Carcinus Maenas Research Articles

The comparison of morphology and transcriptome in the inner membrane reveals the potential mechanism of the heritable carapace color of the Chinese mitten crab Eriocheir sinensis

Carapace color plays an important role in the communication, reproduction, and self-defense of crustaceans, which is also related to their economic value. Chinese mitten crab (Eriocheir sinensis) is an important aquaculture species in China, and there are different strains with heritable carapace colors, i.e. Green, White, and Red. However, there is a lack of research on the formation mechanism of carapace color of this species. This study was conducted to compare the histology and transcriptome in the inner membrane of three carapace color strains of E. sinensis. Histological comparisons revealed that the inner membrane of green and red carapace crabs contained more melanin, appearing in clusters, and had a higher presence of yellow or orange pigments. In contrast, the inner membrane of white carapace crabs had smaller and fewer melanin particles, as well as a lower presence of yellow or orange pigments. Observation under an electron microscope showed that the inner membrane of E. sinensis contained a large number of collagen fibers and various types of cells, including fibroblasts, melanocytes, and other tissue cells, which exhibited different levels of activity. Transcriptome analysis showed that the Green, Red, and White strains of E. sinensis had approximately 80.3 K, 81.6 K and 80.3 K expressed unigenes in their inner membranes, respectively. When comparing Green and Red crabs, there were 2, 850 upregulated genes and 2, 240 downregulated genes. In the comparison between Red and White crabs, there were 2, 853 upregulated genes and 2, 583 downregulated genes. Furthermore, there were 2, 336 upregulated genes and 2, 738 downregulated genes in the inner membranes between White and Green crabs. Among these genes, some members of the solute carriers family, which are involved in carotenoid transportation, showed differential expression among the three carapace color strains. Additionally, significant differences were observed in the expression of genes related to melanin synthesis, including wingless/integrate, tyrosinase, guanine nucleotide-binding protein inhibitory subunit, cell adhesion molecule, adenylyl cyclase, and creb-binding protein. there were no differences in the gene expression levels of the crustacyanin family. In conclusion, this study identified several candidate genes associated with carapace color in the inner membrane of E. sinensis, suggesting a close relationship between the heritable carapace colors and the transport of the carotenoids as well as the synthesis of melanin.

Local and regional geographic variation in inducible defenses.

Invasive predators can cause substantial evolutionary change in native prey populations. Although invasions by predators typically occur over large scales, their distributions are usually characterized by substantial spatiotemporal heterogeneity that can lead to patchiness in the response of native prey species. Our ability to understand how local variation shapes patterns of inducible defense expression has thus far been limited by insufficient replication of populations within regions. Here, we examined local and regional variation in the inducible defenses of 12 native marine snail (Littorina obtusata) populations within two geographic regions in the Gulf of Maine that are characterized by vastly different contact histories with the invasive predatory green crab (Carcinus maenas). When exposed in the field to waterborne risk cues from the green crab for 90 days, snails expressed plastic increases in shell thickness that reduced their vulnerability to this shell-crushing predator. Despite significant differences in contact history with this invasive predator, snail populations from both regions produced similar levels of shell thickness and shell thickness plasticity in response to risk cues. Such phenotypic similarity emerged even though there were substantial geographic differences in the shell thickness of juvenile snails at the beginning of the experiment, and we suggest that it may reflect the effects of warming ocean temperatures and countergradient variation. Consistent with plasticity theory, a trend in our results suggests that southern snail populations, which have a longer contact history with the green crab, paid less in the form of reduced tissue mass for thicker shells than northern populations.

Alteration of redox status and fatty acid profile in gills from the green crab (Carcinus aestuarii) following dimethoate exposure

