Freshwater Crab Research Articles

Adaptive evolution characteristics of mitochondrial genomes in genus Aparapotamon (Brachyura, Potamidae) of freshwater crabs

BackgroundAparapotamon, a freshwater crab genus endemic to China, includes 13 species. The distribution of Aparapotamon spans the first and second tiers of China's terrain ladder, showing great altitudinal differences. To study the molecular mechanisms of adaptive evolution in Aparapotamon, we performed evolutionary analyses, including morphological, geographical, and phylogenetic analyses and divergence time estimation. We sequenced the mitogenomes of Aparapotamon binchuanense and Aparapotamon huizeense for the first time and resequenced three other mitogenomes of Aparapotamon grahami and Aparapotamon gracilipedum. These sequences were combined with NCBI sequences to perform comparative mitogenome analysis of all 13 Aparapotamon species, revealing mitogenome arrangement and the characteristics of protein-coding and tRNA genes.ResultsA new species classification scheme of the genus Aparapotamon has been detected and verified by different aspects, including geographical, morphological, phylogenetics and comparative mitogenome analyses. Imprints from adaptive evolution were discovered in the mitochondrial genomes of group A, including the same codon loss at position 416 of the ND6 gene and the unique arrangement pattern of the tRNA-Ile gene. Multiple tRNA genes conserved or involved in adaptive evolution were detected. Two genes associated with altitudinal adaptation, ATP8 and ND6, which experienced positive selection, were identified for the first time in freshwater crabs.ConclusionsGeological movements of the Qinghai-Tibet Plateau and Hengduan Mountains likely strongly impacted the speciation and differentiation of the four Aparapotamon groups. After some group A species dispersed from the Hengduan Mountain Range, new evolutionary characteristics emerged in their mitochondrial genomes, facilitating adaptation to the low-altitude environment of China's second terrain tier. Ultimately, group A species spread to high latitudes along the upper reaches of the Yangtze River, showing faster evolutionary rates, higher species diversity and the widest distribution.

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.

Stable isotopes of archaeological and modern semi-terrestrial crabs (Potamon potamios) provide paleoecological insights into brachyuran ecology and human resource acquisition in late Holocene Jordan

Archaeological remains of brachyurans (e.g. crabs) are often overlooked as potential paleoenvironmental and paleoclimatical proxies in contrast to other marine and terrestrial invertebrates such as mollusks and landsnails. The potential for fine-scale regional paleoclimate reconstruction based upon these organisms' behavioral ecology has yet to be examined. We present novel isotopic analyses of the remains of a semiterrestrial freshwater crab (Potamon potamios) endemic to southwest Asia recovered from the archaeological site of Khirbat al-Mudayna al-’Aliya (KMA). KMA lies on a southern tributary of the Wadi al-Mujib in the Hashemite Kingdom of Jordan, approximately 40 km east of the Dead Sea. Excavations here recovered architecture, artifacts, and ecofacts dating to a single-period occupation during the early Iron Age (∼1000 cal BCE). Oxygen and carbon isotopes from these brachyuran remains were analyzed in conjunction with a two-year isotopic and morphometric study of the modern potomonautid population near the archaeological site and at nearby wadi systems to assess whether the isotopic values of modern crab populations correlated with variables such as temperature, including isotopic study of the pools in which crabs were found. In turn, these data could be used to reconstruct paleoclimate or paleoenvironment in the archaeological population. The high correlation in oxygen isotope values between crab carapaces and the water of the pools in which they were sampled suggest that variability in isotopic values of crab specimens recovered from KMA is tracking ancient human capture of these organisms across potentially different pools. Further, intra-year variability in isotopic values in modern crab carapaces as well as the similarity of isotopic values across wadi systems with different environments suggest that P. potamios remains cannot be used as reliable paleoenvironmental indicators. The implications of this research will have significance for archaeologists and other researchers in the study of paleoenvironment and paleoecology, and bears upon human mobility, resource acquisition, and human-nonhuman animal relationships.

