Carcinus Maenas Research Articles

Role of native and invasive non-native marine invertebrate species as carriers for pathogens Vibrio spp. and ostreid herpesvirus-1 µVar

Invasive non-native species (INNS) are expanding their geographic range due to climate change, maritime traffic (primary route) and aquaculture (secondary route), resulting in the potential spread of microbes associated with them. Few studies have investigated the INNS-pathogen phenomenon. In this study, marine invertebrate species (native and INNS) were sampled monthly over 3 mo and screened by PCR for the ostreid herpesvirus-1 microvariant (OsHV-1 μVar) and Vibrio bacteria. Both pathogens are negatively associated with bivalve aquaculture. Sample sites included a shipping port, an oyster farm, a marsh nature reserve and a riverine site. Crustacea, Mollusca, Polychaeta, Tunicata and Porifera were sampled. Vibrio spp. were detected in 54.3% (n = 319/588) across all taxa and sample sites. The first detection of V. salmonicida associated with Atlantic salmon Salmo salar was detected in the INNS beaked barnacle Austrominius modestus. OsHV-1 μVar (7.7%, 45/588) was detected in Crustacea, Mollusca and Polychaeta at non-culture sites and in mussels Mytilus spp. at a much lower temperature (average sea surface temperature, SST, 11.25°C) than previously recorded. The shipping port had the highest Vibrio diversity and OsHV-1 μVar detection. Over half (51.1%) of ‘recently dead’ shore crabs Carcinus maenas had either pathogen detected compared to 29.4% of living crabs. OsHV-1 μVar detection was significantly higher in dead crabs (24.4%) compared to living crabs (5.9%). Findings from this study contribute a better understanding of the role of estuarine native and INNS as vectors/carriers of pathogens and of how the spread of INNS might facilitate the spread of pathogens.

Chemical profiling of surface water and biota in protected marine harbours impacted by combined sewer overflows.

Chemical profiling of surface water and biota in protected marine harbours impacted by combined sewer overflows.

Impacts of the invasive blue crab Callinectes sapidus on small-scale fisheries in a Mediterranean lagoon using fishery landing data.

Human activities have introduced numerous non-native species beyond their natural habitats, leading to their establishment in new regions. Among them, the Atlantic blue crab (Callinectes sapidus) has significantly impacted biodiversity and fisheries in the Mediterranean Sea. This study investigates the recent population increase of C. sapidus associated changes of small-scale fisheries in one Mediterranean lagoon, the Sacca di Goro lagoon within the Po River Delta. We analysed the influence of environmental factors and C. sapidus biomass on trends in landings of commercially important species, using multivariate analysis, including principal component analysis (PCA) and redundancy analysis (RDA), as well as variance partitioning, linear regression and change point analysis on fishery landings data. Our results suggest that the spread of C. sapidus coincides with a decline in several commercial species, such as the European flounder (Platichthys flesus), the big-scale sand smelt (Atherina boyeri), the European eel (Anguilla anguilla) and the Mediterranean green crab (Carcinus aestuarii), suggesting a strong ecological and economic impacts of the blue crab invasion. The main mechanisms by which C. sapidus could drive this trend likely involve predation and competition, although further investigation is needed for confirmation. Annually averaged environmental variables (i.e., water temperature, salinity, nitrate and chlorophyll-a concentrations) were not significant predictors of commercial species trends, suggesting that the changes in landings cannot be primarily attributed to environmental factors. This study is the first to provide a comprehensive analysis of the potential effects of C. sapidus on the relative abundance of key fisheries species in Mediterranean Sea, suggesting a potential link between the rapid increase in its abundance and observed fish landing trends. The results highlight the need for integrated management strategies, including promoting market opportunities for C. sapidus and consideration of ecosystem-based management to control its abundance such as the protection of native local predators.

