Common Shore Crab Carcinus Maenas Research Articles

New insights into the evolution of portunoid swimming crabs (Portunoidea, Heterotremata, Brachyura) and the brachyuran axial skeleton

Portunoidea (Heterotremata) is a morphologically disparate taxon of true crabs (Brachyura) best-known for many of its representatives being considered “swimming crabs”. The term “swimming crab”, however, sometimes refers to a distinct taxon (traditionally to Portunidae within Portunoidea), and sometimes to a certain morphotype in which the 5th pereiopod (P5) has a specific shape that facilitates swimming. We use the term “P5-swimming crab” or “P5-swimmer” herein, not only to restrict it to the morphotype, but also to distinguish the swimming in question from other kinds of swimming in Brachyura. The evolution of P5-swimming crabs has not yet been satisfactorily investigated. In particular, it is not known whether the morphotype evolved several times independently in different lineages of Portunoidea or whether it evolved only once and was lost in several lineages. Ours is the first approach combining molecular with morphological data to result in a new phylogenetic positioning of some members of Portunoidea. For the first time, data from the axial skeleton and extrinsic musculature are used. Morphological examinations reveal that the axial skeleton and extrinsic musculature in P5-swimming crabs are more diverse than previously thought, with the exception of the P5 anterior coxa muscle, which originates at the median plate in all P5-swimmers. Ancestral state reconstructions based on parsimony reveal that the stem species of Portunoidea already showed the morphotype of a P5-swimming crab, but with a long merus which probably resulted in less effective P5-swimming than in extant P5-swimming crab species with a short merus. Several other extant taxa represent a reversal of the P5-swimmer morphotype to varying degrees, with some extant species showing a complete reversal of unambiguous P5-swimming crab character states—one example being the well-known common shore crab Carcinus maenas. The absence of a connection between interosternite 7/8 and the sella turcica (the secondary loss of the “brachyuran sella turcica”) in the stem species of Heterotremata, resulting in a junction plate which forms a cavity that offers room and attachment sites for the P5 extrinsic musculature is uncovered as preadaptation to the P5-swimmer morphotype in Heterotremata. This preadaptation is missing in Podotremata and Thoracotremata, the other two traditional main taxa of Brachyura.

Diagnosis and prevalence of two new species of haplosporidians infecting shore crabs Carcinus maenas: Haplosporidium carcini n. sp., and H. cranc n. sp.

This study provides a morphological and phylogenetic characterization of two novel species of the order Haplosporida (Haplosporidium carcini n. sp., and H. cranc n. sp.) infecting the common shore crab Carcinus maenas collected at one location in Swansea Bay, South Wales, UK. Both parasites were observed in the haemolymph, gills and hepatopancreas. The prevalence of clinical infections (i.e. parasites seen directly in fresh haemolymph preparations) was low, at ~1%, whereas subclinical levels, detected by polymerase chain reaction, were slightly higher at ~2%. Although no spores were found in any of the infected crabs examined histologically (n = 334), the morphology of monokaryotic and dikaryotic unicellular stages of the parasites enabled differentiation between the two new species. Phylogenetic analyses of the new species based on the small subunit (SSU) rDNA gene placed H. cranc in a clade of otherwise uncharacterized environmental sequences from marine samples, and H. carcini in a clade with other crustacean-associated lineages.

Effects of an Offshore Wind Farm (OWF) on the Common Shore Crab Carcinus maenas: Tagging Pilot Experiments in the Lillgrund Offshore Wind Farm (Sweden).