Dimethoate is a broad-spectrum organophosphate insecticide and acaricide. Through various pathways, such as runoff and drift, dimethoate can reach marine environment, and easily impact common organisms in coastal areas, close to agriculture lands, namely crustaceans. The purpose of this study was to investigate the potential effects of dimethoate exposure (50, 100, and 200 μg/l), for 1 day, on a wide range of markers of oxidative stress and neurotransmission impairment, as well as fatty acids composition and histopathological aspect in the gills of the green crab Carcinus aestuarii. A significant increase in n-3 polyunsaturated fatty acids series, namely the eicosapentaenoic acid (C20: 5n3) and its precursor alpha-linolenic acid (C 18: 3n3) in dimethoate-treated crabs was recorded. Concerning n-6 polyunsaturated fatty acids, we noted a high reduction in arachidonic acid (C20:4n-6) levels. Dimethoate exposure increased the levels of hydrogen peroxide, malondialdehyde, lipid hydroperoxides, protein carbonyl, and caused the advanced oxidation of protein products along with enzymatic and non-enzymatic antioxidant-related markers. Acetylcholinesterase activity was highly inhibited following exposure to dimethoate in a concentration-dependent manner. Finally, deleterious histopathological changes with several abnormalities were noted in exposed animals confirming our biochemical findings. The present study offered unique insights to establish a relationship between redox status and alterations in fatty acid composition, allowing a better understanding of dimethoate-triggered toxicity.

Predation of the invasive green crab Carcinus maenas on the edible snail Buccinastrum deforme, targeted as the most important nearshore marine gastropod fishery from Patagonia, Argentina

Biological invasions constitute one of the main problems for the conservation of marine environments and are among the major causes of biodiversity reduction. The green crabs, Carcinus maenas was first reported on the Patagonian Argentinean coast in 2003 and has rapidly spread northwards along the coast. In 2018, many empty shells of the edible gastropod Buccinastrum deforme were observed at the shoreline, showing scars compatible with those caused by crab-crushing predations. This study aimed to evaluate the effect of C. maenas on the edible gastropod B. deforme, a species of great fishing importance in Patagonia, Argentina. In order to characterize the green crab’s predatory marking patterns observed on the shell of B. deforme, aquarium experiments were conducted. At the same time, field sampling census of shells stranded in the intertidal zone were carried out in three different sites where high densities of B. deforme were previously recorded. Empty shells showing the characterized marking patterns were used as an indicator of predation and were randomly collected from the intertidal to quantify the frequency of each type of predatory mark. Additionally, the abundance of snails and crabs was estimated using baited traps in ten sampling sites. Our results are consistent with the fact that the non-native green crab C. maenas presents a highly aggressive behavior that affects native species' abundances once established in a new environment. The most frequent pattern of predation marks was the combined crush of the apex and lip, occurring simultaneously in the same individual. A decrease in B. deforme presence was inversely proportional to the increase in C. maenas populations. This is the first work that records the impact of predation of the invasive species C. maenas on Atlantic Patagonia's sandy bottoms, which negatively affects a fragile species such as the edible snail B. deforme. The dispersal capacity of the green crab, in addition to its predatory strength and voracity, could endanger the artisanal fishery of B. deforme and induce irreversible changes in the coastal ecosystems of Atlantic Patagonia.

Artificial light at night alters predation on colour-polymorphic camouflaged prey

Artificial light at night (ALAN) disrupts biological processes across taxa and at all levels of organisation. Despite growing interest in this globally pervasive sensory pollutant, its impact on colour-guided processes remains largely unexplored. This is especially concerning given the rapid transition in recent years away from narrow-spectrum lighting and towards broad-spectrum options such as white LEDs, which are rich in the short wavelengths of light to which many taxa are particularly sensitive. Camouflage is particularly likely to be disrupted by broader spectra of ALAN due to changes in conspicuousness in background matching prey, which may alter prey recognition in visually guided predators. We simulated natural intensities of moonlight with and without ALAN, using both broad-spectrum (‘white’) ALAN and ALAN filtered to remove the characteristic short (blue) wavelength peak of broad-spectrum LEDs to test whether filtering might mitigate their effects. We tested how exposure to these light treatments impacted predator-prey interactions, using the intertidal crab Carcinus maenas and contrasting colour morphs of the colour-polymorphic snail Littorina obtusata as a model system. Exposure to broad-spectrum ALAN reduced overall predation and reversed the pattern of colour-based prey selection observed under control conditions. Snails were 55 % less likely to be attacked under broad-spectrum ALAN than in control conditions, with likelihood decreasing over 70 % for yellow snails. Yellow snails were over 26 % more likely to be attacked than brown ones under control conditions, but brown snails were over 40 % more likely to be attacked than yellow ones under broad-spectrum ALAN. Exposure to filtered ALAN removed any significant colour-based difference in prey recognition. Our results demonstrate that spectral composition is a crucial aspect of ALAN as a sensory pollutant, capable of instigating profound changes in predator-prey interactions that could drive changes in population demography and increase morphological homogeneity in species that depend on colour polymorphism for camouflage.