Tracking two invasions for the cost of one: opportunistically tracking the range expansion of non-native Palaemon macrodactylus in the Salish Sea through participatory science

While conducting early detection monitoring for invasive European green crab (Carcinus maenas), Washington Sea Grant Crab Team discovered a non-native shrimp Palaemon macrodactylus, hitherto unreported along Washington’s portion of the Salish Sea. By examining prior data, and tracking this species closely over subsequent years, we were able to consistently monitor the spread and increase of this species across the region. The program and dataset enabled a highly quality-controlled and verified record of this species. Originating near the Canadian border, P. macrodactylus has spread southward into the main basins of Puget Sound and has been observed in Hood Canal as well. At sites where this shrimp has been consistently documented, the relative abundance over time has increased, indicating that the invasion has become established but not yet reached equilibrium. Similar to studies in other regions of the globe where it is found, we observed that P. macrodactylus favors estuarine habitats and demonstrates seasonal migration within creek systems. The Salish Sea population is within demographic values published for other invasions, but females achieve a smaller maximum size, and reproductive maturity at a smaller size than those reported from the native range. This might suggest the potential for an altered life history strategy favored by introduction to a novel evolutionary context. Given the rate of spread over the last decade, and density of suitable habitat, we anticipate that P. macrodactylus will continue to expand its range within the Salish Sea. No ecological impacts of this species have been documented elsewhere. Nevertheless, this approach demonstrates the benefit of participatory science monitoring in tracking cryptic or otherwise unnoticed species invasions.

Mangrove-associated Pacific oysters (Magallana gigas) influence estuarine biodiversity

Estuarine ecosystems are often characterised by endemic foundation organisms which facilitate ecosystem interactions and processes established over millennia. Introduction of non-native foundation species can significantly alter ecological communities and functions. Here, we assessed the effects of introduced, reef-forming Pacific oyster Magallana gigas, within a temperate Australian mangrove-dominated estuary. Specifically, we investigated whether mangrove-attached M. gigas oyster reefs influenced intertidal fish and invertebrate communities, and fish foraging behaviour. We measured and contrasted the benthic structure and faunal communities of fringing bare sediment, Avicennia marina mangrove and Pacific oyster M. gigas reef habitats using a combination of quadrats, fyke nets and remote unbaited video (RUV) surveys. Pacific oyster reefs showed no impacts on pneumatophore density or morphology, but were positively associated with higher seedling densities. Furthermore, invertebrate and fish community metrics (e.g. richness, biomass, length) were typically higher in M. gigas reefs compared to the other habitats. However, several mobile, non-native species were predominantly detected in M. gigas reefs, including exotic gobies and European shore crabs Carcinus maenas, a declared marine pest. Overall, we found that M. gigas reefs in fringing mangrove forests were associated with biodiverse faunal communities, including fisheries-targeted species, but also facilitated other non-native species. These outcomes highlight some of the ecological pros and cons of non-native oyster reefs and the complexity of managing estuaries globally where Pacific oysters increasingly co-occur with endemic habitat-forming species.

CORRECTION: Larval connectivity for European green crab management in the Salish Sea and surrounding waters

CORRECTION: Larval connectivity for European green crab management in the Salish Sea and surrounding waters

Fatty acid content and DNA concentration of the Mediterranean green crab Carcinus aestuarii’s hepatopancreas in relation to dimethoate acute toxicity

Fatty acid content and DNA concentration of the Mediterranean green crab Carcinus aestuarii’s hepatopancreas in relation to dimethoate acute toxicity

Impact of marine heatwaves on Carcinus maenas crabs: Physiological and biochemical mechanisms of thermal stress resilience.

Impact of marine heatwaves on Carcinus maenas crabs: Physiological and biochemical mechanisms of thermal stress resilience.

Allatostatin-C signaling in the crab Carcinus maenas is implicated in the ecdysis program.