Worldwide growth of offshore renewable energy production will provide marine organisms with new hard substrate for colonization in terms of artificial reefs. The artificial reef effect is important when planning offshore installations since it can create habitat enhancement. Wind power is the most advanced technology within offshore renewable energy sources and there is an urgent need to study its impacts on the marine environment. To test the hypothesis that offshore wind power increases the abundance of reef species relative to a reference area, we conduct an experiment on the model species common shore crab (Carcinus maenas).Overall, 3962 crabs were captured, observed, marked and released in 2011 and 1995 crabs in 2012. Additionally, carapace size, sex distribution, color morphs and body condition was recorded from captured crabs. We observed very low recapture rates at all sites during both years which made evaluating differences in population sizes very difficult. However, we were able to estimate population densities from the capture record for all three sites. There was no obvious artificial reef effect in the Lillgrund wind farm, but a spill-over effect to nearby habitats cannot be excluded. We could not find any effect of the wind farm on either, morphs, sex distribution or condition of the common shore crab. Our study found no evidence that Lillgrund wind farm has a negative effect on populations of the common shore crab. This study provides the first quantitative and experimental data on the common shore crab in relation to offshore wind farms.

Susceptibility to Predation Affects Trait-Mediated Indirect Interactions by Reversing Interspecific Competition

Numerous studies indicate that the behavioral responses of prey to the presence of predators can have an important role in structuring assemblages through trait-mediated indirect interactions. Few studies, however, have addressed how relative susceptibility to predation influences such interactions. Here we examine the effect of chemical cues from the common shore crab Carcinus maenas on the foraging behavior of two common intertidal gastropod molluscs. Of the two model consumers studied, Littorina littorea is morphologically more vulnerable to crab predation than Gibbula umbilicalis, and it exhibited greater competitive ability in the absence of predation threat. However, Littorina demonstrated a greater anti-predator response when experimentally exposed to predation cues, resulting in a lower level of foraging. This reversed the competitive interaction, allowing Gibbula substantially increased access to shared resources. Our results demonstrate that the susceptibility of consumers to predation can influence species interactions, and suggest that inter-specific differences in trait-mediated indirect interactions are another mechanism through which non-consumptive predator effects may influence trophic interactions.

Physicochemistry or physiology: cadmium uptake and effects of salinity and osmolality in three crabs of different ecologies

The effects of salinity and osmolality differences on the uptake rates of dissolved cadmium were investigated in 3 crabs of different ecologies — the euryhaline common shore crab Carcinus maenas, the extremely euryhaline Chinese mitten crab Eriocheir sinensis, and a more stenohaline crab, the velvet swimming crab Necora puber. This study tests predictions derived from the interpretations of the authors from a study of Zn uptake by the same crabs, in terms of the balance between physicochemical and counteractive physiological effects controlling trace metal uptake rates from solution. As predicted, reduced salinities caused increases in the cadmium uptake rate of E. sinensis as expected from the free metal ion model, with increased free cadmium ion availabilities in conditions of reduced chloride complexation. In the cases of C. maenas and N. puber, however, decreased salinity was associated with reduced cadmium uptake, a result interpreted in terms of a physiological response by these crabs to low salinity offsetting the physicochemical effect of increased free cadmium ion availability. This physiological response may include reductions in apparent water permeability with reduced salinities. Osmolality experiments showed that the physiological responses made by the crabs to decreases in salinity could not be explained simply by responses to changes in osmotic pressure of the medium. The interaction of physiology and physico- chemistry controls rates of trace metal uptake from solution by these ecophysiologically distinct crab species.

Physical forcing of onshore transport of crab megalopae in the northern Portuguese upwelling system

Wind-driven circulation is a mechanism that may be involved in the shoreward transport of invertebrate larvae. This study investigated the temporal variability of the supply of crab megalopae to an estuary located in the northwest coast of Portugal, which is affected by seasonal upwelling, and related variations in supply to several upwelling indices. Megalopae of the European common shore crab Carcinus maenas (L.). were collected daily, using artificial settlement substrates, during a 3-month period, from March 15 to June 15, 2000. Two settlement episodes were detected, which were consistent with the variation in abundance and size of juvenile crabs. Variations in subtidal sea level and sea surface temperature anomaly were correlated with the strength of along-shore wind stress and consistent with upwelling theory. Contingency analyses showed positive significant associations between increasing intensity of southerly winds and megalopal supply, for time lags of 0–6 d, indicating that shoreward transport occurred during relaxation or reversal of upwelling favourable winds. Associations between megalopal supply and tidal range or the duration of nocturnal flood were not detected. Compared to other studies of the supply of crab megalopae to coastal habitats that used a similar methodology, very low numbers of megalopae were collected during this study. The paucity of C. maenas megalopae in the Ria de Aveiro is in agreement with the low densities of this larval stage in the plankton, and indicates that maintenance of the population is achieved despite a low supply of megalopae.

