European Shore Crab Carcinus Maenas Research Articles

Artificial rockpools create habitat refugia on seawalls at high tide

Rockpools are fundamental habitats on natural rocky shores that provide refugia for marine life at low and high tide. Yet, artificial coastal structures lack the topographical complexity seen in these natural habitats. Eco-engineering, that may include the deployment of artificial rockpools, attempts to address the lack of suitable habitat on coastal infrastructure but most studies focus on species abundance metrics at low tide. It is important to understand how eco-engineering interventions may provide habitat at high tide compared to the surrounding artificial substrate.In this study, we demonstrate how groups of rockpools (1, 3 or 5 rockpools) add habitat complexity at high tide to a concrete seawall in Poole Harbour, UK. Between April and October 2022, eighteen GoPro cameras were deployed to record species richness and abundance in artificial rockpools and the adjacent concrete sea wall. Additionally, the length of time the most abundant fauna (the shanny fish Lipophrys pholis and the European shore crab Carcinus maenas) spent engaging in different behaviour (resting, feeding, moving) was recorded.Overall, there was no significant difference in the abundance and species richness of mobile fauna using the artificial rockpools versus the seawall. However, both the shanny and shore crab generally spent more time in the rockpools than on the seawall. Both crabs and shanny preferentially engaged in feeding behaviours on the seawall, which has been attributed to the high percentage cover of barnacle prey. Crabs and shanny spent more time resting in the rockpools than the seawall and the only reproductive behaviour observed occurred within the rockpools. Our work suggests that artificial rockpools support the habitat needs and multiple life history requirements of these species at high tide. Both the seawall and rockpools provide valuable resources, which further emphasises the need for variety in eco-engineering feature designs.

On their way to the north: larval performance of Hemigrapsus sanguineus invasive on the European coast—a comparison with the native European population of Carcinus maenas

The Asian shore crab Hemigrapsus sanguineus has become invasive in North Europe and it co-occurs and competes with the native European shore crab Carcinus maenas. Both species develop through a feeding and dispersive larval phase characterised by several zoeal and a settling megalopa stage. Larvae of marine crabs are vulnerable to food limitation and warming has the potential to exacerbate the negative effects of food limitation on survival and growth. We quantified the combined effects of temperature and food limitation on larval performance (survival and growth) of H. sanguineus and we compared our results with those reported on performance of C. maenas larvae, under the same experimental design and methodology. Larvae from four females of H. sanguineus collected on Helgoland (North Sea) were experimentally reared from hatching to megalopa, at four temperatures (range 15–24 °C) and two food conditions (permanent vs. daily limited access to food). Larval survival of H. sanguineus was low at 15 °C and increased with temperature, in contrast to the high survival reported for C. maenas larvae in the range 15–24 °C. Food limitation reduced survival and body mass of H. sanguineus larvae at all temperatures, but without evidence of the exacerbating effect caused by high temperatures and reported for C. maenas. By contrast, high temperature (24 °C) mitigated the negative effect of food limitation on body mass on H. sanguineus larvae. Advantages of H. sanguineus over C. maenas appear especially under the increased temperatures expected from climate change.

Resistance to white spot syndrome virus in the European shore crab is associated with suppressed virion trafficking and heightened immune responses.

All decapod crustaceans are considered potentially susceptible to White Spot Syndrome Virus (WSSV) infection, but the degree of White Spot Disease (WSD) susceptibility varies widely between species. The European shore crab Carcinus maenas can be infected with the virus for long periods of time without signs of disease. Given the high mortality rate of susceptible species, the differential susceptibility of these resistant hosts offers an opportunity to investigate mechanisms of disease resistance. Here, the temporal transcriptional responses (mRNA and miRNA) of C. maenas following WSSV injection were analysed and compared to a previously published dataset for the highly WSSV susceptible Penaeus vannamei to identify key genes, processes and pathways contributing to increased WSD resistance. We show that, in contrast to P. vannamei, the transcriptional response during the first 2 days following WSSV injection in C. maenas is limited. During the later time points (7 days onwards), two groups of crabs were identified, a recalcitrant group where no replication of the virus occurred, and a group where significant viral replication occurred, with the transcriptional profiles of the latter group resembling those of WSSV-susceptible species. We identify key differences in the molecular responses of these groups to WSSV injection. We propose that increased WSD resistance in C. maenas may result from impaired WSSV endocytosis due to the inhibition of internal vesicle budding by dynamin-1, and a delay in movement to the nucleus caused by the downregulation of cytoskeletal transcripts required for WSSV cytoskeleton docking, during early stages of the infection. This response allows resistant hosts greater time to fine-tune immune responses associated with miRNA expression, apoptosis and the melanisation cascade to defend against, and clear, invading WSSV. These findings suggest that the initial stages of infection are key to resistance to WSSV in the crab and highlight possible pathways that could be targeted in farmed crustacean to enhance resistance to WSD.