Horizon scanning for potentially invasive non-native marine species to inform trans-boundary conservation management – Example of the northern Gulf of Mexico

Prevention of non-native species introductions and establishment is essential to avoid adverse impacts of invasive species in marine environments. To identify potential new invasive species and inform non-native species management options for the northern Gulf of Mexico (Alabama, Mississippi, Louisiana, Texas), 138 marine species were risk screened for current and future climate conditions using the Aquatic Species Invasiveness Screening Kit. Species were risk-ranked as low, medium, high, and very high risk based on separate (calibrated) thresholds for fishes, tunicates, and invertebrates. In the basic screening, 15 fishes, two tunicates, and 26 invertebrates were classified as high or very high risk under current climate conditions. Whereas, under future climate conditions, 16 fishes, three tunicates, and 33 invertebrates were classified as high or very high risk. Very high risk species included: California scorpionfish Scorpaena guttata, red scorpionfish Scorpaena scrofa, purple whelk Rapana venosa, and Santo Domingo false mussel Mytilopsis sallei under both current and future climates, with weedy scorpionfish Rhinopias frondosa, Papuan scorpionfish Scorpaenopsis papuensis, daggertooth pike conger Muraenesox cinereus, yellowfin scorpionfish Scorpaenopsis neglecta, tassled scorpionfish Scorpaenopsis oxycephalus, brush-clawed shore crab Hemigrapsus takanoi, honeycomb oyster Hyotissa hyotis, carinate rock shell Indothais lacera, and Asian green mussel Perna viridis under climate change conditions only. This study provides evidence to inform trans-boundary management plans across the five Gulf of Mexico states to prevent, detect, and respond rapidly to new species arrivals.

Trophic ecophysiology of the native green shore crab, Carcinus maenas, and the invasive Asian shore crab, Hemigrapsus sanguineus, in the rocky intertidal of Helgoland (North Sea)

The brachyuran crabs Carcinus maenas and Hemigrapsus sanguineus belong to the most ´successful´ invaders along the oceans coasts. In 2009, H. sanguineus appeared at the rocky intertidal of the island of Helgoland in the North Sea, where it encounters the native Green shore crab, C. maenas. H. sanguineus established a self-sustaining population, approaching in numbers and biomass that of C. maenas. Both species are considered to be opportunistic omnivores with variable food preferences and, thus, are potential competitors for food. To evaluate the intrinsic properties of either species to utilize food, we analyzed their stomach content, the morphology of the gastric mills, which shred the ingested food, the activities of digestive enzymes during a seasonal cycle, and the stable isotope ratios. A huge share of the stomach contents was macerated and, thus, could not be identified. The shares of animal food and algae food were almost equal in C. maenas but algae food dominated over animal food in H. sanguineus. The gastric mill of C. maenas shows blunt medial tooth and rounded lateral teeth, which indicates efficient grinding of a carnivorous diet. In contrast, the gastric mill of H. sanguineus shows sharp ridges, which facilitate cutting of algal food. The activities of the proteolytic enzymes trypsin and leucine-aminopeptidase were almost equal in both species with slightly higher activities in C. maenas in summer. The activities of the carbohydrases laminarinase and amylase dominated in H. sanguineus during all seasons. Stable isotope ratios indicate a higher degree of carnivory in C. maenas. The morphological and biochemical features indicate that C. maenas is better suited to utilize animal food and H. sanguineus algal food. Upon scarcity of animal food or severe competition with C. maenas, H. sanguineus may be able to increase the amount of algal food and to utilize it efficiently.

On the rebound: removal programs yield local-scale benefits but do not sustainably suppress populations of invasive European green crabs (Carcinus maenas)

On the rebound: removal programs yield local-scale benefits but do not sustainably suppress populations of invasive European green crabs (Carcinus maenas)

Thermal acclimation and habitat-dependent differences in temperature robustness of a crustacean motor circuit.

