Perisesarma Bidens Research Articles

Contrasting population genetic structure of three semi‐terrestrial brachyuran crabs on the coast of the Japanese archipelago

AbstractAnthropogenic activities have reduced ecotones between the ocean and land, which is likely to threaten the population of brackish‐water brachyuran crabs. To assess the current status of these crabs, we examine the population genetic structures of three semi‐terrestrial brachyuran crabs widely distributed along the coast of the Japan and to clarify factors determining their genetic structures. We collected 184 Orisarma dehaani, 252 Chiromantes haematocheir, and 151 Helice tridens crabs from 36 localities of the Japanese archipelago. Genome‐wide SNP data from these crabs were analyzed using MIG‐seq. Bayesian clustering of STRUCTURE and DAPC analysis were used to identify genetically disturbed populations and to visualize genetic differentiation between local populations. Genetic population structure showed clear differentiation between populations on the Pacific coast of the Tohoku region and on other Japanese coasts in O. dehaani, but not in C. haematocheir or H. tridens. The inbreeding coefficient of O. dehaani was significantly higher on the Pacific coast of the Tohoku region compared to other Japanese coasts. C. haematocheir and H. tridens had homogeneous genetic structures along the Japanese coast, but showed genetic differentiation of a local population at their range limits. Thus, O. dehaani showed little gene flow and clear genetic differentiation between populations in the Tohoku Pacific region and those on other Japanese coasts due to ocean currents. Although such a regional differentiation was not found in C. haematocheir and H. tridens, one population of C. haematocheir was genetically isolated at the edge of its distribution range and likely vulnerable to environmental changes.

Conserved organ-specific microbial assemblages in different populations of a terrestrial crab.

Microorganisms are ubiquitous in the environment and provide genetic and physiological functions to multicellular organisms. Knowledge on the associated microbiota is becoming highly relevant to understand the host's ecology and biology. Among invertebrates, many examples of endosymbiosis have been described, such as those in corals, ants, and termites. At present, however, little is known on the presence, diversity, and putative roles of the microbiota associated to brachyuran crabs in relation to their environment. In this work we investigated the associated microbiota of three populations of the terrestrial brachyuran crab Chiromantes haematocheir to find evidence of a conserved organ-specific microbiome unrelated to the population of origin and dissimilar from environmental microbial assemblages. Bacterial 16S rRNA gene and fungal ITS sequences were obtained from selected crab organs and environmental matrices to profile microbial communities. Despite the presence of truly marine larval stages and the absence of a gregarious behaviour, favouring microbiota exchanges, we found common, organ-specific microbiota, associated with the gut and the gills of crabs from the different populations (with more than 15% of the genera detected specifically enriched only in one organ). These findings suggest the presence of possible functional roles of the organ-specific microbiota.

Dietary effects on larval survival and development of three sesarmid crabs

Semi-terrestrial brachyuran sesarmid crabs are the most diverse and important faunal components of mangrove forest and temperate coastal communities worldwide. To establish a stable larval rearing method for understanding their larval developmental processes including molecular mechanisms of molting and metamorphosis, we examined the effects of diet on the survival and growth of three sesarmid crabs, Chiromantes haematocheir, Orisarma intermedium, and O. dehaani under larval development. Zoea of each species, immediately after hatching, were reared under different feeding conditions as follows: non-feeding; fed only nutrition-enriched rotifers; fed only Artemia (brine shrimp) nauplii; and fed a combination of both nutrition-enriched rotifers and brine shrimp. Larvae of each species survived almost to megalopa when they were fed both rotifer and brine shrimp, but all C. haematocheir larvae had died by zoeal stage 2 when they were only fed brine shrimp. Chiromantes haematocheir larvae could survive into the megalopa stage when fed only nutrition-enriched rotifer, whereas both O. dehaani and O. intermedium showed 50% or less survival and metamorphosis rates into megalopa. The duration of larval development and survival rates of the three crabs were shorter and higher, respectively, in the mixed feeding group (both rotifer and brine shrimp) than when only fed rotifer or brine shrimp. This study provides baseline knowledge of the interspecific variability in larval survival and duration under different diets for sympatric sesarmid crab species.