X-Ray Microscopy of the Larval Crustacean Brain.

Micro-computed X-ray tomography (μCT) coupled with visualization techniques such as three-dimensional reconstruction of internal morphological structures has opened up new pathways for analyzing the anatomy of nervous systems in intact specimens. The possibility for combining μCT with other techniques is one of the major advantages of μCT scanning, and the technical development of higher resolutions in lab-based μCT-scanners allows for investigating the anatomy of specimens in the sub-milimeter range. The European shore crab Carcinus maenas features a larval development over four zoeal and one megalopal stage with body lengths ranging from 500μm to 2000μm. The developing nervous system in the larvae of C. maenas is organized into a central brain which is connected via esophageal connectives with a ventral nerve chord and segmental ganglia. Since soft tissues such as the nervous tissues feature low contrasts compared to other tissues such as muscles or cuticularized body parts, the interpretation in μCT scans is challenging and needs some practice. The protocol described here is also applicable for larger specimens of a variety of species and spans over 2-3days resulting in an image stack ready for postprocessing and visualization.

An atlas of larval organogenesis in the European shore crab Carcinus maenas L. (Decapoda, Brachyura, Portunidae)

BackgroundThe life history stages of brachyuran crustaceans include pelagic larvae of the Zoea type which grow by a series of moults from one instar to the next. Zoeae actively feed and possess a wide range of organ systems necessary for autonomously developing in the plankton. They also display a rich behavioural repertoire that allows for responses to variations in environmental key factors such as light, hydrostatic pressure, tidal currents, and temperature. Brachyuran larvae have served as distinguished models in the field of Ecological Developmental Biology fostering our understanding of diverse ecophysiological aspects such as phenotypic plasticity, carry-over effects on life-history traits, and adaptive mechanisms that enhance tolerance to fluctuations in environmental abiotic factors. In order to link such studies to the level of tissues and organs, this report analyses the internal anatomy of laboratory-reared larvae of the European shore crab Carcinus maenas. This species has a native distribution extending across most European waters and has attracted attention because it has invaded five temperate geographic regions outside of its native range and therefore can serve as a model to analyse thermal tolerance of species affected by rising sea temperatures as an effect of climate change.ResultsHere, we used X-ray micro-computed tomography combined with 3D reconstruction to describe organogenesis in brachyuran larvae. We provide a detailed atlas of the larval internal organization to complement existing descriptions of its external morphology. In a multimethodological approach, we also used cuticular autofluorescence and classical histology to analyse the anatomy of selected organ systems.ConclusionsMuch of our fascination for the anatomy of brachyuran larvae stems from the opportunity to observe a complex organism on a single microscopic slide and the realization that the entire decapod crustacean bauplan unfolds from organ anlagen compressed into a miniature organism in the sub-millimetre range. The combination of imaging techniques used in the present study provides novel insights into the bewildering diversity of organ systems that brachyuran larvae possess. Our analysis may serve as a basis for future studies bridging the fields of evolutionary developmental biology and ecological developmental biology.

Reassessing the invasion of South African waters by the European shore-crab Carcinus maenas

The European shore-crab Carcinus maenas has been present in South Africa since 1983. Despite this species’ international reputation as a biological invader, its distribution in this region has only been considered by three outdated ‘snapshot surveys.’ The present study is the most comprehensive to date, providing an update on the species’ range and the first temporal assessment of its abundance and demographics. Along South Africa's Cape Peninsula and surrounding areas, C. maenas was absent from 12 intertidal sites surveyed, except for Sea Point, and no crabs were found during subtidal surveys along the open coastline. Subtidal harbour populations were recorded in the Cape Town harbours of Table Bay and Hout Bay (previously estimated as comprising approximately 164 200 and 6 500 individuals, respectively). Table Bay was surveyed monthly for one year, using baited traps, crab condos and postlarvae settlement collectors, to assess size distributions and reproductive seasonality of the crab. Reproductive females were recorded throughout most of the year. These results suggest that the harbour populations could be targeted by control programmes, but provide no strong evidence to support the initiation of management action during a particular season. The lack of detection of postlarval settlement, even among well-established populations, suggests this will not be a useful monitoring tool for detecting incursions.