Potamon persicum Pretzmann,1962’nin et verimi ve kimyasal bileşimi

In this study, morphometric measurement, meat yield, moisture, pH, protein, fat, fatty acids and ash content were determined in a total of 102 (15 female and 87 male) freshwater crab (Potamon persicum Pretzmann,1962) caught from Aşağı and Yukarı Çay of Pertek, Tunceli. Meat yield in male and in female crabs were found to be as 12.75±0.38% and 10.93±0.32%, respectively. It has been observed that moisture and protein amounts were higher in female crabs than in male crabs. The amounts of fat were 0.96±0.31% in male crabs and 0.97±0.35% in female crabs. The amount of ash was 2.68±0.04% in male crabs and 2.66±0.03% in female crabs. It was determined that the content of monounsaturated fatty acids (female:male 33.56%:37.44%) in female and male crabs were higher than polyunsaturated (female:male 24.19%:21.62%) and saturated fatty acid (female:male 28.11%:32.85%) content. The highest fatty acid was found to be as omega-9, in terms of omega-3 (male crabs 8.54%, female crabs 14.85%), omega-6 (male crabs 10.04%, female crabs 5.46%) and omega-9 fatty acids (male crabs 23.65%, female crabs 19.14%) in freshwater crab (Potamon persicum Pretzmann, 1962) meat.

Identification of acid phosphatase (ShACP) from the freshwater crab Sinopotamon henanense and its expression pattern changes in response to cadmium

Acid phosphatase(ACP) is an important immune enzyme in crustacean humoral immunity. At present, the research on ACP mainly focuses on the biochemical properties of the enzyme, while few studies on gene expression. In this study, ShACP was cloned and the effect of cadmium stress on the expression and function of ShACP in the freshwater crab Sinopotamon henanense was studied. Analysis of the ShACP sequence and tissue distribution results showed that the cDNA sequence of ShACP was 1629 bp, including 48 bp 5′ untranslated region, 1209 bp open reading frame region, and 372 bp 3′ untranslated region, encoding 402 amino acids. ShACP contained multiple phosphorylation sites and mainly played a role in the hemolymph. Under low-concentration cadmium stress, the body improved immunity by enhancing the expression of ShACP, while high-concentration cadmium stress inhibited the expression of ShACP. ShACP can promote the phagocytosis of hemocytes, while cadmium stress reduced the phagocytosis of hemocytes. This study provides a theoretical basis for further research on the immune system of crabs and is of great significance for the study of crustacean immune responses under heavy metal stress.

Diversity of freshwater crabs, their importance, threats, and conservation aspects

Diversity of freshwater crabs, their importance, threats, and conservation aspects

Mitochondrial genomic characterization of two endemic Chinese freshwater crabs of the genus Sinopotamon (Brachyura: Potamidae) and implications for biogeography analysis of Potamidae.

As an endemic freshwater crab group in China, the phylogenetic relationships within Sinopotamon are still controversial because of the limited taxon samples. In this study, the complete mitogenomes of Sinopotamon chishuiense with 17,311 bp and the nearly complete mitogenomes of S.wushanense with 16,785 bp were firstly sequenced and analyzed. Compared with other reported mitogenomes of Potamidae, some novel patterns of gene rearrangement were detected in these two Sinopotamon mitogenomes, which could be illuminated by the mechanisms of tandem duplication-random loss, recombination, and translocation. Phylogenetic analyses showed the nonmonophyly of the Sinopotamon and a sister group relationship with Tenuilapotamon. These crabs from the eastern and southern of the Yangtze River basin were more closely related while other crabs form the plateau areas formed a separate clade. Divergence time indicated that the Sinopotamon and its sister group Tenuilapotamon diverged from other potamiscine freshwater crabs approximately 42.65 Mya, which belongs to the recent main uplifts period of the Tibetan Plateau in the Late Miocene. Combined with the similar evolutionary rates and relatively stable habitat altitude of these Sinopotamon species, these results implied that the ecological environment may be relatively stable during the speciation. Overall, our study yielded worthy perceptions for the evolutionary and taxonomic relationship of Sinopotamon and will help to better clarify the gene rearrangement events of the invertebrate mitogenome and lay the foundation for further phylogenetic study of Sinopotamon. Overall, our study yielded valuable insights into the evolutionary history and taxonomic relationship of Sinopotamon and these results will help to better explain the gene rearrangement events of the invertebrate mitogenome and lay the foundation for further phylogenetic study of Sinopotamon.