Coastal Forest Structure Survey and Associated Land Crab Population in Suao Dakenggu Community, Yilan, Taiwan

Coastal forests can increase the resilience of seaside communities against natural disasters. These forests also provide other benefits, including food and an avenue for economic growth. The Dakenggu community in Suao, Yilan (Taiwan), is adjacent to a coastal forest with an area of nearly 114,000 m2. Artificial plantation has been performed locally in this area since 1977 to prevent the loss of beaches. The coastal forest area was estimated through drone aerial photography combined with a geographic information system. We found that Pandanus tectorius (11.5%), Casuarina equisetifolia (30.8%), Cerbera manghas (4.07%), Hibiscus tiliaceus (5.2%), and grass (23.52%) are the dominant species in the plant community of Dakenngu coastal forest, which together accounted for 75.1% of the total land area. The area covered by different species in the coastal forest was examined and estimated as well. The height and diameter at breast height (DBH) of the main tree species in five transects were surveyed, and we also found some significant differences among transects that correspond to cohorts planted at different times by the Forestry Bureau. We also performed a survey of land crabs in the same transects over five months to infer any differences in land crab species among the transects. We found that the transect dominated by H. tiliaceus had a larger population of land crabs than others. We revealed that the mudflat crab Chiromantes haematocheir prefers to live under H. tiliaceus. Finally, we propose recommendations for improving the biodiversity of the Dakenggu coastal forest so that it can become a sustainable resource for its residents.

Seaward Migration and Larval Release Coincide with Lunar and Light-dark Cycles in Supratidal Land Crabs Cardisoma carnifex and Epigrapsus notatus.

Herein we investigated the synchronous breeding migration and larval release of ovigerous females in two dominant supratidal land crabs Cardisoma carnifex and Epigrapsus notatus in the mixed semidiurnal tidal regime in Taijiang National Park (Tainan, Taiwan). We mainly focused on the monthly and daily rhythms during the breeding season of migration and larval release for these two crabs. We also sought to understand what the main environmental cues were for these monthly and diel rhythms. Both lunar and tidal amplitude cycles are potential proximate causes for the monthly lunar/semilunar reproductive rhythm in crabs. Likewise, either the 24-hour (diel) light cycle or tidal cycle can act as the proximate cause for diel reproduction rhythm, and we investigated which one was the main factor that entrains the diel rhythm for these two species. We found that the season of migration and larval release in C. carnifex occured mainly between June and September during the rainy season while those of E. notatus occurred mainly between September and October, near the end of the rainy season. Regarding the rhythm of migration and larval release in monthly time scale, C. carnifex exhibited a semilunar rhythm following the syzygies and E. notatus exhibited a lunar rhythm following the full moon. However, these rhythms did not occur with the maximum amplitude nocturnal and diurnal high tides. This implies that the lunar cycle is a more important environmental cue than the tidal amplitude in the entrainment of the synchronous monthly breeding rhythm for these two species. This pattern is different from other intertidal crabs, most of which use the tidal amplitude cycle as the main environmental cue for larval release. In addition to Chiromantes haematocheir (a supratidal crab), our study provided two more species that live in the supratidal zone time their reproduction with respect to the lunar light cycle and independent of the tide amplitude cycles. For the diel rhythm, both species migrated to the shore and released larvae in the first half of the night during the flood tide. This suggests that the diel light cycle is a dominant cue for the determination of larval release timing for these two species. Larval release does not track the high slack tides, since larvae are only released during the first half of the night and these high slack tides occur only after midnight (0000-0600H) during the days of larval release for these two crab species.

Fluorene is Highly Toxic to Zoea Larvae of the Red-Clawed Crab Chiromantes haematocheir

Fluorene is Highly Toxic to Zoea Larvae of the Red-Clawed Crab Chiromantes haematocheir

The Relationship between Population Density and Body Size of the Giant Mountain Crab Indochinamon bhumibol (Naiyanetr, 2001), an Endangered Species of Freshwater Crab from Northeastern Thailand (Potamoidea: Potamidae)