Genetic structure of Carcinus maenas in southeast Australia

The European shore crab Carcinus maenas is a highly successful marine invader, and has displayed rapid range expansion following its introduction to many parts of the world. In Australia, it was first reported in Port Phillip Bay, Victoria in the late 1800s. Despite predictions that it would expand its range northward, its distribution has remained limited to the southeast coast of the mainland and to Tasmania. Using microsatellite loci and mitochondrial DNA, we assessed whether low connectivity among southeastern Australian estuaries might be contribut- ing to the limited distribution of this invasive species. Under this hypothesis, we expected that sampling of C. maenas from 6 estuaries, roughly evenly spaced along the southeast coast, would reveal: (1) greater genetic variability among than within estuaries; (2) increasing genetic dissimi- larity with distance from Port Phillip Bay; and (3) in the absence of human-mediated dispersal, declining genetic variation with distance from Port Phillip Bay. Contrary to these predictions, we found that genetic variability was no greater among than within mainland southeast Australian estuaries — indicating significant gene flow. Some slight genetic differentiation was, however, evident between Tasmania and the mainland. Multiple introductions appear to have contributed to the Australian population. The high connectivity of populations among southeast Australian estuaries suggest that management strategies focused on eradication of C. maenas from individ- ual localities will not be effective. Factors other than limited connectivity appear to be responsible for the slow range expansion up the east Australian coast.

Competition and niche segregation following the arrival of Hemigrapsus takanoi in the formerly Carcinus maenas dominated Dutch delta

In a combined study including a 20year monitoring programme of the benthic communities of four Dutch delta waters and a snapshot survey conducted in the Oosterschelde tidal bay in 2011, the populations of the native portunid European shore crab Carcinus maenas and the introduced varunid crabs Hemigrapsus takanoi and Hemigrapsus sanguineus were investigated. Whereas C. maenas was the most common shore crab in these waters, its numbers have declined on the soft sediment substrates during the last 20years. As the two exotic crab species were first recorded in the Dutch delta in 1999, they could not have initiated the decline of the native C. maenas. However, within a few years H. takanoi completely dominated the intertidal hard substrate environments; the same environments on which juvenile C. maenas depend. On soft sediment substrate the native and exotic shore crab species are presently more or less equally abundant. H. takanoi might initially have taken advantage of the fact that C. maenas numbers were declining. Additionally H. takanoi are thriving in expanding oyster reefs of Crassostrea gigas (Pacific oyster) in the Dutch delta waters, which provide new habitat. Nowadays H. takanoi appears to be a fierce interference competitor or predator for small C. maenas specimens by expelling them from their shelters. These interactions have led to increased mortality of juvenile C. maenas. At present the C. maenas populations seem to be maintained by crabs that survive and reproduce on available soft sediment habitats where H. takanoi densities are low.

Comparative brain architecture of the European shore crab Carcinus maenas (Brachyura) and the common hermit crab Pagurus bernhardus (Anomura) with notes on other marine hermit crabs