At the cellular level, acute temperature changes alter ionic conductances, ion channel kinetics, and the activity of entire neuronal circuits. This can result in severe consequences for neural function, animal behavior and survival. In poikilothermic animals, and particularly in aquatic species whose core temperature equals the surrounding water temperature, neurons experience rather rapid and wide-ranging temperature fluctuations. Recent work on pattern generating neural circuits in the crustacean stomatogastric nervous system have demonstrated that neuronal circuits can exhibit an intrinsic robustness to temperature fluctuations. However, considering the increased warming of the oceans and recurring heatwaves due to climate change, the question arises whether this intrinsic robustness can acclimate to changing environmental conditions, and whether it differs between species and ocean habitats. We address these questions using the pyloric pattern generating circuits in the stomatogastric nervous system of two crab species, Hemigrapsus sanguineus and Carcinus maenas that have seen a worldwide expansion in recent decades. Consistent with their history as invasive species, we find that pyloric activity showed a broad temperature robustness (>30°C). Moreover, the temperature-robust range was dependent on habitat temperature in both species. Warm-acclimating animals shifted the critical temperature at which circuit activity breaks down to higher temperatures. This came at the cost of robustness against cold stimuli in H. sanguineus, but not in C. maenas. Comparing the temperature responses of C. maenas from a cold latitude (the North Sea) to those from a warm latitude (Spain) demonstrated that similar shifts in robustness occurred in natural environments. Our results thus demonstrate that neuronal temperature robustness correlates with, and responds to, environmental temperature conditions, potentially preparing animals for changing ecological conditions and shifting habitats.

Investigating the impact of introduced crabs on the distribution and morphology of littorinid snails: Implications for the survival of the snail Littorina saxatilis

Introduced species can have profound impacts on communities by displacing and consuming native organisms. The intertidal communities in the Gulf of Maine have been radically altered through a suite of invasions in the early 1800s, including the herbivorous snail Littorina littorea and the omnivorous European green crab Carcinus maenas leading to morphological and distributional changes in two native gastropod grazers (Littorina saxatilis and Littorina obtusata). Green crabs and native cancrid crabs occupy the mid to low intertidal zones, leaving the high intertidal zones relatively free from crab predation pressure. However, a more recent invasion in the 1980s by the intertidal omnivorous Asian shore crab Hemigrapsus sanguineus, has eliminated this predator-free zone in the high intertidal. This invasion is of particular concern to populations of L. saxatilis, which were relegated to the high intertidal through combined competition and predation pressure by L. littorea and C. maenas. In order to quantify the potential impact of H. sanguineus on native snails, we conducted both field and lab experiments, testing the susceptibility of different sized snails to predation by introduced crabs. Additionally, we measured the distribution, abundance, and morphology of intertidal snails and crabs. Smaller snails of all species were the most susceptible to predation, although susceptibility differed among snail species and predation capabilities differed among crab species. L. saxatilis was the most vulnerable snail species to predation, with 73 and 64% of the population susceptible to large H. sanguineus and small C. maenas, respectively, while >96% of the L. littorea population was resistant to predation. L. saxatilis has been relegated to the high intertidal where there is high abiotic stress and poor-quality food, but until the invasion of H. sanguineus, there was little predation risk. This added predation pressure may further threaten populations of L. saxatilis, especially as the upper intertidal becomes more hostile with increasing temperatures and possible species introductions.

Implications of Warming on the Morphometric and Reproductive Traits of the Green Crab, Carcinus maenas

Understanding the relationship between environmental temperature and the biological traits of organisms is fundamental to inferring the potential impacts of climate change. In the case of marine poikilotherm species, seawater temperature is one of the main driving forces of biological processes, with consequences at higher levels of organization such as population and ecosystem. In this study, we analysed differences in maximum carapace width (CWmax), size at maturation, relative size at maturation, and duration of the reproductive season for the green crab (Carcinus maenas) along a temperature gradient. An extensive review of bibliographic data was performed on studies published between 1962 and 2020, gathering C. maenas data from 55 different populations, spread over 20 degrees of latitude and 14.2 °C of sea surface temperature (SST). In addition, green crab data were collected at five different lagoons and estuaries along the continental Portuguese coast. The relationship between average SST and CWmax, age of maturation, reduction of size at maturation, and duration of egg bearing was analysed to understand the role of SST in driving variation in these C. maenas characteristics across a latitudinal gradient. There was a significant relationship between SST and CWmax for males and SST and CW of females at maturation, respectively. The results extrapolate for each local projected temperature increase caused by climate change and suggest an effect on the morphometric and reproductive traits of C. maenas across regions. These changes comprise an overall reduction in C. maenas body size, an enlargement of the reproductive season, a shortening in the duration of larval developmental time, and a decrease in the relative size of crabs at maturation. Secondary consequences on the fecundity and connectivity of populations are discussed.

