Crab Species Research Articles

Heterochely and handedness in the orange mud crab Scylla olivacea: implication for future culture practice optimisation.

Asymmetric body traits in bilateral organisms are common and serve a range of different functions. In crustaceans, specifically among brachyuran crabs, heterochely and handedness in some species are known to aid in behavioural responses such as food acquisition, and sexual and territorial displays. However, the heterochely of the intertidal mud crab genus Scylla is still poorly understood. This study investigated the cheliped morphometric characteristics of orange mud crab Scylla olivacea and the relation of heterochely and handedness to sex. Scylla olivacea is heterochelous, with predominant right-handed (70.2%). Three morphometric variables, i.e., propodus length (PL), propodus depth (PD), and propodus width (PW) were significantly larger in the right cheliped and the estimated handedness based on these three variables were consistent with the presence of molariform teeth. The effect of sex had no influence on the occurrence of heterochely or handedness. The frequency of left-handedness increased with size, especially in males. We postulate that handedness reversal, a phenomenon seen in other crab species when the dominant hand is lost, also occurs in S. olivacea, thereby resulting in a change in left-handedness frequency. The use of chelipeds by males in mate and territorial defenses might provide an explanation for the higher risk of losing a dominant cheliped and thus, higher left-handedness frequency compared to females. Future behavioural research could shed light on the selective forces that affect the handedness distribution in mud crabs. Knowledge on heterochely and handedness of mud crabs could be useful for future development of less aggressive crab populations by claw reversal and the optimisation of limb autotomy techniques.

Insights into the Gut Microbiota of the Freshwater Crab Sinopotamon planum across Three Seasons and Its Associations with the Surrounding Aquatic Microbiota

Gut microbiota is closely related to the health of the host and its adaptation to environmental changes. Sinopotamon planum is a species of freshwater crab that lives in the water for three seasons and plays a key role in freshwater ecosystems as a benthic macroinvertebrate, an important indicator of aquatic ecological health. In this study, we sequenced 60 gut microbial samples of S. planum and nine microbial samples from the surrounding water in spring, summer, and autumn based on the 16S rRNA gene. The results showed that gut microbiota had the highest alpha diversity in summer, which may be related to increased adaptability in summer. Firmicutes, Proteobacteria, and Bacteroidota were the most dominant phyla of gut microbiota across three seasons, with Candidatus Hepatoplasma and Candidatus Bacilloplasma being the main genera. These main phyla and genera may be key to maintaining a stable function of the intestinal environment. Firmicutes was the phylum with the highest relative abundance, which is probably related to the carnivorous behaviour of S. planum. The abundant C. Hepatoplasma may be related to the starvation of S. planum in the wild. In both gut and water microbiota, beta diversity analyses showed significant differences across seasons. Comparative analysis of gut microbes and surrounding water microbes showed significant differences in microbial diversity and composition between gut and surrounding water. In conclusion, the structure of the gut microbial community of S. planum differed significantly between the studied seasons, but the water microbial community around S. planum was less variable and significantly different from the gut microbes. The seasonal differences in gut microbes are more likely the result of self-internal adaptation to changes in water temperature and food resources between seasons.

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.

Global Distribution of Brachyuran Crabs in Mangroves

The present work has compiled a total of 389 brachyuran crab species belonging to 188 genera and 38 families to be present in mangrove forests across 122 countries/territories in 10 sub-regions of two global hemispheres viz., Indo-West Pacific (IWP) and Atlantic East Pacific (AEP). The mangrove crabs are highly diverse in the IWP as compared to AEP. They exceed 100 species in nine countries of the IWP viz., Indonesia, India, Japan, Thailand, Australia, Singapore, Philippines, Malaysia, and China. The least number of mangrove crab species (> 10) are found to be present in 38 countries under the AEP. Four countries/territories do not have any record of mangrove crabs. Sesarmidae is the predominant family of mangrove crabs, followed by Ocypodidae and Portunidae. The present work also has brought out 818 synonyms, which otherwise interfere with the preparation of a checklist for an exact number of crab species. It is a matter of necessity to conserve the crabs, which are keystone species of the mangrove ecosystems.

Study on aquatic biodiversity and its conservation from Banshelki Dam, Udgir Dist. Latur (M.S.)