A New Alien Crab in Europe: Hemigrapsus Sanguineus (Decapoda: Brachyura: Grapsidae)

Abstract The Asian shore crab Hemigrapsus sanguineus is recorded for the first time in two European localities, Le Havre in France and the former estuary “Oosterschelde” in the Netherlands. While breeding populations occur in the former, only two male specimens were found in the latter. In both places, this alien species was mixed with the common shore crab Carcinus maenas.

Effects of changes in salinity and osmolality on the rate of uptake of zinc by three crabs of different ecologies

The effects of salinity and osmolality differences on the uptake rates of dissolved zinc were investigated in 3 crabs of different ecologies —the euryhaline common shore crab Carcinus maenas, the extremely euryhaline Chinese mitten crab Eriocheir sinensis, and a more stenohaline marine crab, the velvet swimming crab Necora puber. Reduced salinities caused increases in the zinc uptake rate of E. sinensis as expected from the free metal ion model, with increased free zinc ion availabilities in conditions of reduced chloride complexation. In the cases of C. maenas and N. puber, however, reduced salinity was associated with reduced zinc uptake, a result interpreted in terms of a physiological response by these crabs to low salinity offsetting the physicochemical effect of increased free zinc ion availability. Results can be partly explained by reported changes in apparent water permeability (AWP) made by the crabs to low salinity, although experiments manipulating solution osmotic pressures independently of salinity (and therefore chloride concentrations) indicate that other physiological responses may also be coming into effect. The interaction of physiology and physicochemistry in controlling trace metal uptake from solution clearly varies between species.

Differing sensitivities of respiratory and osmoregulatory gill tissue of Carcinus maenas (Crustacea: Decapoda) to water-borne copper

Following a 14 d exposure to sublethal concentrations of copper [0 (= control), 50, 100, 200, 300, 500 μg l−1] in a static laboratory system, Gills 5 and 8 of the common shore crab Carcinus maenas (L.) were removed and examined for damage by transmission electron microscopy. In this species, the anterior gills (1 to 6) are primarily respiratory in function, while the posterior gills (7 to 9) have an additional osmoregulatory role, with the respiratory epithelia being restricted to areas proximal to the marginal canal. The first signs of damage (epithelial hyperplasia, necrosis, vacuolation, haemocyte infiltration) occurred at 100 μg Cu l−1, but only in the respiratory gill (5) and only in areas close to the marginal canal. At 200 to 500 μg Cu l−1, these ultrastructural changes spread progressively throughout the lamellae of the respiratory gill. No damage was observed in the osmoregulatory gill (8) until 300 μg Cu l−1, and structural disruption, similar to that seen in the respiratory gill at 100 μg Cu l−1, was not observed until exposure to 500 μg Cu l−1; lipofuscin granule formation was seen in the osmoregulatory gill following exposure to 300 and 500 μg Cu l−1. The physiological implications of the differing sensitivities of the two gill types to water-borne copper are discussed.

Endogenous tidal rhythms of vertical migration in field collected zoea-1 larvae of the shore crab Carcinus maenas:implications for ebb tide offshore dispersal

Employing a highly sensitive infra-red light actography system, circatidal rhythms of vertical migration were recorded in first stage zoea larvae of the common shore crab Carcinus maenas (L.), freshly collected from coastal waters. The rhythms persisted in constant conditions in the laboratory for several days, ascent occurring at the times of expected ebb tides at collection sites, and descent during expected flood tides. Timing was identical in larvae sampled at different stage of spring/neap cycle and from sites where different hydrodynamic conditions prevail. These experiments, supported by repeated surface plankton samples which confirmed that zoea-1 larvae of C. maenas were most abundant at the surface during ebb tides, suggest that the vertical migration behaviour might be linked with avoidance of stranding and offshore dispersal of newly released larvae. The fact that tidal migration rhythm was exhibited by larvae collected from different sites implies that the behaviour is probably widespread for the species. So far, endogenous tidal rhythms of vertical migration in plankton have been demonstrated solely in a few estuarine forms, and have been interpreted only as estuarine retention or reinvasion mechanisms. Present results appear to be the first to demonstrate that endogenous tidal rhythms also exist in the planktonic larvae of a coastal invertebrate and suggest that these larvae may have an adaptive mechanism to avoid stranding and enhance offshore dispersal in the open sea.

