Crab Larvae Research Articles

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.

Larval development of the blue crab Callinectes sapidus: effect of enriched rotifers as live food

Understanding nutrition and its effect on growth is essential for developing diets in commercially important species. This study aimed to evaluate the larval development of Callinectes sapidus fed with rotifers (Brachionus plicatilis) enriched with Chlorella pyrenoidosa (Ch) as a main protein source and a lipid emulsion (Spr) rich in highly unsaturated fatty acids. The enriched compositions had seven ratios Ch/Spr (w/w): 100/0, 90/10, 80/20, 70/30, 60/40, 50/50, and 40/60. The enriched rotifers with each ratio were called diets. Lipids increased progressively between 100/0 and 40/60 (7.48 to 11.30 g 100 g-1), as well as energy (21.88 to 23.16 kJ g-1), but the protein level did not show a clear trend (63.93 and 67.50 g 100 g-1). The production response of blue crab larvae showed significant differences within diets (P < 0.05). The highest survival (29 to 34%) was obtained in the 50/50 and 40/60 treatments. In the 40/60, 50/50, and 60/40 diets, the larval cycle was shorter (P < 0.05), and the megalopa stage was reached between 49 and 52 days of culture. Metamorphosis to megalopa occurred between the fifth and eighth molts; its corresponding weight varied from 0.72 to 1.33 mg, the length varied from 2,632 to 2,926 µm, and Le Cren´s condition factor varied from 0.83 to 1.16. The most important factor in the production response was the diet lipid content, which was significantly correlated with the survival, weight, length, and condition factor of C. sapidus larvae. Findings of the present study can be applied in future efforts towards mass culture of blue crab larvae in the Caribbean and can also potentially be used to study other crustacean species with similar characteristics.

Modelled dispersal of snow crab (Chionoecetes opilio) larvae and potential settlement areas in the western Barents Sea

Abstract Since the mid-1990s, a snow crab (Chionoecetes opilio) population has established in the eastern Barents Sea. Spawning females and newly hatched larvae are now also found in the central Barents Sea, warranting speculations on a further westward colonization by pelagic larvae. Here, we model the potential for larval dispersal and settlement into uncolonized areas in the western Barents Sea. We used a biophysical model of ocean currents and hydrography, coupled with a Lagrangian dispersal algorithm and larval survival functions as response to temperature. The model predicts limited dispersal from the central Barents Sea to western areas, primarily due to a mismatch between prevailing temperature regimes and temperature tolerances for the different larval stages. In addition, there was limited westward transport of water masses with temperatures that would allow completion of the pelagic larval development. We speculate that for larvae to successfully supply benthic recruits to the remaining uncolonized areas in the western Barents Sea, adult crabs would first need to establish new spawning aggregations, for example along the western slopes of the Barents Sea shelf. Immediate implications are limited potential for expanding the fishery to the western areas of the Barents Sea.

Effect of Diet on Growth Performance of First Crab Stage Callinectes sapidus Rathbun, 1896 (Brachyura: Portunidae): A Comparison of Three Different Regimens

This study aimed to supply three foods to the crab Callinectes sapidus in its juvenile stage and compare their effects on its growth. For that, crab larvae were cultured from oviparous adult female crabs. The larvae (z1-z8) were fed with rotifers, previously cultured with microalgae and megalopae (Meg.) with live Artemia salina larvae, obtained from fresh cysts until they reached juvenile development (c1, first crab). Then, 270 animals (c1) were analyzed in three groups of 90, with different diets: shrimp (Penaeus vannamei; Group 1), squid (Mastigoteuthis flammea; Group 2), and tilapia fish (Oreochromis niloticus; Group 3). After 90 days of feeding regimens, the sizes of juvenile crabs were measured by microscopy, and the following relationship was found (p < 0.001): Group 1 (20.8 ± 0.7) > Group 2 (14.5 ± 0.9) > Group 3 (10.4 ± 0.6). The nutritional factor played an essential role in this size differentiation. This intelligent and differentiated feeding strategy showed us that shrimp could be an essential source for the growth of crabs in the juvenile stage. This new approach to safe and efficient roost feeding can classify crabs by size for further hormonal, molting, and reproductive studies.

Predators Induce Phenotypic Plasticity in Echinoderms across Life History Stages.