The giant mountain crab (Indochinamon bhumibol) is endemic to Loei Province in north-eastern Thailand. Although, little knowledge is available on the factors affecting population dynamics and individual fitness. This study aimed to investigate the relationship between the population density and body size of the crab. The mark–recapture method was conducted in Phu Ruea National Park (PR, small area) and Phu Luang Wildlife Sanctuary (PL, large area) between February 2018 and January 2019. The crabs inhabited mountain streams at 400–1100 m. The average water depth and width were 0.6 m and 8.3 m, respectively. In total, 879 individuals were caught from PL compared to 583 individuals from PR. Male were more abundant than female in both areas. Male were also larger and heavier, with a mean weight of 145 g, mean carapace width of 76 mm and mean carapace length of 75.7 mm. The average number of crabs caught was higher in the rainy season (66.3 individuals). The crab population was larger in PL (256.7 individuals), which is bigger in size than PR and is located farther from urban areas. The average crab density in PL and PR were 1.7 and 1.6 crabs/m2, respectively. Population density was significantly correlated with body size parameters: body weight (r2 = 0.066, df = 1196, p < 0.001), carapace width (r2 = 0.053, df = 1196, p < 0.001) and carapace length (r2 = 0.067, df = 1196, p < 0.001). The findings of this study suggest that a large area size and high population density are important to the conservation of the giant mountain crab in mountainous forests.

De novo transcriptome assembly of the midgut glands of herbivorous land crabs, Chiromantes haematocheir, and identification of laccase genes involved in lignin degradation.

Herbivorous land crabs such as Chiromantes haematocheir and C. dehaani show biomass-degrading activities. In this study, we performed RNA-seq analysis to detect biomass-degrading enzymes. A de novo transcriptome assembly in the midgut glands of molting and non-molting C. haematocheir crabs was constructed using RNA sequencing. Illumina sequencing generated 44,937,002 and 44,394,310 reads from the two midgut glands. In total, 178,710 contigs with an average length of 750bp and an N50 value of 1,235bp were assembled, of which 37,890 contigs were annotated using BLASTx search against the NCBI database. We identified 22 contigs (11 genes) belonging to the laccase family and 44 contigs (22 genes) belonging to the peroxidase family. Sixteen contigs (three genes) belonging to the GH9 cellulase family were also detected. We selected the gene accounting for the majority of expressed laccase and analyzed its properties. The 24131-laccase transcript (2465bp) had one complete open reading frame, nt 149-1987, encoding a protein of 613 amino acids with a deduced molecular mass of 67.708kDa. The enzyme was shown to belong to the multicopper oxidase family. The 24131-laccase protein was confirmed to have oxidation activity against 2,6-dimethoxyphenol by ectopic expression in Escherichia coli. Laccase activity was significantly enhanced by feeding land crabs with plant diets. These data suggest that the enzyme plays an important role in the digestion of lignin in the guts of land crabs.

Settlement patterns of two sesarmid megalopae in the Sai River Estuary, Ishikawa Prefecture, Japan

Two semi-terrestrial crab species, Chiromantes haematocheir and Chiromantes dehaani, are closely related and have a sympatric distribution. The ecological characteristics of these species, including habitat and behavior during the adult stage, have been investigated. However, the larval stage remains poorly understood because it is difficult to identify larvae morphologically. Our study objectives are to clarify the settlement patterns involved in recruitment of the two species of megalopae using genetic analysis and the effects of ecological factors on settlement, including 1) seasonal changes, 2) spatial variations (dominated by conspecific or heterospecific adults), and 3) tidal effects. The Chiromantes megalopae were collected in the lower reach of the Sai River during spring and neap tides from August to November 2017. Megalopa larvae were collected from three areas: one dominated by C. haematocheir adults, one dominated by C. dehaani adults, and a revetment area. Both species of megalopae showed seasonal and spatial variations in settlement, which also differed with tidal fluctuations. Chiromantes dehaani megalopae settled from mid-August to early October and C. haematocheir megalopae settled from early September to early November. Chiromantes haematocheir megalopae preferentially settled in the area dominated by conspecific adults over the area dominated by C. dehaani and the revetment area, while no difference in the settlement of C. dehaani megalopae was observed among areas. Chiromantes haematocheir megalopae returned on the spring tide; however, C. dehaani megalopae showed no tidal pattern.

Comparative Mitochondrial Genome Analyses of Sesarmid and Other Brachyuran Crabs Reveal Gene Rearrangements and Phylogeny.

