygen consumption of the high-shore rock pool copepod Tigriopus brevicornis

Inhabitants of littoral rock pools such as the copepod Tigriopus brevicornis are subjected to highly variable physico-chemical conditions. The effect of temperature and P O 2 on the rate of oxygen consumption of T. brevicornis from a Scottish population was studied. As expected, V O 2 increased with increasing temperature over the range 5–30°C. However, at 0 and 35°C the rates of oxygen consumption were significantly lower than predicted. This was reflected in the very different values for Q 10 obtained over the temperature range 0–5°C (due to T. brevicornis entering a dormant state at 0°C) and 30–35°C (due to high mortality at 35°C), compared with the mean Q 10 of 2.9 for the temperature range 5–30°C. Spectrophotometric studies of the body fluids of T. brevicornis failed to detect the presence of a respiratory pigment. Nevertheless, T. brevicornis was able to maintain its rates of oxygen consumption independent of P O 2 under conditions of declining oxygen tension. However, the ability of T. brevicornis to maintain respiratory independence under hypoxia was affected by temperature since the P c was higher at 30°C than at lower temperatures. T. brevicornis appears to be able to withstand exposure to low temperature and to severe hypoxia by entering a quiescent or dormant state during which its metabolic rate is significantly reduced.