Banshelki Dam is the fresh water Dam of village Banshelki, near Udgir. It is the good source of biodiversity of aquatic animals in Udgir taluka. About 50 species of plankton, 36 species of crustaceans, are found in the Dam. A total of 100 species of fishes, 20 species of prawns/shrimps and 15 species of crabs are recorded from Dam. The Dam serves many species of aquatic birds during winter season. There are 05 species of amphibians and 15 species of reptiles and 6 species of mammals are found in the Dam. The fish production is fluctuating from year to year. The fish production was higher during 2018-19 and lowest was observed during 2019-2020. The highest crabs were observed to be 1 mt. during 2019-20. The minimum growth rate was observed in the year 2018-19.

Description of unique live colour patterns as a tool for discriminating hermit crab species in the Iberian Peninsula

The unique colour patterns of the hermit crab species inhabiting the Iberian Peninsula and geographically close areas are studied based on colour patterns observed in live specimens either in the field or live in the laboratory. Live colour patterns are shown to be useful for differentiating species in the Paguroidea from Iberian waters. Colour information has not been frequently documented in previous studies, mainly because of difficulties in accessing live specimens. Up to 51 species are currently recorded within the study area, 45 of which are included in the present work, focusing on the distinctive colour traits for each species that can be observed in the field. A complete key for identifying the species within the study area based on colour patterns is included. This study is the first attempt to put in place this type of tool oriented to field work. Further studies will be required to complete and update this information, especially for species which are scarce or difficult to observe alive.

Biocompatibility of crab shell-derived graft sterilized by ultraviolet light towards human gingival fibroblast cell culture

Background: Portunus pelagicus crab species meat is generally taken, and their shells that is thrown away becoming untapped waste. Their shells contain so many useful minerals such as calcium carbonate ­which can be processed into hydroxyapatite (HA). HA has been extensively used in the medical field for bone grafting, to repair damaged in bone structures. Purpose: To determine the biocompatibility of hydroxyapatite from Portunus pelagicus crab’s shells extract after sterilized using UV on human gingival fibroblast cell. Methods: This research is an experimental laboratory research using post-test only control group design. The shells were first heated using furnace. Once hydroxyapatite was obtained, it was sterilized using ultraviolet (UV) with certain concentration (25 ppm, 50 ppm, and 100 ppm) to kill the microorganisms. MTT assay was done to test the biocompatibility of the sterilized hydroxyapatite on human gingival fibroblast cell. Results: The highest viability of fibroblast cells was the group with 50 ppm UV (98.10%), followed by 100 ppm UV (97.93%), and 25 ppm (93.28%). Conclusion: Hydroxyapatite from Portunus pelagicus crab’s shells extract sterilized using UV is biocompatible towards human gingival fibroblast cell.

COI Gene Analysis of Asian Horseshoe Crab in Banyuasin Estuarine Waters, Sumatra, Indonesia

There is limited study on DNA barcoding of horseshoe crabs in South Sumatra, Indonesia. The present study was the first to record horseshoe crabs' COI DNA barcoding in three localities of Banyasin estuarine waters. The nucleotide composition was in a strong adenine thymine bias (AT = 63.90%) with high haplotypic diversity (Hd = 0.858) relative to low nucleotide diversity (π = 0.0534). A total of 16 haplotypes were recorded, of which two were in Carat Cape, 4 in Makati Jaya, and 12 in the Banyuasin river estuary (BRE), and Hap 1 was a dominant type (62.5%). The population differentiation (FST) value was varied, and only in the comparison of BRE-Carat Cape was significant (FST = 0.637), while the gene flow (Nm) value in Makati Jaya-BRE was high (6.563). The neutrality test, Tajima's D (0.4142), and Fu's Fs values were negative (-0.492), suggesting these populations have experienced a current bottleneck or multiplication. Analysis of molecular variation (AMOVA) suggested that 68% was distributed within populations. The haplotype network, PCoA, and phylogenetic of COI DNA sequences clustered in three groups correspond to Carcinoscorpius rotundicauda, Tachypleus gigas, and Tachypleus tridentatus. This finding is a matter of concern for managing and conserving horseshoe crab species in Banyuasin estuarine waters.

Population Structure of Parasesarma brevicristatum and Parasesarma semperi as an Indicator of Mangrove Replanted Forest Condition in Bintuni Bay, Indonesia

The mangrove forest at Bintuni Bay is one of the largest in Indonesia, and a portion of it is being used as production forest to produce woodchips. Replanting in the production forest results in various ecosystem conditions through ages. Since the Sesarmidae crab is an important component of the mangrove ecosystem and contributes significantly to its energy cycle, it is frequently used as a bioindicator to evaluate the ecosystem’s health. In the production mangrove area of Perseroan Terbatas Bintuni Utama Pure Wood Industries, sampling was done using the purposive sample method with circular plots in natural mangrove forests, replanted trees aged 25 and 5 years, and forests that had just been harvested. According to the survey, station 3′s five-year-old replanting of P. brevicristatum and P. semperi crabs had a population density of 139,455 Ind.ha−1 while station 4′s damaged forest had a population density of 119,047 Ind.ha−1. Both varieties of crabs have a higher male to female sex ratio. It was discovered that young individuals dominated the two species of crabs’ size distribution. Both species of crabs’ length weight relationships displayed a positive allometric tendency. The density of the saplings was the element of the mangrove vegetation that had the greatest impact on the population structure of both crabs.