Mitochondrial genomes (mitogenomes) are important for understanding molecular evolution and phylogenetic relationships. The complete mitogenome of Perisesarma bidens was determined, which is 15,641 bp in length. The A + T content of P. bidens mitogenome was 74.81%. The AT skew was slightly negative (−0.021). The 22 tRNAs ranged from 65 to 73 bp and were highly A + T biased. All tRNA genes had typical cloverleaf structures, except for the trnS1 gene, which lacked a dihydrouridine (DHU) arm. The gene order within the P. bidens mitogenome was identical to the pancrustacean ground pattern, except for the translocation of the trnH. Additionally, the gene order of trnI-trnQ-trnM in pancrustacean ground pattern became trnQ-trnI-trnM in P. bidens. Phylogenetic analyses supported the inclusion of P. bidens in Sesarmidae and the promotion of Sesarminae to Sesarmidae. The results will help us to better understand the status and evolutionary history of Grapsoidea crabs.

Bioactive Indolyl Diketopiperazines from the Marine Derived Endophytic Aspergillus versicolor DY180635.

Four new indolyl diketopiperazines, aspamides A–E (1–4) and two new diketopiperazines, aspamides F–G (5–6), along with 11 known diketopiperazines and intermediates were isolated from the solid culture of Aspergillus versicolor, which is an endophyte with the sea crab (Chiromantes haematocheir). Further chiral high-performance liquid chromatography resolution gave enantiomers (+)- and (−)-4, respectively. The structures and absolute configurations of compounds 1–6 were determined by the comprehensive analyses of nuclear magnetic resonance (NMR), high-resolution mass spectrometry (HR-MS), and electronic circular dichroism (ECD) calculation. All isolated compounds were selected for the virtual screening on the coronavirus 3-chymoretpsin-like protease (Mpro) of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), and the docking scores of compounds 1–2, 5, 6, 8 and 17 were top among all screened molecules, may be helpful in fighting with Corona Virus Disease-19 (COVID-19) after further studies.

Guaiacol oxidation activity of herbivorous land crabs, Chiromantes haematocheir and Chiromantes dehaani

The land crabs, Chiromantes haematocheir (Akate-gani) and Chiromantesdehaani (Kurobenkei-gani) inhabit seaside forests in Japan. The crabs mainly consume plant material and its detritus. Therefore, they are expected to possess the ability to degrade the major components of biomass, cellulose and lignin in order to digest plant materials. In this study, we analyzed biomass-degrading activities of the land crabs, especially guaiacol oxidation activity, which seems to be related to lignin degradation. Cellulase activity was detected from almost all gut samples including the stomach, midgut gland and intestine of all dissected crabs. Conversely, high guaiacol oxidation activity was detected in the midgut gland of all C.dehaani and several female C.haematocheir crabs. This is consistent with a previous study showing that female crabs were more herbivorous than male crabs were and observation that C.dehaani crabs are more herbivorous than C.haematocheir. Guaiacol oxidation activity might play an important role in the herbivorous behavior of land crabs.

Relationship between Environmental Improvement and Occurrence of <i>Chiromantes haematocheir</i> in a Park on a Reclaimed Shore

Sennan Satoumi Park on a reclaimed shore has attempted to improve coastal forest environment and constructed a new ecological path that connects coastal forest to shore for conservation of Chiromantes haematocheir. However, the effects of environmental improvement after 2008 on occurrence of the crabs along the coastal forest were unclear. Therefore, we compared change of occurrence, and identified effects brought by the environmental improvement. The results indicated that the path and the environmental improvement in the coastal forest had positive effects on number and range of occurrence of crabs. On the other hand, we found that spatially continuous dry sections along the coastal forest were obstructions of movement of crabs.As we confirmed that crabs have relatively high ability to migrate in daily activity, improvement of the dry sections for migration of crabs is recommended in order to mitigate impacts of predators and disasters. Ecological path and the environmental improvement in the coastal forest implemented in the present study site may be effective to enhance movement of crabs in a park on a reclaimed shore.

The complete mitochondrial genome of red-clawed crab Chiromantes haematochir (Sesarmidae: Grapsidae)

The complete mitogenome of Chiromantes haematocheir is 15 899 bp in length contains the typical set of 37 genes, including 13 protein-coding genes (PCGs) (ATP6, ATP8, COI-III, ND1-6, ND4L, and Cyt b), two rRNAs (12S rRNA and 16S rRNA), 22 tRNAs, and a putative CR (D-loop). All PCGs start with an ATG codon except ND1 start with ATT and ND3 start with ATA. TAA is the most frequent stop codon, although COI end with TA-, and COII stop with the single nucleotide T-. The new mtDNA sequence contains 12S rRNA and 16S rRNA of rRNAs, separated with tRNAval. All tRNAs possess the typical clover leaf secondary structure except for tRNASer(AGN) and tRNALeu(CUN), which lacks a dihydroxyuridine (DHU) arm. The CR is 826 bp in length, located between 12S rRNA and tRNAGlx. The phylogenetic trees support Chiromantes haematochir has close relative with Sesarmops sinensis and Sesarmane glectum.