Is salt the solution? Interactions between trace-metal uptake and salinity in the freshwater crabPotamonautes warreniCalman, 1918 (Decapoda: Brachyura: Potamonautidae)

AbstractCrustaceans inhabiting freshwater are more vulnerable to increased loading with dissolved trace metals than those from more saline conditions for both physicochemical and physiological reasons. Potamonautes warreni (Calman, 1918) is a true freshwater crab inhabiting rivers in proximity to mining activities in South Africa. In order to assess whether the uptake of zinc (Zn2+) and cadmium (Cd2+) were associated with Na+- and Ca2+-uptake routes, individuals of P. warreni were acclimated to different Na+ or Ca2+ concentrations before measuring trace-metal uptake into the haemolymph and tissues in an intermediate freshwater. Cd2+ uptake into the haemolymph was elevated following acclimation to ‘Na+ replete’ conditions, when compared with ‘Na+ deplete’ conditions, indicating that a physiological response to the acclimation salinity had influenced Cd2+ uptake. Zn2+ uptake by the whole body was elevated in P. warreni individuals from the ‘Na+ replete’ group when compared with crabs acclimated to Na+ free water. A general change in permeability may have occurred and indeed, the apparent water permeability (water efflux) of P. warreni was increased in elevated Na+ and Ca2+ concentrations compared with that in softer water. A comparison of the osmoregulatory ability between P. warreni and the catadromous crab Eriocheir sinensisH. Milne Edwards, 1853 highlighted the greater permeability of the latter. Lower Zn2+ and Cd2+ uptake rates were measured in P. warreni in comparison to those measured in E. sinensis by other authors, indicating that the more well adapted a species is to life in freshwater, the less susceptible they will be to metal uptake. Future investigations to understand further the mechanisms influencing Zn2+ and Cd2+ uptake are required to understand the role that salinity can play in protecting a species from trace-metals released into the environment.

Breeding cycle and seasonal biochemical changes in the gonads of the North African freshwater crab Potamon algeriense (Bott, 1967) (Brachyura: Potamidae)

Breeding cycle and seasonal biochemical changes in the gonads of the North African freshwater crab Potamon algeriense (Bott, 1967) (Brachyura: Potamidae)

The identity of the freshwater crab Aiyunamon tumidum (Wood-Mason, 1871) (Brachyura, Potamidae), with description of a new species from China

Abstract The identity of the freshwater crab, Aiyunamon tumidum (Wood-Mason, 1871), is clarified after the types are re-examined. The type series is mixed and includes specimens of two species. A syntype from Ponsee in Yunnan, P.R. China, is designated the lectotype of the species; those from Hotha in Yunnan are now referred to A. daiae (Zhang & Sun, in Zhang, Pan, Hao & Sun, 2020). Specimens which have previously been referred to as “A. tumidum” from other parts of Yunnan are here identified as a new species, Aiyunamon fatum sp. nov.. Aiyunamon fatum is most easily distinguished from congeners by the structure of the male first gonopod.

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.

Antiviral activity of Turbinaria ornata against white spot syndrome virus in freshwater crab (Paratelphusa hydrodromous)

White spot disease in penaeid shrimp is caused by white spot syndrome virus and causing serious threat to shrimp farming industry. The present study was carried out to determine the antiviral activity of Turbinaria ornata against WSSV in freshwater carbs Paratelphusa hydrodromous. The crabs were injected with acetone extract of T. ornata along with WSSV and the experimental groups were observed for more than 60 days post-infection. The efficacy of the T. ornata acetone extract was confirmed by bioassay, histopathology, and in silico analysis. GC–MS analysis of T. ornata acetone extract identified 16 compounds respectively. Docking studies recommended that pregnane-3,20-dione, 17,21-[(methylborylene)bis(oxy)]-, (5. beta)- had the highest binding energy of − 7.1 kcal/mol and could be used as a potent antiviral compound. The results of the present study confirmed that acetone extract of T. ornata has significant antiviral activity against WSSV and it can be used as a possible prophylactic in shrimp culture for prevention of WSSV infection.