Extraction and Purification of Bioactive Peptide with Antimicrobial Properties from Horseshoe Crab

Abstract: Peptides are small biomolecules that act as bioactive or host defense molecules. These peptides have a significant role in medicine because of their broad spectrum antimicrobial properties. Marine sources are the largest supply of peptides and natural small molecules since they represent half of the total global biodiversity. Among the different crab species, the horseshoe crab is widely used for extracting the peptides. The horseshoe crab is a marine and brackish water arthropod; it plays a crucial role in the reel and whelk fishing industry and the production of important pharmaceutical bioactive components. This review highlights the details of the extraction and purification of antimicrobial peptides from the horseshoe crab. These peptides represent trends and opportunities for the future, with a focus on the pharmaceutical industries.

Sharing is living: The role of habitat heterogeneity in the coexistence of closely related species.

In biologically diverse ecosystems, an essential process to support competing species to coexist is ecological differentiation. Habitat heterogeneity is, hence, important in establishing species abundance and richness, favoring the coexistence of species due to habitat partition. In this context, shading and species thermal tolerance can be good factors to elucidate the role of habitat heterogeneity in the habitat partition among closely related species. Herein, we study shading effects in microhabitat selection, behavior, and physiological limitation on two species of fiddler crabs (Leptuca leptodactyla and Leptuca uruguayensis). Indeed, shading conditions influenced fiddler crabs species proportion over time, with L.leptodactyla more associated with nonshaded/warmer areas while the L.uruguayensis to shaded/cooler ones. They also adjusted their behavior differently from each other to deal with thermal stress. Finally, we have demonstrated that these effects are related to species' physiological limitations. We conclude that biologically diverse ecosystems, such as intertidal regions from estuaries (e.g., mudflats and mangroves), support the coexistence between closely related species by reducing competition due to habitat partition.

Population structure analysis of mangrove mud crab Scylla serrata (Decapoda: Portunidae) from Indian coastal waters

Scylla serrata (Forskal, 1775) is an important crab resource for aquaculture and coastal fisheries in India. Study on population differentiation and population history of this economically important crab species is very much essential for conservation and management. Wild S. serrata samples were collected from 18 different locations in India including Andaman coastal waters. Population structure and demographic history of S. serrata was evaluated using 425bp of cytochrome b and 562bp of 16S rRNA genes. Only nine and three haplotypes were obtained by the analysis of cytochrome b and 16S rRNA gene respectively. Low level of haplotype diversity, nucleotide diversity, non significant F ST values for16S rRNA gene (F ST = 0.0133) and negative non significant F ST values for cytochrome b gene (F ST = −0.0063) were confirming the lack of population structure in Indian coastal waters. The maximum likelihood tree of cytochrome b gene showed that there were only 2 clusters and one cluster had only one representative (Hap8). The haplotypes of 16S rRNA gene were also clustered in to two groups with haplotype 1 (Hap1) as a separate group in maximum likelihood tree. The present study clearly figure out the S. serrata populations in Indian waters can be considered as a single stock during conservation and management programme.

Rock Crabs Grapsus Grapsus and Box Calappa Convexa (Crustacea: Brachyura): Potential Fishery Resources

In recent years, the demand for food resources of aquatic origen has increased considerably and this has allowed resorting to the exploration of alternative resources. Within these, some intertidal crustaceans such as the “rock crab” Grapsus grapsus and Calappa convexa “box crab” stand out due to their frequency and easy capture, which is frequently of the shrimp (Penaeus) by-catch and lobster (Panulirus) fishing. Both species of crabs, due to their sizes and abundance, represent an economic and nutritional interest for coastal fishermen in northwestern Mexico. At present, there is no fishing regulation on these resources and it is necessary and urgent to take regulatory measures of their population status of these crabs, which are constantly captured by fishermen but without biological or administrative control by te authorities responsable for their management fishing in this area.