Invasive Smooth Cordgrass (Spartina alterniflora) Eradication and Native Crab Recovery

AbstractInvasive smooth cordgrass (Spartina alterniflora Loisel) eradication is important for the health of many coastal ecosystems. An integrated regime of continuous submergence after clear mowing, with three interval levels between mowing and submergence (5, 10, and 15 d) and three submergence depths (20, 30, and 50 cm), was implemented in cofferdams enclosing invader populations along a Chinese coast. In July of the following year, after the roots of mowed S. alterniflora had been submerged for 12 mo, some ramets grew under the regime with an interval of 15 d and the regime with a submergence depth of 20 cm, but no ramets occurred under the regimes with submergence depths of 30 or 50 cm and intervals of 5 or 10 d. Four crab species were documented: Helice tridens tientsinensis Rathbun, Sesarma dehaani H. Milne-Edwards, Ocypode stimpsoni Ortmann, and Chiromantes haematocheir de Haan. Biomass and abundance values of crab species in the cofferdams were similar to those in the mudflats but different from those in smooth cordgrass populations. Thus, the treatment of submergence after mowing, which was implemented in the cofferdams, can control S. alterniflora and provide a mudflat-like habitat that promotes crab recovery if this treatment uses the proper combination of submergence depth and interval between mowing and submergence.

A comprehensive phylogenetic analysis of Grapsoidea crabs (Decapoda: Brachyura) based on mitochondrial cytochrome oxidase subunit 1 (CO1) genes

The sequences of mitochondrial cytochrome c oxidase subunit I (CO1) genes of eight species crabs of Grapsoidea were determined and analyzed in this paper. The traditional classification is that Grapsidae contains four subfamilies comprising Grapsinae, Varuninae, Sesarminae, and Plagusiinae, which are also treated as families in some studies. There is a lack of clarity in the classification of some species, such as Eriocheir species. In this study, we conducted the first exploration of evolutionary relationships among species based on analysis of the molecular data of CO1 genes of eight species (Sesarmops sinensis, Clistocoeloma sinensis, Perisesarma bidens, Helice latimera, Helice tientsinensis, Helice wuana, Hemigrapsus sanguineus, and Varuna litterata). We provide a detailed and comprehensive view of the phylogenetic relationships of the Grapsoidea species determined by maximum likelihood and Bayesian inference analyses. The results show that S. sinensis, C. sinensis, and P. bidens are part of Sesarmidae, Grapsoidea, while H. latimera, H. tientsinensis, H. wuana, H. sanguineus, and V. litterata belong to Varunidae, Grapsoidea. The results revealed that Varunidae should be monophyletic and Sesarmidae should be paraphyletic.

Microhabitat differences in crab assemblage structures in a subtropical mangrove estuary on Iriomote Island, southern Japan

Crab assemblage structures in sandy flat, muddy flat and mangrove forest microhabitats in a mangrove estuary of the Urauchi River, Iriomote Island, southern Japan, differed clearly among the three microhabitats, species and individual numbers being greater inside the mangrove forest than on the flats. A similarity index showed distinct differences in species composition among the microhabitat assemblages, primarily due to the differential distributions of dominant species, such as the soldier crab Mictyris guinotae, sentinel crab Macrophthalmus convexus and sesarmid crab Perisesarma bidens. A canonical correspondence analysis indicated that the differences likely arose from among-microhabitat differences in the physical environment, the mangrove forest being characterized mainly by structurally complex mangrove roots, lower soil porewater temperatures and higher relative substrate elevation, the sandy flat by lower organic content of the sediment and higher porewater oxygen amount, and the muddy flat by higher levels of sediment water and organic material. The findings suggested that microhabitat-related physical differences are important factors determining crab distribution patterns in mangrove estuaries.