AbstractMarine invertebrates with biphasic life cycles feature life history transitions that coincide with habitat changes from benthic adults to planktonic embryos and larvae, then a return to the benthos as a juvenile at metamorphosis. The metamorphic transition exposes animals to a new suite of benthic predators, and high mortality often occurs in the hours and days following settlement. Juvenile invertebrates may produce phenotypically plastic morphological defenses when predator cues are detected. However, time lags inherent to phenotypic plasticity may delay the production of defenses until after the period of highest vulnerability. It should, therefore, be beneficial for planktonic larvae approaching settlement to detect waterborne cues from benthic predators and produce juvenile phenotypes appropriate for postmetamorphic survival. Echinoderms are useful models for testing transhabitat and trans-life history stage phenotypic plasticity because many species have larvae that construct their juvenile phenotype while still in the water column. In this study, we tested whether planktonic echinoderm larvae exposed to cues from benthic predators modified their juvenile phenotypes at settlement. Green urchin (Strongylocentrotus droebachiensis) and Pacific sand dollar (Dendraster excentricus) larvae were exposed to predatory green crab (Carcinus maenus) or red rock crab (Cancer productus) cues, respectively, from their early-stage juvenile rudiment formation through settlement. Green urchin larvae exposed to predator cues settled with significantly more juvenile spines compared to unexposed controls. Sand dollars exhibited earlier settlement, larger disk area, fewer spines, and shorter spines when exposed to benthic predator cues. Sand dollar larvae were also exposed to cues from planktonic crab larvae and in response settled sooner and larger, with even fewer and shorter spines than those exposed to benthic predator cues. These results suggest that echinoderm larvae alter their juvenile phenotype in response to predator cues, but the response varies between species, and responses to planktonic threats may be prioritized over benthic ones.

Comparative transcriptome, digital gene expression and proteome profiling analyses provide insights into the brachyurization from the megalopa to the first juvenile in Eriocheir sinensis

Eriocheir sinensis larva normally experiences 11 stages. The reduced abdomen folded beneath the thorax is the most prominent characteristic of morphological alteration from megalopa to juvenile crab. Up to date, the molecular mechanisms of brachyurization remain a mystery. Here, transcriptome library, digital gene expression (DGE) libraries and proteome libraries at two developmental stages [the megalopa stage of E. sinensis (stage M) and the first stage of juvenile crab (stage J1)] of the Chinese mitten crab larva were constructed for RNA sequencing and iTRAQ approaches followed by bioinformatics analysis, respectively. In total, 1106 genes and 871 proteins were differentially expressed between the stage M and stage J1. Moreover, several important pathways were identified, including biosynthesis of secondary metabolites, metabolic pathways, focal adhesion, and some disease pathways. Besides, muscle contraction, oxidative phosphorylation, calcium signaling, PI3K-Akt, DNA replication pathway, and integrin signaling pathway also had important functions in brachyurization process. Furthermore, the components, actin, actin-related protein, collagens, filamin-A/B, laminin, integrins, paxillin, and fibronectin had up-regulated expression levels in M stage compared to J1 stage.

Distribution and General Biological Features of Snow Crab (&lt;i&gt;Chionoecetes opilio&lt;/i&gt;) in the Chukchi and East Siberian Seas

Hydrobiological surveys (plankton and benthos, including snow crab) were carried out in the summer of 2003–2020 in the south-western region of the Chukchi Sea. At the west, east, and north edges of C. opilio distribution area in the Chukchi Sea the amounts of the crabs were 5–10 times lower due to the limit of species’ tolerance to hydrological factors and inappropriate trophic base – low mass of zoobenthos. Some gatherings of snow crab C. opilio in northern regions of the Chukchi and the East-Siberian Seas can be considered as dependent, which depends on income from southern regions of the Chukchi Sea. The southern regions of the Chukchi Sea are some kinds of the nursery for development and growth of snow crab larvae and youth until 1–2 years age, from where they migrate into northern deeper regions of the Chukchi Sea, and then more fare into north-eastern region of the East-Siberian Sea.