Current Status and Conservation of Springs in Taiwan: Water Quality Assessment and Species Diversity of Aquatic Animals

Even though spring ecosystems are ecologically unique and socio-culturally important worldwide, they hardly attract research attention. The aims of this study were to evaluate the environmental status of water quality, and to inventory the species diversity of aquatic animals in 65 springs in Taiwan from 2012 to 2017, of which seven springs were unable to be sampled due the fact that they were dried or sealed up. The environmental status of 58 springs with complete water quality data was assessed by the River Pollution Index (RPI). Based on the RPI, the water quality of these 58 sampled springs was mainly non-/mildly polluted (26 springs, 44.8%) and lightly polluted (23 spring, 39.6%), and nine (15.5%) springs were moderately polluted. However, when applied to springs, the RPI may intensify the pollution rankings because dissolved oxygen is an assessing factor, and hypoxia may naturally be observed in the springs. To avoid this concern, we suggest choosing the concentration of coliform instead of dissolved oxygen content in the RPI when it is applied to springs. During the 6 years of the study period, we collected 48 fish species in 44 springs, 24 gastropoda and bivalve species in 46 springs, 16 shrimp species in 34 springs, and 14 crab species in 18 springs. Within the species collected, 31 fish, 20 gastropoda and bivalves, 12 shrimps, and 14 crabs are native species of Taiwan. They totaled 27.2 to 35% of the known aquatic native species of the island. Thus, springs in Taiwan may be considered to be a conservation hotspot of aquatic animals. Other than native species, exotic aquatic animals also represent threats, as seventeen fishes (35.4%), four gastropoda and bivalves (16.6%), and two shrimps (12.5%) were found in the springs of Taiwan. The springs in Taiwan show diverse and vital ecosystem services, such as delivering social, cultural, and economic value, conserving native and endangered freshwater animals, developing new academic theories, and supplying habitat refugees from climate change. Unfortunately, springs in Taiwan currently are also threatened by multiple anthropogenic disturbances, such as the overconsumption of groundwater by land development and urbanization, deterioration of water quality by agricultural, domestic, and industrial pollution, and inappropriate tourism and management tactics. To restore and sustain the springs in Taiwan, effective strategies and practical measures are urgently required to minimize human-caused threats and revitalize social awareness of springs.

A new species of potamid crab, Isolapotamon seowi (Brachyura, Potamoidea) from Kokol Hill in western Sabah, Malaysia, Borneo

Abstract A new species of freshwater crab of the genus Isolapotamon Bott, 1968 (Potamidae) is described from western Sabah in Malaysian Borneo. Isolapotamon seowi new species, is the sixth species of Isolapotamon known from Sabah, and differs from its closest congener, I. buntyae Ng, Low & Clark, 2022, from eastern Borneo, in possessing a relatively lower carapace, a more rugose dorsal carapace surface, the postorbital cristae being sharper and subparallel with the frontal margin, relatively shorter fourth ambulatory legs, and the terminal segment of the male first gonopod is gently curved with the subdistal process slightly longer than the distal projection and angled at 90° to the longitudinal axis.

Identification and Characterization of 5-HT Receptor 1 from Scylla paramamosain: The Essential Roles of 5-HT and Its Receptor Gene during Aggressive Behavior in Crab Species.

Biogenic amines (BAs) play an important role in the aggressive behavior of crustaceans. In mammals and birds, 5-HT and its receptor genes (5-HTRs) are characterized as essential regulators involved in neural signaling pathways during aggressive behavior. However, only one 5-HTR transcript has been reported in crabs. In this study, the full-length cDNA of the 5-HTR1 gene, named Sp5-HTR1, was first isolated from the muscle of the mud crab Scylla paramamosain using the reverse-transcription polymerase chain reaction (RT-PCR) and rapid-amplification of cDNA ends (RACE) methods. The transcript encoded a peptide of 587 amino acid residues with a molecular mass of 63.36 kDa. Western blot results indicate that the 5-HTR1 protein was expressed at the highest level in the thoracic ganglion. Furthermore, the results of quantitative real-time PCR show that the expression levels of Sp5-HTR1 in the ganglion at 0.5, 1, 2, and 4 h after 5-HT injection were significantly upregulated compared with the control group (p < 0.05). Meanwhile, the behavioral changes in 5-HT-injected crabs were analyzed with EthoVision. After 0.5 h of injection, the speed and movement distance of the crab, the duration of aggressive behavior, and the intensity of aggressiveness in the low-5-HT-concentration injection group were significantly higher than those in the saline-injection and control groups (p < 0.05). In this study, we found that the Sp5-HTR1 gene plays a role in the regulation of aggressive behavior by BAs, including 5-HT in the mud crab. The results provide reference data for the analysis of the genetic mechanism of aggressive behaviors in crabs.