The European shore crab Carcinus maenas and the common hermit crab Pagurus bernhardus are members of the sister taxa Brachyura and Anomura (together forming the taxon Meiura) respectively. Both species share similar coastal marine habitats and thus are confronted with similar environmental conditions. This study sets out to explore variations of general brain architecture of species that live in seemingly similar habitats but belong to different major malacostracan taxa and to understand possible differences of sensory systems and related brain compartments. We examined the brains of Carcinus maenas, Pagurus bernhardus, and three other hermit crab species with immunohistochemistry against tyrosinated tubulin, f-actin, synaptic proteins, RF-amides and allatostatin. Our comparison showed that their optic neuropils within the eyestalks display strong resemblance in gross morphology as well as in detailed organization, suggesting a rather similar potential of processing visual input. Besides the well-developed visual system, the olfactory neuropils are distinct components in the brain of both C. maenas and P. bernhardus as well as the other hermit crabs, suggesting that close integration of olfactory and visual information may be useful in turbid marine environments with low visibility, as is typical for many habitats such as, e.g., the Baltic and the North Sea. Comparing the shape of the olfactory glomeruli in the anomurans showed some variations, ranging from a wedge shape to an elongate morphology. Furthermore, the tritocerebrum and the organization of the second antennae associated with the tritocerebrum seem to differ markedly in C. maenas and P. bernhardus, indicating better mechanosensory abilities in the latter close to those of other Decapoda with long second antennae, such as Astacida, Homarida, or Achelata. This aspect may also represent an adaptation to the "hermit lifestyle" in which competition for shells is a major aspect of their life history. The shore crab C. maenas, on the other hand seems to rely much less on mechanosensory information mediated by the second antennae but in water, the visual and the olfactory senses seem to be the most important modalities.

Milky hemolymph syndrome (MHS) in spiny lobsters, penaeid shrimp and crabs

Black tiger shrimp Penaeus monodon, European shore crab Carcinus maenas and spiny lobster Panulirus spp. can be affected by milky hemolymph syndrome (MHS). Four rickettsia-like bacteria (RLB) isolates of MHS originating from 5 geographical areas have been identified to date. The histopathology of the disease was characterized and a multiplex PCR assay was developed for detection of the 4 bacterial isolates. The 16S rRNA gene and 16-23S rRNA intergenic spacer region (ISR) were used to examine the phylogeny of the MHS isolates. Although the pathology of this disease appears similar in the various different hosts, sequencing and examination of the phylogenetic relationships reveal 4 distinct RLB involved in the infection process.

Interspecific activity of the sex pheromone of the European shore crab (Carcinus maenas)

The recent identification of uridine diphosphate (UDP) as the female sex-pheromone in the European shore crab Carcinus maenas demonstrated not only the link between moult and pheromone production, but also how it may have evolved from a ‘simple’ metabolic byproduct. Consequently, it is expected to be present in other moulting crustaceans, thus raising issues involving species specificity of the female pheromone. Bioassays were conducted using synthetic pheromone (UDP, 10 –3 –10 –4 M) to examine if it induced sexual behaviour in other crustacean species that are neither closely related nor occur in the same ecosystem. The snow crab, Chionoecetes opilio , and the yellowline arrow crab, Stenorhynchus seticornis , both belonging to a different superfamily (Majoidea) and occurring in different habitats than C. maneas (Portunoidea), displayed significant sexual behaviour towards UDP treated objects ( p < 0.005). These and other examples demonstrate that the female sex-pheromone UDP is not species-specific but is present and active in some other decapod crustaceans.

Seasonal fluctuations of tissue mercury contents in the European shore crab Carcinus maenas from low and high contamination areas (Ria de Aveiro, Portugal)

The main objective was to study the seasonal variation of mercury concentrations in different tissues (muscle, hepatopancreas and gills) of Carcinus maenas from low and high Hg contaminated areas, a valuable resource in temperate estuaries and a possible pathway for human uptake. Individuals of two size classes (around 35 and 55 mm cephalothorax wide) were captured monthly between March 1999 and May 2000 in two areas of Ria de Aveiro: in the main navigation channel that connects the lagoon to the sea, and in the inner lagoon area heavily contaminated by mercury (maximum Hg in sediments of 5.4 μg g −1). Pronounced decreases in salinity and temperature and reduced food availability in winter seemed to be the responsible for the decline of the crab condition index (0.75–0.45) in larger individuals. Muscle and hepatopancreas exhibited higher mercury concentrations than gills, with concentrations in the contaminated site ranging from 0.03 to 0.63 μg g −1 and 0.02 to 0.34 μg g −1, respectively. Linear regressions between muscle and hepatopancreas ( r = 0.94, p < 0.001) and muscle and gills ( r = 0.97, p < 0.001) suggested a rapid redistribution of mercury inside the organism. During winter, a rapid elimination of mercury was found in the three analysed tissues followed by uptake. Larger crabs presented elimination rates from 18 to 34 ng g −1 per week, while the smaller crabs showed lower elimination rates (10–24 ng g −1 per week). The uptake was similar in both size classes (11–15 ng g −1 and 8.1–15 ng g −1 per week, respectively for large and small crabs). Our results suggest that C. maenas harvested in the contaminated areas must be considered with caution, since Hg concentrations were found to exceed the threshold concentration allowed for human consumption (0.5 μg g −1).