FINDING OF THE MUD CRAB &lt;i&gt;DYSPANOPEUS SAYI &lt;/i&gt;(S. I. SMITH, 1869) (BRACHYURA: XANTHOIDEA: PANOPEIDAE) IN THE SEA OF AZOV

The mud crab Dyspanopeus sayi (S.I.Smith, 1869) was recorded in the waters of the European part of Russia in the coastal zone of the Kazantip Peninsula (Shelkovitsa bay) on the northern coast of the Kerch Peninsula and near the Arshintsevskaya Spit (Kerch) in August 2022 for the first time. The species natural geographic range is located along the entire Atlantic coast of North America and the invasion range includes the coastal waters of the Atlantic coast of Europe, the northern part of the Mediterranean Sea and the western part of the Black Sea. Discovered in the Black Sea off the coast of Romania in 2009, D. sayi has significantly expanded its distribution area in the Azov-Black Sea basin for the past 10 years. The most likely spread of this species by anthropogenic means as a result of intake, transportation and discharge of ballast water by marine transport vehicles, but the option of colonization from existing areas of settlement by transfer of crab larvae with marine currents cannot be excluded. The presence of females with eggs and different-sized crab specimens may indicate the presence of already established populations of mud crab D. sayi in the coastal areas of the Sea of Azov. D. sayi is an active invasive species inhabiting transitional waters between continental water bodies and the sea. Therefore, it is important to monitor the distribution of this crab in order to predict consequences for local species and ecosystems.

Food Composition and Feeding Intensity of Channa Striata from Selected Stations of River Krishna, Andhra Pradesh

Aim of the current piece of work was to study the food composition and feeding intensity of Channa striata from Krishna river from June, 2019 to July 2020. The gut contents were analysed from the three stations to undertaken the food composition of the fish. The major components of food items in the gut of fish was: fishes and their larvae, crustaceans, insect larvae, annelids with semi digested material and unidentified items. Fishes are identified as of teleost, particularly carps and cat fish larvae but most of the fishes leftovers could not be recognized since they are found in advanced phases of digestion with only scales &amp; skeleton remains. Gastropods are identified as polycheate larvae, and Crustaceans are prawn and crab larvae. The percentage occurrence of fishes and their larvae in gut contents and also feeding intensity were indicated that C. striata preferential food was fishes followed by crustaceans.

EFFECT OF ROTIFER DENSITY ON SURVIVAL AND DEVELOPMENT OF MUD CRAB SCYLLA SERRATA (FORSKÅL) LARVAE

An experiment of mud crab, Scylla serrata with single factor design was set up at the Marine and Aquaculture Research Unit of James Cook University, Queensland, Australia for 26 days in order to improve the hatchery technique, i.e development and survival of larvae using different rotifer densities. The mud crab larvae were reared at 0, 5, 10, 20, 40, and 60 ml-1 rotifer densities. Survival and development increased with the increase of rotifer density. At higher rotifer density situation, the highest 35-40% survival of Z-I stage was achieved at 40-60 ml l-1. Higher density beyond 40 ml l-1 resulted in higher mortality which needs further investigation. Moreover, rotifer was found as suitable diet for Z-I and Z-II larvae. From Z-III onwards, rotifers were found not suitable for the larval survival and development of mud crab larvae.

Deterioration of Coastal Ecosystem: A Case Study of the Banana Bay Ecological Reserve in Taiwan

Due to the increasing pressure on the environment from human activities, there is a growing need to understand the relationship between species and the environment. Therefore, this study constructs life cycle and niche from a geographic perspective, aiming to explain how existing spatial configurations affect the deterioration of coastal ecosystems. This research mainly adopts the method of literature analysis and field investigation, and then carries out four steps of reading, sorting, integration and analysis. In this study, the road kill data and living environment data of land crabs were integrated, and two results were obtained on the relationship between spatial conflict areas and land crab populations. The first is that the life cycle of land crabs is disturbed by TPH 26, thus confirming the spatial conflict hypothesis; the peak period of traffic flow at TPH 26 overlapped with the peak period of land crab larvae release, indicating that the spatial configuration of the reserve is not only a spatial conflict, but also a spatial-temporal conflict. Second, the land crab is an important indicator of coastal forests, and its niche also reflects geographic diversity, especially in features such as topographic structure, geological stability, and environmental humidity.