The impact of food availability on risk-induced trait responses in prey

Abstract Prey respond to predation risk by altering their morphology, physiology, and behavior, responses that may come at a cost to prey foraging and growth. However, their perception of risk may depend upon the environmental context in which the interaction occurs. Here, we examined how food availability influenced prey’s responses to a nonlethal but free-ranging predator. We used an experimental mesocosm set-up of an intertidal system of green crab (Carcinus maenas) predators and dogwhelk snail (Nucella lapillus) prey, with blue mussels as the basal resource. We measured individual Nucella risk-aversion behavior (summed value of their habitat use) and their growth throughout the 28-day experiment. We found that when Nucella were exposed to predation risk, they had greater risk-aversion behavior when food was available as compared to when food was not. We also found that risk-aversion behavior increased over time in all treatments but that individuals exposed to predation risk with food always had greater risk-aversion behavior. Nucella had significantly more growth when provided with food as compared to without. In treatments with food, snails exposed to predation risk had significantly reduced growth compared to those not exposed to risk. In treatments without food, predation risk had no effect on growth. Our results support the hypothesis that greater resource availability significantly increases individual risk responses and the costs of risk avoidance, thus food magnifies risk-induced non-consumptive effects. They provide insights into context-based predation risk effects and how individuals may prioritize safety versus foraging depending upon perceived risk, food availability, and the costs of responding.

Differential analysis of the haemolymph proteome of Carcinus maenas parasitized by Sacculina carcini (Cirripeda, Rhizocephala) reveals potential mechanisms of parasite control

Sacculina carcini is an endoparasite of the green crab, Carcinus maenas. This parasite induces behavioural changes in its host and affects its metabolism by inhibiting moulting and reproduction. Using a proteomic approach in mass spectrometry, we studied the haemolymph proteomes of healthy and parasitized wild green crabs from Brittany, France to identify proteins that are differentially expressed as a consequence of parasitization. We also investigated specific proteins involved in reproduction, moulting, and immunity. We detected 77 proteins for females and 53 proteins for males that were differentially present between the healthy and parasitized crabs, some of which were sex-specific. Detection of these differentially expressed proteins suggests that the parasite can inhibit and promote different aspects of the immune response of the host. Sacculina appears to inhibit host melanisation for self-protection, while promoting the presence of immune factors, such as antimicrobial peptides to cope with possible bacterial superinfections. Moreover, one protein, juvenile hormone esterase-like carboxylesterase, was 17-times more abundant in parasitized crabs than in healthy crabs and may be responsible for inhibiting moulting and reproduction in parasitized crabs, thus ensuring the success of Sacculina reproduction.

Macro and microscopic maturation stage key of green crab (Carcinus maenas, Linnaeus 1758): Reproductive cycle and differences among estuarine systems

Gonadal histology is a helpful tool to validate species' macroscopic maturity stages in fisheries biology. Regardless of the many studies on Carcinus maenas, there are still few concerning gonads tissue histology and description of maturity stages. In Portugal, information regarding this species' biology to help support the regulation of crab fisheries, including the minimum landing size, has not yet been defined. In this work, the macro and microscopic characteristics of the reproductive cycle of C. maenas, oogenesis, and spermatogenesis development stages along the Portuguese coast are described, and a new macroscopic scale based on the histological analyses is suggested. During 2019 and 2020, adult C. maenas (both males and females) were collected from the Ria de Aveiro estuary, Rio Sado estuary, and Ria Formosa lagoon, respectively, North, Center, and South Portugal. No-significant differences (P > 0.05) were observed in carapace width and individual weight between all systems. Significant differences (P < 0.05) were observed in gonad weight, gonadosomatic index, and Fulton's condition index between the Rio Sado estuary and Ria Formosa lagoon. Furthermore, significant differences (P < 0.05) in the oocyte diameter between the northern and southernmost locations suggest a geographic variation related to the local environmental conditions of each system. Principal component analysis (PCA) revealed maturity stage and carapace width an association, and a similar morphometry between Ria de Aveiro and Ria Formosa. Temperature was correlated to both maturity stage and carapace width in Ria de Aveiro and Ria Formosa. From the histological analysis and based on microscopic criteria, it was observed that females previously classified within the late macroscopic development stage 2 should be considered mature, so a classification change in the current ovary's developmental stage is proposed. These findings can allow fisheries researchers to reclassify the estimations of maturity ogives and help support the regulation of this species' fishery. The proposed macroscopic scale was validated by histological analyses and can be used elsewhere.