The allatostatin (AST) family of neuropeptides are widespread in arthropods. The multitude of structures and pleiotropic actions reflect the tremendous morphological, physiological and behavioral diversity of the phylum. Regarding the AST-C (with C-terminal PISCF motif) peptides, crustaceans commonly express three (AST-C, AST-CC and AST-CCC) that have likely arisen by gene duplication. However, we know little regarding their physiologically relevant actions. Here, we functionally characterize the cognate receptor for AST-C and AST-CC, determine tissue expression, and comprehensively examine the localization of AST mRNA and peptide. We also measured peptide release, circulating titers and performed bioassays to investigate possible roles. AST-C and AST-CC activate a single receptor (AST-CRd), but this, and other candidate receptors, were not activated by AST-CCC. Whole-mount in situ hybridization and hybridization chain reaction fluorescent in situ hybridization complemented neuropeptide immunolocalization strategies and revealed extensive expression of AST-Cs in the central nervous system. AST-C or AST-CCC expressing neurons were found in the cerebral ganglia, but AST-CC expression was never observed. Of note, we infer that AST-C and AST-CC are co-expressed in every neuron expressing crustacean cardioactive peptide (CCAP) and bursicon (BURS); all four peptides are released from the pericardial organs during a brief period coinciding with completion of emergence. In contrast to other studies, none of the AST-C peptides exhibited any effect on ecdysteroid synthesis or cardiac activity. However, expression of the AST-C receptor on hemocytes suggests a tantalizing glimpse of possible functions in immune modulation following ecdysis, at a time when crustaceans are vulnerable to pathogens.

Morphological and genetic evidence supports that invasive Carcinus Leach, 1814 in South Australia are C. maenas (Linnaeus, 1758)

ABSTRACT Accurate identification of invasive marine species is essential for understanding species range expansions and developing taxon-specific surveillance tools. The globally invasive European green crab Carcinus maenas, and the Mediterranean green crab C. aestuarii, which has a more limited introduced range and is a lesser concern as a pest, can be difficult to distinguish morphologically and can also hybridise. Although the species are visually similar, it has been proposed that they can be distinguished using carapace morphometrics. In temperate South Australia, invasive Carcinus have been reported as C. maenas. This study aimed to confirm the identity of invasive Carcinus in South Australia using carapace morphometrics and mtDNA COI gene sequencing. Carapace width:length ratios of 1,311 Carcinus from South Australia were variable within sexes and corresponded to those of both C. maenas and C. aestuarii. However, COI sequencing of 59 of these crabs revealed ~ 100% sequence matches to C. maenas and diverged from C. aestuarii sequences on GenBank by an average of 11.5%. Results supported that the South Australian population is C. maenas and that intraspecific morphological variation prevents carapace ratios alone from distinguishing species of Carcinus. DNA sequencing should be used to confirm the species identity of crabs identified as Carcinus during new incursions.

The Effects of Combined Stress from pH and Microplastic-Derived Odours on the European Green Crab Carcinus maenas's Olfactory Behaviour.

Ocean acidification (OA) associated with climate change is expected to lower the ocean's pH by 0.5 units by 2100. Whilst associated effects such as coral bleaching and shell calcification are well documented, lesser-known impacts are the 'invisible' effects on animal sensory systems. Olfactory disruption impacts the behaviour towards chemical cues in many marine species, including crustaceans. We examine the effects of microplastic odour and additional stressors on the European green crab C. maenas. Using uridine diphosphate (UDP) and uridine triphosphate (UTP) as a sex pheromone bouquet, glutathione (GSH) as a food cue, and polyethylene (PE) as plastic odour, cues were mixed with carboxycellulose to create slow-release gels. Crabs were exposed to gels in seawater pH values of 8.2, 7.6, and 7.2. Crabs took longer to react to all odours in reduced pH conditions (pH 8.2 to pH 7.2, p = 0.0017). At a low pH, PE-exposed crabs exhibited attraction towards microplastic odour and changed behavioural responses by burying. The study confirms low pH as disruptive to olfaction and highlights that plastic derivatives can become more bioactive at reduced pH levels, potentially increasing the threat posed by microplastic pollution. Further research is required to determine the potential long-term impacts of the combined threat of microplastics and reduced pH in the environment.