Enhancement of protein, lipid and fatty acids in copepod, Oithona rigida for the improvement of growth, development and survival of early‐stage mud crab larvae ( Scylla olivacea )

Enhancement of protein, lipid and fatty acids in copepod, <i>Oithona rigida</i> for the improvement of growth, development and survival of early‐stage mud crab larvae ( <i>Scylla olivacea</i> )

Ecology and Distribution of Red King Crab Larvae in the Barents Sea: A Review

The red king crab (RKC) is a large invasive species inhabiting bottom communities in the Barents Sea. Larval stages of RKC play an important role in determining the spread and recruitment of the population in the coastal waters. We present a review of studies concerned with the ecology of RKC larvae in the Barents Sea focusing on their dynamics and role in the trophic food webs as well as on the role of environmental factors in driving RKC zoeae. Zoeal stages are larger, and their development time is shorter in the Barents Sea compared to the North Pacific. RKC larvae appear in late January–February and can be found in the coastal plankton until mid-July. Mass hatching of RKC larvae in the Barents Sea starts in late March-early April. The highest densities of RKC larvae are located in small semi-enclosed bays and inlets with weak water exchange or local eddies as well as in inner parts of fjords. Size structures of the zoeal populations are similar in the inshore waters to the west of Kola Bay but slightly differ from those in more eastern regions. RKC larvae perform daily vertical migrations and move to deeper depths during bright daylight hours and tend to rise during night hours. RKC larvae are plankton feeders that ingest both phyto- and zooplankton. A set of environmental variables including food conditions, water temperature, and advective influence are the most important factors driving the spatial distribution, phenology, survival rates, development, growth, and interannual fluctuations of RKC larvae. Recent climatic changes in the Arctic may have both negative and positive consequences for RKC larvae.

Climate Change Will Fragment Florida Stone Crab Communities

Many marine species have been shown to be threatened by both ocean acidification and ocean warming which are reducing survival, altering behavior, and posing limits on physiology, especially during earlier life stages. The commercially important Florida stone crab, Menippe mercenaria, is one species that is affected by reduced seawater pH and elevated seawater temperatures. In this study, we determined the impacts of reduced pH and elevated temperature on the distribution of the stone crab larvae along the West Florida Shelf. To understand the dispersion of the larvae, we coupled the multi-scale ocean model SLIM with a larval dispersal model. We then conducted a connectivity study and evaluated the impacts of climate stressors by looking at four different scenarios which included models that represented the dispersion of stone crab larvae under: 1) present day conditions as modelled by SLIM for the temperature and NEMO-PISCES for the pH, 2) SSP1-2.6 scenario (-0.037 reduction in pH and +0.5°C compared to present-day conditions), 3) SSP2-4.5 scenario(-0.15 reduction in pH and +1.5°C) and 4) SSP5-8.5 scenario (-0.375 reduction in pH and +3.5°C). Our results show a clear impact of these climate change stressors on larval dispersal and on the subsequent stone crab distribution. Our results indicate that future climate change could result in stone crabs moving north or into deeper waters. We also observed an increase in the number of larvae settling in deeper waters (defined as the non-fishing zone in this study with depths exceeding 30 m) that are not typically part of the commercial fishing zone. The distance travelled by larvae, however, is likely to decrease, resulting in an increase of self-recruitment and decrease of the size of the sub-populations. A shift of the spawning period, to earlier in the spring, is also likely to occur. Our results suggest that habitats in the non-fishing zone cannot serve as a significant source of larvae for the habitats in the fishing zone (defined as water depth&amp;lt; 30 m) since there is very little exchange (&amp;lt; 5% of all exchanges) between the two zones. These results indicate that the stone crab populations in Florida may be susceptible to community fragmentation and that the management of the fishery should consider the potential impacts of future climate change scenarios.

Caribbean king crab larvae and juveniles show tolerance to ocean acidification and ocean warming