Pollution-, temperature- and predator-induced responses in phenotypically plastic gastropod shell traits

ABSTRACTPhenotypically plastic traits adopt different appearances in different environments. Researchers routinely investigate environmental variables such as humidity and temperature as influential factors, but predation also can influence phenotype. Gastropods include well-known examples where predation, even if only perceived, can produce shell morphology changes. We conducted a quantitative descriptive study to investigate how apple snail (Pomacea bridgesii) shells changed in response to red-clawed crab (Perisesarma bidens) predator presence when snails were forced to cope with increased pollution levels in water from an industrialised bay in Lake Ontario (Hamilton Harbour, Ontario, Canada). Compared to snails in unpolluted predator-free water, snails in unpolluted predator-containing water grew large thick shells with small apertures; shape differences were produced with relatively tightly coiled, elongated shell apertures. Snails in highly polluted predator-containing water produced thick shells that, contrastingly, changed from relatively short and wide to relatively long and narrow during growth. Antipredator responses that are evoked by waterborne chemical signals thus can be altered by environmental pollutants.

Chemical changes in detrital matter upon digestive processes in a sesarmid crab feeding on mangrove leaf litter

Pathways and rates of decomposition of detrital matter partly depend on its chemical composition. Digestive processes of detritivores drive changes in the chemical composition of detritus, and these changes translate into the chemical composition of the organic matter sequestered into soils and sediments. The latter, in turn, determines how stable organic matter stocks are towards further decay and release of climate-active gases thereupon. We used metabolic fingerprinting to monitor changes in the chemical composition of mangrove detritus upon digestion by a mangrove crab. According to analyses through pyrolysis-GC/MS, the decaying leaf litter of three mangrove species of the Indo-West Pacific, Bruguiera gymnorhiza (L.) Savigny ex Lam. and Poiret 1798, Ceriops tagal (Perr.) C.B. Robinson 1908, and Rhizophora mucronata Lam. 1804, clearly differed from each other in their chemical signature. The feces of detritivorous crabs (Sesarma bidens de Haan 1835) feeding on these detrital sources differed from the source litter in their chemical composition, obviously owing to digestive processes. However, the chemical signatures of feces were more similar to those of their source litter than to those of feces from different litter sources, indicating that the origin of organic matter can be tracked in fecal material. Moreover, male and female crabs appear to exhibit sex-specific digestive processes, as they produced feces that clearly differed from each other in their chemical signature. The 15 chemical compounds most relevant for distinguishing litter sources and fecal material provide first hints on which compounds discriminate the different tree species and characterize digestion by S. bidens. For instance, coumaran (dihydro-benzofuran), indicative of certain carbohydrates, was abundant as a pyrolysis product of the litter of R. mucronata and, to a much lesser degree, C. tagal. Hence, the carbohydrates that were pyrolysed into coumaran seem to discriminate the former two litter sources. Similarly, a pyrolysis-derivate of plant phenolics or proteins, discriminated C. tagal from the other litter sources. From this, we conclude that even subtle differences in litter chemistry and digestive processes of detritivores can be characterized and followed with high resolution through (py-)GC/MS. Further, we propose that the origin of fecal material can be identified with the aid of this technique, and we are currently studying whether the origin of organic matter in the sediment can also be inferred from (py-)GC/MS-data.

Moulting of the semi-terrestrial crab Chiromantes haematocheir (De Haan, 1833) (Decapoda, Sesarmidae) in Taiwan

Population structure and moulting of the semi-terrestrial crab Chiromantes haematocheir (De Haan, 1833) were studied in Taiwan. The crab moults nocturnally in small freshwater pools, and newly moulted crabs and cast integuments were used to assess moult increment. Males reached a larger size (max. CW 36 mm, ) than females (max. CW 33 mm, ): from 22 mm CW males increasingly dominated the population. Size at maturity was estimated at 17.5 mm CW. The percentage moult increment averaged 11.5% in males (5.5-19%, ) and 13.9% in females (7-23%, ). Female increment exceeded male increment for all overlapping size classes. The larger size of mature males, despite a smaller percentage increment, is explained by a higher post-puberty moult frequency. Of the moulting crabs, 25% of males and 38% of females had one or more missing or regenerating peraeopods. In both sexes this reduced the percentage increment, more so the larger number of limbs affected. The moulting conditions for C. haematocheir are not ideal, with constraints in relation to calcium supplies, and shelter. So the moult increments are unsurprisingly less than those of shallow water marine crabs moulting in an optimal environment, but larger than those of land crabs moulting without access to standing water.