Effect of copper on the ultrastructure of the gill epithelium of Carcinus maenas (decapoda: Brachyura)

The epithelial layer of posterior gill number 8 of the common shore crab Carcinus maenas (L.) is made up of three cell types (striated, chief and pillar). Striated cells, with an extensive network of apical and basal infoldings and large numbers of mitochondria, are implicated in ionic regulation. Chief cells contain less plasma membrane infoldings than striated cells, but have a large surface area to volume ratio, implying a predominant role in respiratory gas exchange. The ultrastructural features of pillar cells resemble those of the surrounding epithelial cell type. Thus, pillar cells may play a role in ionic regulation or respiratory gas exchange; however, pillar cells contain a well developed microtubular network, suggesting they also aid structural support and the flow of haemolymph through the gill lamellae. A sublethal copper concentration (50 μg l −1) administered at 35‰ and 10‰ salinity in a flow-through system caused extensive ultrastructural alteration to the gill epithelial cells, including a decrease in the number of plasma membrane infoldings (and associated mitochondria); extensive vacuolation; a change in ribosomal distribution; and disruption of the microtubular network. The extent of the changes was greater at 35‰ than at 10‰ salinity. This paper describes these gill effects in detail, and correlates the ultrastructural changes to previously documented physiological responses of crustaceans exposed to sublethal copper concentrations.

Ecdysteroids fromPycnogonum litorale (Arthropoda, Pantopoda) act as chemical defense againstCarcinus maenas (Crustacea, Decapoda)

Pycnogonum litorale (Ström) is unpalatable to the common shore crabCarcinus maenas, a generalist predator in the pycnogonid's habitat. A feeding bioassay reveals that the crabs are deterred by ecdysteroids that occur in high levels in all developmental stages ofP. litorale. The total ecdysteroids in the pycnogonids reach 5.9×10(-4) M. The 20-hydroxyecdysone 22-acetate (20E22A), which is the predominant ecdysteroid in the pycnogonids, and 20-hydroxyecdysone (20E), the arthropod molting hormone, were tested for their antifeedant effect onC. maenas. When contained in food pellets in homogeneous concentrations, 20E and 20E22A significantly reduced food consumption at 1.25×10(-4) and 5.0×10(-4) molar levels, respectively. The present results demonstrate for the first time chemical defense in arthropods in a marine predator-prey relationship. Furthermore, they provide evidence that ES contained in one animal can act as feeding deterrents on another animal.

Defensive Secretion of Ecdysteroids in Pycnogonum litorale (Arthropoda, Pantopoda)

Abstract In response to disturbance, the pycnogonid Pycnogonum litorale discharges a mixture of eight ecdysteroids (ES). Repeated intensive molestation causes 99% secretion of the endogenous ES present. The concentration of the total ES in the defensive effluent is 1.0 × 10-3 mol · 1-1. 20-Hydroxyecdysone 22-acetate, the predominant ES, reaches 0.8 × 10-3 mol · 1-1. This is sufficient to deter significantly feeding by the common shore crab Carcinus maenas, a generalist predator in the habitat of the pycnogonid. There is evidence that the secreted ES of P. litorale contribute to its unpalatability. The present paper describes for the first time defensive secretion in marine arthropods.