Coastal habitats are experiencing decreases in seawater pH and increases in temperature due to anthropogenic climate change. The Caribbean king crab, Maguimithrax spinosissimus, plays a vital role on Western Atlantic reefs by grazing macroalgae that competes for space with coral recruits. Therefore, identifying its tolerance to anthropogenic stressors is critically needed if this species is to be considered as a potential restoration management strategy in coral reef environments. We examined the effects of temperature (control: 28 °C and elevated: 31 °C) and pH (control: 8.0 and reduced pH: 7.7) on the king crab’s larval and early juvenile survival, molt-stage duration, and morphology in a fully crossed laboratory experiment. Survival to the megalopal stage was reduced (13.5% lower) in the combined reduced pH and elevated temperature treatment relative to the control. First-stage (J1) juveniles delayed molting by 1.5 days in the reduced pH treatment, while second-stage (J2) crabs molted 3 days earlier when exposed to elevated temperature. Juvenile morphology did not differ among treatments. These results suggests that juvenile king crabs are tolerant to changes associated with climate change. Given the important role of the king crab as a grazer of macroalgae, its tolerance to climate stressors suggests that it could benefit restoration efforts aimed at making coral reefs more resilient to increasingly warm and acidic oceans into the future.

The Effects of Anthropogenic Electromagnetic Fields (EMF) on the Early Development of Two Commercially Important Crustaceans, European Lobster, Homarus gammarus (L.) and Edible Crab, Cancer pagurus (L.)

Proposed offshore windfarm sites could overlap with the brooding and spawning habitats of commercially important crustacea, including European lobster, Homarus gammarus and Edible crab, Cancer pagurus. Concerns have been raised on the biological effects of Electromagnetic Fields (EMFs) emitted from subsea power cables on the early life history of these species. In this study, ovigerous female H. gammarus and C. pagurus were exposed to static (Direct Current, DC) EMFs (2.8 mT) throughout embryonic development. Embryonic and larval parameters, deformities, and vertical swimming speed of freshly hatched stage I lobster and zoea I crab larvae were assessed. EMF did not alter embryonic development time, larval release time, or vertical swimming speed for either species. Chronic exposure to 2.8 mT EMF throughout embryonic development resulted in significant differences in stage-specific egg volume and resulted in stage I lobster and zoea I crab larvae exhibiting decreased carapace height, total length, and maximum eye diameter. An increased occurrence of larval deformities was observed in addition to reduced swimming test success rate amongst lobster larvae. These traits may ultimately affect larval mortality, recruitment and dispersal. This study increases our understanding on the effects of anthropogenic, static EMFs on crustacean developmental biology and suggests that EMF emissions from subsea power cables could have a measurable impact on the early life history and consequently the population dynamics of H. gammarus and C. pagurus.

Larval rearing of orange mud crab, Scylla olivacea: improving survival rate and shortening metamorphosis period

Orange mud crab (Scylla olivacea) is an important aquaculture species in Southeast Asian countries, especially in the Southwest costal region of Bangladesh. Due to unavailability of hatchery produced seeds the farming of S. olivacea in exclusively depends on the wild for small juveniles resulting in exploitation of this species in Bangladesh. The development of proper hatchery techniques considering better understandings related to larval development are needed to increase the survival and growth rate of S. olivacea in hatchery conditions. Therefore, this study aimed to optimize the water treatment strategy for the upgrading of water quality, minimizing mortality and shortening the metamorphosis duration during larval rearing of mud crab. Newly hatched larvae were reared in three different rearing conditions where the water was treated with both prebiotic (Super-TCT-Biotic, 5 ppm) and probiotics (Fish probiotic, 0.5 ppm) in treatment-1 (T1) but only prophylaxis (mixure of 0.025 ppm Teflan and 0.3 ppm Furazolidone) in treatment-2 (T2). In treatment-3 (T3), prebiotic (5 ppm) and probiotics (0.5 ppm) were combinedly used during first 10 days and prophylaxis (0.3 ppm) was also used from day 14 to day 25. The stocking density was maintained as 50 zoea.L-1 and rotifer, liquid rotifer, enriched Artemia and liquid Artemia were used as feed for the larval growth. The findings revealed that hydrological parameters viz., temperature, salinity, pH, dissolved oxygen and ammonia in all the treatments were similar and found within the acceptable ranges for mud crab larvae rearing. The value of larval stage index (LSI) was found significantly higher (p&lt;0.05) on 21st day of rearing in T3 (6.87±0.06) than T1 (6.74±0.04) and T2 (6.61±0.07). Between, zoea1 and crablet phase, the significantly higher survival rate was observed in T3 (7.00±1.00) than T1 (5.00±0.00) and T2 (4.00±1.00). The result of the present study suggested that combined water treatment with prebiotic, probiotic and prophylaxis can shorten the metamorphosis period and enhance the survival rate of S. olivacea.