Towed Video-Diver: A Useful Low-Cost Tool for Rapid Benthic Mapping and Biodiversity Monitoring

Marine Protected Areas (MPAs) require efficient monitoring tools to assess habitats and biodiversity, particularly in remote or understudied regions. This study demonstrates the utility of the towed video-diver technique combined with high-resolution video for rapidly surveying benthic habitats and associated taxa. Applied in Arredondo, a shallow bay within an MPA in Atlantic Patagonia, the method covered 14,000 m2 through eight transects, utilizing just 180 min of dive time and ~300 min of video analysis. Substrate types and their associated taxa were classified using the CATAMI framework, yielding a list of 28 taxa and density estimates of mobile organisms. Additionally, the percentage cover of Gracilaria sp.—a commercially valuable macroalga historically overexploited in the region—was estimated for the bay. The invasive crab Carcinus maenas was found across all substrate types on the bay, underscoring its ecological tolerance and the need for ongoing monitoring. This cost-effective, rapid methodology is highly effective for detecting and describing areas of ecological or conservation interest, providing critical baseline data for targeted, detailed studies. Its simplicity and efficiency make it ideal for initial surveys in remote regions, supporting the conservation and management of MPAs.

Effects of low temperature exposure and acclimation on the behavioural responses of the green crab (Carcinus maenas) from Newfoundland, Canada.

Effects of low temperature exposure and acclimation on the behavioural responses of the green crab (Carcinus maenas) from Newfoundland, Canada.

Corrigendum: Oyster grower perspectives on green crab (Carcinus maenas) interactions: using applied social science to inform research and engagement

Corrigendum: Oyster grower perspectives on green crab (Carcinus maenas) interactions: using applied social science to inform research and engagement

Wide Distribution but Low Differentiation: Genetic Diversity of Globose Shore Crab Cyclograpsus integer (Brachyura: Varunidae) along the Western Atlantic Ocean.

AbstractDecapod crustaceans with wide distributions have shown different patterns of population structure in certain species, which clarified processes related to population dynamics and intraspecific variation. The aim of the current study is to assess phylogeographic patterns of the intertidal crab Cyclograpsus integer H. Milne Edwards, 1837, as well as its wide distribution in the western Atlantic Ocean, from the US to Brazil. We hypothesize that the genetic structure of C. integer is influenced by the interaction of different geographic barriers. We analyzed partial sequences of the mitochondrial gene cytochrome c oxidase subunit I deriving from specimens collected along the western Atlantic distribution of C. integer. The phylogenetic reconstruction, haplotype networks, demographic history, divergence time, and discrete phylogeography of C. integer do not confirm our hypothesis. The wide distribution can be explained by the potential of C. integer larvae to disperse through northern Brazilian and Brazilian currents, which helps maintain gene flow across natural barriers. In addition, C. integer population size has increased in the Atlantic Ocean over the past 0.01-0.10 million years, with emphasis on two large separate groups and on the north-to-south spatiotemporal diffusion of its populations. While there is some evidence of genetic differentiation between the tropical northwestern Atlantic and the tropical/warm-temperate southwestern Atlantic regions, the overall genetic structure is low. The Amazon-Orinoco Plume appears to have limited influence as a barrier, further emphasizing the species' capacity for larval dispersal and genetic homogenization across its range. These findings highlight the importance of oceanographic features in shaping genetic patterns of widely distributed marine organisms and underscore the value of C. integer as a model for studying genetic connectivity in marine ecosystems.

The transition from resistance to acceptance: Managing a marine invasive species in a changing world

Abstract Marine invasive species can transform coastal ecosystems, yet mitigating their effects can be difficult, and even impractical. Often, marine invasive species are managed at poorly matched spatial scales, and at the same time, rates of spread and establishment are increasing under climate change and can outpace resources available for population suppression. These circumstances challenge traditional conservation goals of maintaining a historic environmental state, especially for a species like the European green crab (Carcinus maenas), a formidable invader with few examples of successful long‐term removal programs. A management paradigm where decision alternatives include resisting or accepting a new ecological trajectory may be needed. We apply mathematical concepts from decision theory to develop a quantitative framework for navigating management decisions in this new resist‐accept paradigm. We develop a model of European green crab growth, removal and colonization, and we find optimal levels of removal effort that minimize both ecological change and removal cost. We establish a benchmark of colonization pressure at which green crab density becomes decoupled from a decision maker's actions, such that population control can no longer shape the invasion trajectory. For informing the decision boundary between resistance and acceptance, our results highlight that a decision maker's understanding of how removal cost scales with removal effort is more important than understanding the density‐impact relationship. We show that assuming stationary system dynamics can result in sub‐optimal levels of species removal effort, highlighting the importance of developing anticipatory management strategies by accounting for non‐stationary dynamics. Policy implications. For marine invasive species that can disperse across long distances and recolonize rapidly after removal, the focus of conservation policy should shift away from understanding how to resist change to understanding when to stop resisting change. Navigating this decision problem involves trade‐offs among competing objectives, highlighting the need for structured approaches to elicit objective weights that reflect the values of the decision maker. For natural resource managers facing possible ecosystem transformation, this decision framework can enable proactive and strategic decisions made under uncertainty in a changing world.