Identification and functional analysis of endoplasmic reticulum oxidoreductase 1 (ERO1) from the green mud crab Scylla paramamosain: The first evidence of ERO1 involved in invertebrate immune response.

Endoplasmic reticulum oxidoreductase 1 (ERO1) is an important mediator in regulating disulfide bond formation and maintaining endoplasmic reticulum homeostasis. Its activity is transcriptionally regulated by the unfolded protein response (UPR) in the endoplasmic reticulum, which is known to be essential in immunity. However, whether ERO1 is involved in innate immunity in invertebrates remains unclear. In the present study, two subtypes of ERO1 from Scylla paramamosain were first identified and characterized. Sequence analysis revealed the conserved ERO1 domain and the oxidative capacity assay verified the oxidative capacity of SpERO1 recombinant protein. Moreover, SpERO1s were found to be ubiquitously expressed in all the tested tissues, with the highest expression observed in hemocytes. Two SpERO1s exhibited distinct expression patterns in response to Vibrio alginolyticus and White Spot Syndrome Virus (WSSV). Importantly, the downregulation of the expression of immune factors upon bacterial challenge in SpERO1-silenced crabs was observed. These results provided an initial foundation for further investigations into the role of ERO1 in the innate immunity of invertebrates.

The role of octopamine and crustacean hyperglycemic hormone (CHH) in branchial acid-base regulation in the European green crab, Carcinus maenas.

Crustaceans' endocrinology is a vastly understudied area of research. The major focus of the studies on this topic to date has been on the molting cycle (and in particular, the role of crustacean hyperglycemic hormone (CHH)), as well as the role of other hormones in facilitating physiological phenotypic adjustments to salinity changes. Additionally, while many recent studies have been conducted on the acclimation and adaptation capacity of crustaceans to a changing environment, only few have investigated internal hormonal balance especially with respect to an endocrine response to environmental challenges. Consequently, our study aimed to identify and characterize endocrine components of acid-base regulation in the European green crab, Carcinus maenas. We show that both the biogenic amine octopamine (OCT) and the CHH are regulatory components of branchial acid-base regulation. While OCT suppressed branchial proton excretion, CHH seemed to promote it. Both hormones were also capable of enhancing branchial ammonia excretion. Furthermore, mRNA abundance for branchial receptors (OCT-R), or G-protein receptor activated soluble guanylate cyclase (sGC1b), are affected by environmental change such as elevated pCO2 (hypercapnia) and high environmental ammonia (HEA). Our findings support a role for both OCT and CHH in the general maintenance of steady-state acid-base maintenance in the gill, as well as regulating the acid-base response to environmental challenges that C. maenas encounters on a regular basis in the habitats it dwells in and more so in the future ocean.

A novel method for quantifying the attractiveness of lobster trap baits

We developed a new method for quantifying the attractiveness of bait in traps used for crustacean fisheries by using accelerometers in bait containers to assess the amount of time animals spend interacting with the baits. We validated our approach in the laboratory by using time-lapse video recordings to verify that the accelerometry data accurately reflected when, and how much, American lobsters (Homarus americanus) interacted with bait. We then conducted a field experiment comparing traps baited with traditional herring, crushed green crabs (Carcinus maenas), or an inert control. We found that during 48-h trap sets, the number of minutes in which the accelerometers recorded movements of the bait bags was correlated with lobster catch. Although the traps baited with herring did not catch significantly more lobsters than traps baited with crushed green crabs, the accelerometer data revealed differences in bait attractiveness over time. Lobsters interacted less with the green crab bait on the second day of the set, while no such decline was observed with the herring bait. This technique is inexpensive, easy to use, and the data obtained can be more rapidly analyzed than the video data traditionally used for these types of studies, making it well suited for future work on bait choice and attractiveness.

Past energy allocation overwhelms current energy stresses in determining energy allocation trade-offs.