Population biology of the freshwater crab Dilocarcinus pagei Stimpson, 1861 (Decapoda: Trichodactylidae) in the Araguari River, south-eastern Brazil

ABSTRACT Dilocarcinus pagei is a freshwater crab that has a wide distribution in South America, occurring in the main river basins of Brazil. Our study analysed some aspects of the population biology of D. pagei in a population that occurs in the Araguari River, in south-eastern Brazil. Crabs were sampled between September 2020 and November 2021. The population structure was analysed according to the organisms’ size, sex and life stage. The frequency of demographic groups (adults and juveniles) over months was assessed using an environmental gradient analysis and a canonical correspondence analysis (CCA). A total of 392 crabs were collected, 282 males and 110 females. Male crabs were more abundant during most of the sampling period. Thus, the sex ratio in general and for most months was biased towards males. Gradient and CCA analyses showed seasonality in the occurrence of ovigerous females. This demographic group was more frequently sampled when the local rainfall increased. Our study provides relevant information about the population and reproductive biology of D. pagei, which may contribute to the understanding of the reproductive traits of freshwater crabs and also the ecological role of this species in the environments it inhabits.

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

A new freshwater crab species of the genus Vela Bahir & 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.

Occurrence and distribution characteristics of aged microplastics in the surface water, sediment, and crabs of the aquaculture pond in the Yangtze River Delta of China

The artificial breeding of freshwater crabs in China has become the main source, accounting for 45.69 % of the total output in 2020. However, microplastics widely exist in ponds due to the addition of meals, and the aging and breakage of plastic tools, and people know little about the occurrence of microplastics in the environment and the tissues of crabs during the cultivation of crabs in ponds. In this study, the abundance and characteristics of microplastics in ponds and crabs were studied finely, and the types of microplastics produced by meals and tools and the aging degree of microplastics in different media were studied in a typical aquaculture experimental base in the Yangtze Estuary of China. After we digested all the samples, there were microplastics in the water, sediment, and inedible part of crabs and crab meals, mainly in fiber shape, with a particle size of 100~300μm, and they have a certain degree of aging. The abundance of microplastics in surface water ranges from 4.4 to 10.8 items/L, and that in sediment ranges from 28.6 to 54.3 items/100 g·dry weight sediments. The average abundance of microplastics in crabs was 23.9 ± 15.9 items/individual. The content of microplastics in crabs' intestinal tissue was the highest, followed by gills and hepatopancreas. At the same time, the microplastics found in crabs were positively correlated with crab body weight and negatively correlated with hepatopancreas index. The results show that in the process of artificial breeding pond feeding, microplastics will be released from the process of meals dissolving in water, and fall off due to wear and tear during the use of tools. Microplastics found in the water, sediments and the tissues of crabs were all aged. Humans have a risk of ingesting microplastics when they eat the tissues of nonedible parts of crabs.

A new genus and three new species of freshwater crab (Crustacea: Brachyura: Potamidae) from central and northern Vietnam

A new genus and three new species of freshwater crab (Crustacea: Brachyura: Potamidae) from central and northern Vietnam

Isotopic Diet Analysis of the Japanese Water Shrew Chimarrogale platycephala to Estimate Their Feeding Habits and the Usefulness of Body Hair Samples