Two cGMP-dependent protein kinases have opposing effects on molt-inhibiting hormone regulation of Y-organ ecdysteroidogenesis.

Decapod crustaceans regulate molting through steroid molting hormones, ecdysteroids, synthesized by the molting gland (Y-organ, YO). Molt-inhibiting hormone (MIH), a neuropeptide synthesized and secreted by the eyestalk ganglia, negatively regulates YO ecdysteroidogenesis. MIH signaling is mediated by cyclic nucleotide second messengers. cGMP-dependent protein kinase (PKG) is the presumed effector of MIH signaling by inhibiting mechanistic Target of Rapamycin Complex 1 (mTORC1)-dependent ecdysteroidogenesis. Phylogenetic analysis of PKG contiguous sequences in CrusTome as well as 35 additional species in NCBI RefSeq, identified 206 PKG1 sequences in 108 species and 59 PKG2 sequences in 53 species. These included four PKG1α splice variants in the N-terminal region that were unique to decapods, as well as PKG1β and PKG2 homologs. In vitro assays using YOs from the blackback land crab (Gecarcinus lateralis) and green shore crab (Carcinus maenas) determined the effects of MIH±PKG inhibitors on ecdysteroid secretion. A general PKG inhibitor, Rp-8-Br-PET-cGMPS, countered the effects of MIH, as ecdysteroid secretion increased in PKG-inhibited YOs compared to C. maenas YOs incubated with MIH alone. By contrast, a PKG2-specific inhibitor, AP-C5 (4-[4-(1H-Imidazol-1-yl)phenyl]-N-2-propyn-1-yl-2-pyrimidinamine), enhanced the effects of MIH, as ecdysteroid secretion decreased in G. lateralis and C. maenas YOs incubated with AP-C5 and MIH compared to YOs incubated with MIH alone. These data suggest that both PKG1 and PKG2 are activated by MIH, but have opposing effects on mTORC1-dependent ecdysteroidogenesis. A model is proposed in which the dominant role of PKG1 is countered by PKG2, resulting in low ecdysteroid production by the basal YO during intermolt.

The first record for the shore crab, Cyclograpsus aff. integer (Cyclograpsinae: Varunidae: Grapsoidea) from the Egyptian coasts of the Red Sea

The shore crab, Cyclograpsus aff. integer (Subfamily Cyclograpsinae, Family Varunidae: Superfamily Grapsoidea), is recorded for the first time from the Egyptian Red Sea coasts and from the entire Red Sea. This species is a small-sized crab, lives in burrows at the upper intertidal zone of the sandy-mud and sandy bottom mixed with small pebbles. The diagnostic characters with illustrations distinguished it from other closely allied species were given. All information on crab habitat, color, diagnostic and morphological characters of this species were given and discussed.

Insights into morphology of the 'columnar epithelium' within the female reproductive system of brachyuran crabs.

Insights into morphology of the 'columnar epithelium' within the female reproductive system of brachyuran crabs.

Experimental Infection of Enterocytozoon hepatopenaei (EHP) by Water and Sediment Transfer Between Pacific White Shrimp (Penaeus vannamei) and Green Mud Crab (Scylla paramamosain)

Experimental Infection of Enterocytozoon hepatopenaei (EHP) by Water and Sediment Transfer Between Pacific White Shrimp (Penaeus vannamei) and Green Mud Crab (Scylla paramamosain)