Regeneration of lost appendages is a gradual process in many species, spreading energetic costs of regeneration through time. Energy allocated to the regeneration of lost appendages cannot be used for other purposes and, therefore, commonly elicits energetic trade-offs in biological processes. We used limb loss in the Asian shore crab Hemigrapsus sanguineus to compare the strength of energetic trade-offs resulting from historic limb losses that have been partially regenerated versus current injuries that have not yet been repaired. Consistent with previous studies, we show that limb loss and regeneration results in trade-offs that reduce reproduction, energy storage, and growth. As may be expected, we show that trade-offs in these metrics from historic limb losses far outweigh trade-offs from current limb losses, and correlate directly with the degree of historic limb loss that has been regenerated. As regenerating limbs get closer to their normal size, these historical injuries get harder to detect, despite the continued allocation of additional resources to limb development. Our results demonstrate the importance of and a method for identifying historic appendage losses and of quantifying the amount of regeneration that has already occurred, as opposed to assessing only current injury, to accurately assess the strength of energetic trade-offs in animals recovering from nonlethal injury.

New records of rarely reported species in the Mediterranean Sea (July 2023)

This Collective Article presents new information about the occurrence of 23 marine taxa that belong to five Phyla: two Chlorophyta, one Annelida, six Mollusca, three Arthropoda, eleven Chordata (one Ascidiacea, one Elasmobranchii and nine Teleostei) and extending from the Western Mediterranean to the Levantine Sea. All these records were reported from nine countries from the western to the eastern Mediterranean Sea, with a broad biogeographical coverage as follows: Spain: first records of the sacoglossans Cyerce graeca and Placida tardyi for the Alboran Sea and first records of the nudibranch Marionia gemmii for the Mediterranean waters of Spain; first records of nudibranch Algarvia alba in the Mediterranean Sea. Italy: First report of the long-legged crab Paragalene longicrura, a further new Mediterranean record of the rare offshore rockfish Pontinus kuhlii, first documented record of the spiny butterfly ray Gymnura altavela in Sardinia (Tyrrhenian Sea), new record of the red‐spotted wrasse Lappanella fasciata from the Messina Strait, first documented record of the rarely observed brown moray Gymnothorax unicolor in the Ionian coast, first record of the colonial ascidian Botrylloides israeliensis, first record of the Morocco dentex Dentex maroccanus, first record of mottled shore crab Pachygrapsus maurus and of an adult specimen of barracudina Lestidiops sphyrenoides in the Adriatic Sea, and further new Mediterranean records of Ross worm Sabellaria spinulosa along the same coast. Tunisia: second record of smalleye squaretail Tetragonurus cuvieri from the African Mediterranean coast. Slovenia: first records of the sea slug Trapania graeffei and Melanochlamys wildpretii, with the last one also representing the northernmost finding of this species. Croatia: northernmost record of the endangered twaite shad Alosa fallax in the Adriatic coast. Albania: first records of the Mediterranean spearfish Tetrapturus belone. Türkiye: first record from the Aegean coasts for Türkiye of the green macroalgae Cladophora battersii and Valonia aegagropila. Israel: first record of the skeleton shrimp Caprella acanthifera in the Southeastern Mediterranean Sea. Syria: first record of the Smooth grenadier Nezumia aequalis from Syrian marine waters.

Interspecies and spatial differences in the shell microbiome of Atlantic rock crab Cancer irrotatus and European green crab Carcinus maenas from Atlantic Canada

IntroductionThe native Atlantic rock crab (Cancer irrotatus) and the invasive European green crab (Carcinus maenas) are commercially and ecologically important crustacean species in Atlantic Canada. The importance of microbiomes for host health and ecology has been recognized in many species, although very few studies have focused on crustaceans or their external shell microbiome. This is the first-ever study to characterize and analyze the microbial communities associated with the external carapace of C. irrotatus and C. maenas.MethodsMicrobiome samples were collected from three locations in Atlantic Canada, processed using standard 16S Illumina MiSeq PE250 sequencing and analyzed with the open-access QIIME2 software.ResultsTaxonomic classification of the microbial compositions, as well as alpha- and beta diversities, reveal that the shell microbiome differs by host species between C. irrotatus and C. maenas sampled from the same location and between C. irrotatus sampled from different locations. Interestingly, the differences are greater between species at the same location than between locations for the same species.DiscussionThese are the first-ever results showing that the crustacean shell microbiome not only depends on geographical factors but also on intrinsic factors specific to the host species. This implies that crustaceans exert some impact on their shell microbiome, potentially selecting beneficial taxa. These are important findings that could elucidate contributing factors of crustacean shell diseases that are still poorly understood.