Primer and Short-Range Releaser Pheromone Properties of Premolt Female Urine from the Shore Crab Carcinus maenas

The European shore crab Carcinus maenas is considered to rely on a female pheromone when mating. Evidence, however, is scarce on how the urine pheromone in itself affects males. We investigated male primer and releaser responses to female pheromones with methods that minimized effects from females, delivering female urine either as a pump-generated plume or deposited on a polyurethane sponge. We delivered the pheromone at different concentrations in far, near, and close/contact range to get a picture of how distance affects behavioral response. Our results show that substances in premolt female urine (PMU) function as primer and potent short-range releaser pheromones. Based on the olfactometer and sponge tests, we conclude that PMU stimulus in itself is sufficient to elicit increased search and mating-specific behaviors such as posing, posing search, cradle carrying, and stroking. Pheromone concentrations do not seem to be important for attenuating search and posing as long as the level is above a certain threshold concentration. Instead, pheromone levels seem to play a role in male acceptance of females, recruiting more males to respond, and generating better responses with increasing concentration.

Mechanosensory properties of the mouthpart setae of the European shore crab Carcinus maenas

In decapod crustaceans, the largest density and diversity of sensilla, referred to as setae, is in general found on the mouthparts, but little is known about their sensory properties and thereby their functions. Here data are presented from mechanoreceptors from the two largest mouthparts, maxilliped 2 and 3, of the European shore crab Carcinus maenas. The mechanoreceptors were found to respond to either displacements of the entire seta or bending of the setal shaft. The displacement-sensitive cells encode both the amplitude and the velocity of the displacement and about half were found to be directional but most in a non-exclusive way. The amplitude of the stimulus is encoded in the number of spikes produced with a linear correlation. The velocity is encoded in the interspike intervals with shorter intervals at higher velocities. In the latter case, the correlation follows a power function. The physiological data is correlated with the morphology and usage of the maxillipeds were examined with scanning electron microscopy and macro video recordings respectively. Recordings were obtained from cells associated with four different setal types and they all showed similar mechanosensory properties supporting that the external morphology of setae is more closely connected to their non-sensory functions, e.g., mechanical manipulation of the food items. The details of the sensory properties together with the high setal density, especially on maxilliped 3, suggest that a large amount of tactile information is gathered during feeding.

Range extension of two invasive crab species in eastern Australia: Carcinus maenas (Linnaeus) and Pyromaia tuberculata (Lockington)

Relatively few introduced crabs are presently known from Australian waters. The present report significantly extends the documented range of the European Shore Crab Carcinus maenas (Linnaeus) and the Fire Crab Pyromaia tuberculata (Lockington) in eastern Australia, based on recently collected specimens now deposited in the Australian museum, Sydney (AM), and old collections in the Macleay museum, University of Sydney (MM) (Appendix). Carcinus maenas is well known as an invasive and destructive species (Behrens Yamada, 2001). The species is native to the northeastern Atlantic but is now established in southern Australia, South Africa, the northern Pacific and Atlantic coasts of North America (Carlton and Cohen, 2003). Carcinus maenas was first reported in Australia in 1900 from Port Phillip Bay, Victoria, and is believed to have arrived on hull fouling on ships or amongst discarded, solid, marine ballast (Fulton and Grant, 1902). Owing to the busy shipping trade between European ports and Port Phillip Bay in the 19th century, it is likely that Port Phillip Bay was the original site of introduction (Proctor and Thresher, 1997). Carcinus maenas has since been reported from the Swan River, Western Australia, Gulf St. Vincent and the Coorong, South Australia, eastern Tasmania and Port Phillip Bay, Victoria, to Narooma, southern New South Wales (Furlani, 1996; Proctor and Thresher, 1997) (Fig. 1(A)). The present new eastern Australian records of C. maenas from Jervis Bay, Lake Conjola, and the Sydney area extend the documented range in New South Wales from Nangudga Lake, near Narooma (36°15'S), northwards by almost 300 km. Aside from the listed specimens, C. maenas was also sighted in the littoral zpne by the present author at the following localities on the