Vichai cyanapelou gen. et sp. nov. (Crustacea: Deckeniidae: Hydrothelphusinae), a new genus and new species of freshwater crab from northern Madagascar

ABSTRACT A new genus and new species of freshwater crab, Vichai cyanapelou gen. et sp. nov., is described from the forested Sava Region of northern Madagascar based on morphology and previously obtained molecular data. The new genus superficially resembles several other deckeniid genera from Madagascar. A combination of characters in the carapace, mandible, cheliped, thoracic sternum, third maxilliped and male first gonopod, however, distinguish it from confamilials. Previous phylogenetic analysis using the cytochrome oxidase subunit I (COI) gene also supports the new monotypic genus and new species and shows that it forms a distinct clade separate from the 12 other Malagasy genera. Vichai cyanalepou sp. nov. is endemic to Madagascar and is here compared to other species and genera of freshwater crabs occurring in that country. http://www.zoobank.org/urn:lsid:zoobank.org:pub:46218584-43FE-4C05-9537-FFC81EACCFDB http://www.zoobank.org/urn:lsid:zoobank.org:act:B5985969-B677-47E4BE59-37C1308B7A66

The Complete Mitochondrial Genome of the Hermit Crab Diogenes edwardsii (Anomura: Diogenidae) and Phylogenetic Relationships within Infraorder Anomura.

A complete mitochondrial genome (mitogenome) can provide important information for gene rearrangement, molecular evolution and phylogenetic analysis. Currently, only a few mitogenomes of hermit crabs (superfamily Paguridae) in the infraorder Anomura have been reported. This study reports the first complete mitogenome of the hermit crab Diogenes edwardsii assembled using high-throughput sequencing. The mitogenome of Diogenes edwardsii is 19,858 bp in length and comprises 13 protein-coding genes, 2 ribosomal RNA genes, and 22 transfer RNA genes. There are 28 and six genes observed on the heavy and light strands, respectively. The genome composition was highly A + T biased (72.16%), and exhibited a negative AT-skew (-0.110) and positive GC-skew (0.233). Phylogenetic analyses based on the nucleotide dataset of 16 Anomura species indicated that D. edwardsii was closest related to Clibanarius infraspinatus in the same family, Diogenidae. Positive selection analysis showed that two residues located in cox1 and cox2 were identified as positively selected sites with high BEB value (>95%), indicating that these two genes are under positive selection pressure. This is the first complete mitogenome of the genus Diogenes, and this finding helps us to represent a new genomic resource for hermit crab species and provide data for further evolutionary status of Diogenidae in Anomura.

A new freshwater crab species of the genus Vela Bahir &amp;amp; Yeo, 2007 (Decapoda: Brachyura: Gecarcinucidae) from the Western Ghats of Karnataka, India

Vela bandhavya sp. nov., a new species of gecarcinucid crab is described from the Central Western Ghats, Uttara Kannada district, Karnataka state, India. The new species can be immediately distinguished from three other species of Vela Bahir & Yeo, 2007, mainly by its short male sternopleonal cavity and a relatively shorter distal article of the male first gonopod. The diagnosis of Vela is revised to accommodate the new species, and an illustrated identification key is provided for all four species. An anomalous adult male crab, with a pair of pleopods on the pleonal somite 5 in addition to the male gonopods, is also reported.

The exploitation of crabs by Last Interglacial Iberian Neanderthals: The evidence from Gruta da Figueira Brava (Portugal)

Hominin consumption of small prey has been much discussed over the past decades. Such resources are often considered to be unproductive in the Middle Paleolithic due to their limited meat yield and, hence, low energy return. However, ethnographic studies suggest that small prey—including shellfish—are a reliable, predictable and by no means marginal resource, and there is increasing evidence for their inclusion in hominin diets during the Middle Paleolithic and even earlier. Gruta da Figueira Brava features a MIS 5c-5b Neanderthal occupation that left behind substantial, human-accumulated terrestrial and marine faunal remains, capped by reworked levels that contain some naturally accumulated, recent Holocene material, namely the remains of small crab species and echinoderms. The brown crabCancer pagurus(Linnaeus, 1758) predominates in the intact Middle Paleolithic deposit, and reconstruction of its carapace width, based on regression from claw size, shows a preference for relatively large individuals. The detailed analysis of theCancer pagurusremains reveals that complete animals were brought to the site, where they were roasted on coals and then cracked open to access the flesh.