Intraspecific morphological variation related to the moult‐cycle in colour forms of the shore crab Carcinus maenas

The common shore crab Carcinus maenas exhibits a range of carapace colours from green through orange to red, green forms showing some differences of distribution from red/orange forms. To test the hypothesis that colour differences were moult-related, large numbers of Carcinus were collected intertidally and subtidally in summer when moulting is most prevalent, and their moult stages determined. Red and orange coloration was found only to occur in the larger size classes in crabs in prolonged intermoult, but not solely in the largest crabs in terminal anecdysis. Red crabs were characterized by a heavier load of epibionts and a strong, thicker carapace. In contrast, green crabs were found over the entire size range and appeared to be actively moulting forms; they carried fewer epibionts and had a thinner integument than red forms. The significance of morphological differences between red/orange and green forms of Carcinus maenas is considered in relation to previously reported behavioural, physiological and ecological differences between the colour forms.

Larval and postlarval growth of individually reared specimens of the common shore crab Carcinus maenas (L.)

Specimens of Carcinus maenas (L.) from the Isle of Man were reared individually at 15 and 20 °C under controlled conditions from hatching to the puberty moult. Survival was monitored and for every specimen the size and duration of each instar was recorded. Survival with time was better at 15 ° C but survival to a given instar was higher at 20 ° C. Survival was generally good, until heavy mortality followed the puberty moult. The puberty moult was consistently the 11th postlarval moult at 15 °C and the 12th at 20 ° C. The intermoult period was shorter at the higher temperature and the growth rate higher. The moult increment was slightly larger at 15 °C, so following the puberty moult specimens were larger than at 20 °C, despite having had one fewer moult. The coefficient of variation in size did not increase through the sequence of larval instars but increased steadily through the postlarval sequence.

Variations of hemolymph proteins of the common shore crab Carcinus maenas after a bacterial infection

The influence of a bacterial infection in Carcinus maenas both generally and with specific respect to hemolymph proteins is described. The infection shows severe effects upon the moulting cycle and general activity. The total protein concentration remains constant. Qualitative and quantitative differences between healthy and infected crabs appear, however, after electrophoretical separation (Disc-PAGE), indicating the importance of this method as an analytical tool in animal disease research. The protein pattern of the diseased crabs shows two new protein components. The origin of these additional fractions is discussed. Moreover, the levels of most other proteins, which are identified as hemocyanin subunits and a nonrespiratory protein, are higher in diseased crabs, thus indicating an elevated metabolic rate.

A bacterial infection in the common shore crab Carcinus maenas and the fiddler crab Uca pugilator

A bacterial infection in Carcinus maenas and in Uca pugilator is described. The percentage of infections recorded in the field was between 0 and 10%, depending on season. Infected crabs remain about 3 times longer in Intermolt Stages C3 and C4 than do healthy crabs. In infected specimens of both species, the glucose level in the hemolymph is increased and protein, copper and lipid concentrations in the hemolymph as well as the glycogen content of various tissues are diminished. The coagulation process is disturbed in infected crabs. The hemocytes aggregate, but the formation of fibrin-like fibers, which can be observed in healthy crabs, does not occur.

Mechanisms of intracellular isosmotic regulation: Fate of14C-labeled serum proteins in the shore crabCarcinus maenas after changed environmental salinity

1. Two individuals of the common shore crabCarcinus maenas, which had been maintained for 2 months in 11 ‰ S, were injected 100 µCi of14C-glucose and a14C-amino acid mixture in physiological saline during 5 days. They were the source of a14C-labeled serum protein, which was injected into the hemocoel of crabs which had been maintained for more than 2 months in 11 ‰ S. Six hours after injection the distribution of label and concentrations of serum proteins and free amino acids were investigated in 13 crabs, transferred to 38 ‰ S after the injection, and in 13 crabs (controls) which remained in 11 ‰ S. 2. In crabs transferred from 11 to 38 ‰ S, proteolytic processes in serum increased; this was demonstrated by a decrease in serum proteins 6 hours after transfer. This assumption is confirmed by the fact, that14C-radioactivity in serum originating from serum proteins decreased by 44.4 % within 6 hours after transfer, whereas in controls it decreased by 32.6 %. 3. Serum proteins have been metabolized in favour of low molecular intracellular intermediary products, such as amino acids, sugars, and organic acids, all contributing to the new intracellular osmotic pressure. This is shown by a significant increase in radioactivity of low molecular intracellular intermediary products.