Effects of Rotifer Feeding Frequency on Growth and Survival Rate of Early Larval Stages of Mud Crab, Scylla olivacea

Crustacean larvae have the characteristics of living as carnivorous organisms. This has an impact on the length of gut evacuation time which affects the feeding pattern of the larvae. The feeding strategy of mud crab larvae is modulated by the length of gut evacuation time. Another factor that can be subject to modulation is the frequency of feeding. This research aimed to evaluate rotifer frequency feeding of early larvae stages of mud crab, Scylla olivacea. This research was conducted at the Mariculture Fisheries Center, Ambon with an indoor system. This research began with carrying out parental maintenance to produce larvae. Larvae are fed with rotifers with different frequencies. The treatments were the frequency of feeding rotifers, namely: Treatment 1 (F1) was the frequency of 1x a day (9:00 am); Treatment 2 (F2) was a frequency of 2x a day (9:00 am &amp; 13:00 pm) and Treatment 3 (F3) was a frequency of 3x a day (9:00am, 13:00pm &amp; 17:00pm). Each treatment was given 3 replications. Based on the results of this study, it showed that feeding with a frequency of three times a day (F3 treatment) was able to have a positive effect on the survival rate of zoea larvae which on the third day was 58% and the fourth day was 22% higher than the F1 and F2 treatments. The growth of larvae showed that F3 treatment was higher than F1 and F2 on the sixth day with an increase in the absolute value of growth of 0.12044 mm compared to F1 of 0.05531 mm and F2 of 0.03253 mm. Keywords: frequency of feeding, growth, larvae, survival rate, mud crab

Seascape genomics identify adaptive barriers correlated to tidal amplitude in the shore crab Carcinus maenas.

Most marine invertebrates disperse during a planktonic larval stage that may drift for weeks with ocean currents. A challenge for larvae of coastal species is to return to coastal nursery habitats. Shore crab (Carcinus maenas L.) larvae are known to show tidal rhythmicity in vertical migration in tidal areas and circadian rhythmicity in microtidal areas, which seems to increase successful coastal settlement. We studied genome‐wide differentiation based on 24,000 single nucleotide polymorphisms of 12 native populations of shore crab sampled from a large tidal amplitude gradient from macrotidal (~8 m) to microtidal (~0.2 m). Dispersal and recruitment success of larvae was assessed with a Lagrangian biophysical model, which showed a strong effect of larval behaviour on long‐term connectivity, and dispersal barriers that partly coincided with different tidal environments. The genetic population structure showed a subdivision of the samples into three clusters, which represent micro‐, meso‐ and macrotidal areas. The genetic differentiation was mostly driven by 0.5% outlier loci, which showed strong allelic clines located at the limits between the three tidal areas. Demographic modelling suggested that the two genetic barriers have different origins. Differential gene expression of two clock genes (cyc and pdp1) further highlighted phenotypic differences among genetic clusters that are potentially linked to the differences in larval behaviour. Taken together, our seascape genomic study suggests that tidal regime acts as a strong selection force on shore crab population structure, consistent with larval behaviour affecting dispersal and recruitment success.

Emerging Diseases and Epizootics in Crabs Under Cultivation

While most crab production for human consumption worldwide comes from capture fisheries, there is increasing production of selected species using aquaculture-based methods. This is both for the purpose of stock replacement and direct yield for human consumption. Disease has limited the ability to produce larval crabs in commercial hatcheries and this together with suitable feeds, are major hurdles in the sustainable development of cultivation methods. Juvenile and adult crabs are also subject to a range of diseases that can cause severe economic loss. Emerging pathogens/parasites are of major importance to crab aquaculture as they can cause high levels of mortality and are difficult to control. Diseases caused by viruses and bacteria receive considerable attention but the dinoflagellate parasites,Hematodiniumspp., also warrant concern because of their wide host range and lack of control methods to limit their spread. This concise review examines the emerging diseases in several crabs that have been selected as candidates for aquaculture efforts including Chinese mitten crabs (Eriocheir sinensis), mud crabs (Scyllaspp.), swimming crabs (Portunusspp.), blue crabs (Callinectes sapidus) and shore crabs (Carcinus maenas). The latter is also a prolific invasive species known to harbour diverse macro- and micro-parasites that can affect commercially important bivalves and crustaceans.