The water shrew Chimarrogale platycephala is an endangered species in Japan. Although immediate conservation actions are necessary, detailed information on this species is inadequate. We compared dietary trends obtained via C. platycephala digestive contents analysis with those through stable isotope analysis (δ13C, δ15N, ‰) of non-invasive body hair and invasive muscles to elucidate their diet and evaluate usefulness of the dietary stable isotope analysis. We captured 20 shrews from three streams in Aomori Prefecture from 2013 to 2016 barring snow accumulation seasons. The digestive contents analysis showed that water shrews mainly fed on aquatic insects, whereas freshwater crabs, fishes, and terrestrial insects were also observed as diets. δ13C values from the stable isotope analysis were not significantly different between muscles and body hair and indicated a primary diet of aquatic invertebrates and fishes. δ15N values were significantly lower in muscles and indicated a similar trophic position of water shrews to fishes. In the isotope mixing model, the contribution of terrestrial invertebrates was less than 0.35 except for two individuals that showed the highest terrestrial invertebrate ratio (> 0.5) and the lowest aquatic invertebrate ratio. This study also demonstrated that body hair from any part of the back was sufficiently useful for dietary stable isotope analysis.

Cloning, identification, and functional characterization of novel prophenoloxidases (ShproPO) from the freshwater crab Sinopotamon henanense in response to cadmium exposure and Aeromonas hydrophila infection

Prophenoloxidase (proPO) is essential in the prophenoloxidase-activating system (proPO-AS) which is important for defense against foreign infection in crustaceans. However, most studies have focused on expression in the presence of a single pathogenic bacterium, and very few have addressed the presence of environmental contaminants simultaneously, such as cadmium (Cd) and Aeromonas hydrophila. Our study aimed to investigate the function of proPO in the freshwater crab Sinopotamon henanense and the changes in its expression by Cd and infection of A. hydrophila. A novel proPO from the hemocytes of S. henanense (ShproPO) was found in this research, the full-length cDNA of ShproPO was 2620 bp of encoding a protein of 678 amino acids containing three typical hemocyanin domains. The ShproPO protein could be found in both the granular (GHc) and the semi-granular hemocytes (SGHc). The ShproPO mRNA was found to be abundantly expressed in hemocytes and could be influenced by A. hydrophila infection. These results indicate that ShproPO could be involved in the antibacterial process. Further research found that low concentrations of Cd could promote its expression after infection with A. hydrophila. Therefore, it was hypothesized that Cd disrupted the response of crabs to A. hydrophila infection. Subsequently, PO enzyme activity was found to be significantly reduced through in vivo RNA interference with ShproPO, and the results suggested that ShproPO is likely to be a key enzyme in the melanization response. Finally, ShproPO was found to significantly enhance the phagocytosis of A. hydrophila-infected hemocytes by in vitro recombination, confirming that ShproPO is involved in hemocyte-mediated melanization and phagocytosis. Our findings reveal completely new insight into the immunotoxicity of Cd and the immune function of ShproPO in S. henanense.

A novel type II crustin in the innate immune response of the freshwater crab (Sinopotamon henanense) against infection and its expression changes by cadmium

Antibacterial peptide (AMP), an effector of the innate immune system, is an essential component of invertebrate innate immunity. Crustin is a family of antimicrobial peptides that are widely studied in crustaceans. Here we report a novel crustin (designated Shcrustin) from the freshwater crab Sinopotamon henanense. The results revealed that the full-length cDNA of Shcrustin was 691 bp with an open reading frame (ORF) of 510 bp. Phylogenetic analysis of the Shcrustin sequence showed that it clustered with type II crustin. Shcrustin exists in different tissues, among which the highest expression level is found in the gills. After the bacterial challenge, the expression of Shcrustin increased in hemocytes or gills. However, crustin expression was suppressed in the presence of cadmium (Cd). To elucidate the biological activity of Shcrustin, we constructed a recombinant Shcrustin protein. Purified rShcrustin could bind to a variety of bacteria and inhibit the growth of different bacteria indicating that Shcrustin has inhibitory activity against gram-positive and gram-negative bacteria. In addition, the phagocytic rate of hemocytes toward bacteria decreased after the interference of Shcrustin expression by RNA interference, suggesting that Shcrustin may be involved in such a process. Therefore, we conclude that Shcrustin may be involved in the innate immunity of S. henanense by binding to bacteria and promoting hemolymph phagocytosis to clear invading pathogens. It is an important immune effector against pathogen infection. In the presence of Cd, it may alter the expression of Shcrustin and suppress its immune function.