Crab Species Research Articles

An updated ecological assessment of floral and faunal communities of mangrove habitats in Tolo Harbour and Channel, Hong Kong

Mangrove forests are coastal habitats of ecological and socio-economic importance, and those in Hong Kong have been found to support high species diversity. Located in northeastern Hong Kong, the mangroves in the Tolo Harbour and Channel (the Tolo area), like many mangrove communities in Hong Kong, have suffered from considerable threat due to rapid coastal development. To provide up-to-date ecological information on the species composition and diversity of major mangrove stands in the Tolo area and advise conservation priorities, surveys were conducted to investigate spatial and temporal variations in species composition of epibenthic and arboreal organisms and to quantify tree diversity in mangrove stands covering inner to outer Tolo areas. A total of 127 species/taxa were recorded in the Tolo area of which 51 were gastropods and 34 were crustaceans. Species richness was higher in the inner Tolo area associated with larger mangrove stands than the outer Tolo area. Mangrove tree communities varied spatially whereas epibenthic and arboreal communities varied both spatially and seasonally. Outer Tolo mangroves had more crab species than inner Tolo area, whereas mangrove stands in Plover Cove and inner Tolo Channel areas were richer in species and had taller mangrove trees as well as presence of endemic species. Priority should be given to conserve mangrove stands in Plover Cove and inner Tolo Channel areas in order to conserve the ecological value of the Tolo area. The present dataset could serve as a baseline for future environmental monitoring and management programmes on the mangrove habitats in the Tolo area.

New Records of Three Species of Swimming Crabs (Decapoda, Brachyura, Portunidae) from the Maldives

New Records of Three Species of Swimming Crabs (Decapoda, Brachyura, Portunidae) from the Maldives

Candidate Species for Florida Aquaculture: American Horseshoe Crab Limulus polyphemus

The American horseshoe crab, Limulus polyphemus, is a member of the phylum Arthropoda, subphylum Chelicerata, and class Merostomata. Although there are four horseshoe crab species worldwide, the American horseshoe crab is primarily found in the Atlantic Ocean along the East Coast of North America. The species ranges from Maine to Mexico, but is absent between Texas in the United States and Tabasco in Mexico. They mainly inhabit estuarine areas; however, juveniles and adults can venture into the shallow oceanic environments. Embryo development occurs in the intertidal zone of sandy beaches. Sandy or muddy bottom habitats are necessary for burrowing and benthic feeding. This publication will cover their natural history, aquaculture techniques, common diseases, and their uses and markets.

Insights into the Habitat Choice for the Culture of Himalayapotamon emphysetum under Laboratory Conditions

The main aim of the present study was to scrutinize the substrate and microhabitat preferred by the Himalayapotamon emphysetum under laboratory conditions. In the first experiment, different substrates: gravel, stones, and cobbles were placed in the round plastic containers, and in the second experiment: grass, aquatic plants, and wood fragments were used as microhabitats for analyzing the preference of the crab species. Minimum mortality was observed when the crabs were provided with the substrate of stones and wood fragments as the microhabitat. The results of the present study provide a better understanding of the breeding and culture of commercially important crab species of Jammu and Kashmir Union Territory and can be used as a reference for determining the culture conditions for Himalaypotamon emphysetum that will boost the economy of this region. The studies related to the preference of habitat and substrate of any species is essential for aquaculture and breeding programs.

Diversity of Fishery Organisms and Their Contribution to The Community Sustainability of Kilifi Creek, Kenya

Fishery organisms are a source of food and income in local societies surrounding any water body. Investigations were carried out to study the diversity and distribution of fishery organisms of the Kilifi estuarine creek and their contribution to community sustainability. Sampling took place at Sea horse, Fumbini, Konjora, and Rare on the northern arm and at Nkoma, Mazioni, Fumbini, and Kombeni on the southern arm of the creek. All fishery organisms obtained were identified, counted and length dimensions taken. The 1444 prawns obtained were Fenneropenaeus indicus and Penaeus monodon while the 207 were four crab species Portunus armatus, Portunus sanguinolentus, Scylla serrata, and Thalamita crenata. F. indicus was the most abundant of the prawn species whereas P. armatus and S. serrata were caught at all study sites in smaller class sizes. 7,258 finfishes identified were 85 species belonging to 14 orders, 46 families. Biodiversity indices analysed showed that Margalef’s species richness index was highest (8.293) at Sea horse and lowest (3.874) at Rare. Pielou’s evenness was highest (0.7286) at Nkoma and lowest (0.5319) at Rare. Simpson’s diversity index was highest at Nkoma (0.8917) and lowest at Rare (0.6672). Bray-Curtis similarity grouped all fishes into three ecosystems, open sea waters, the mudflats, and river channels. The most abundant finfish species were Leiognathus equula (20.17 %) followed by Mugil cephalus (17.64%), Gerres filamentosus (10.25%), and Pomadasys multimaculatum (7.37%). Most abundant finfish species and crustaceans were in small class sizes hence for local consumption by communities around the creek

Morphological Description of Ocean-Collected Portunus sp. First Crab (Crustacea: Brachyura: Portunidae) from the Obhur Creek, Red Sea, Saudi Arabia

Twenty-one specimens of Portunus sp. first crab were obtained from plankton samples collected from the Obhur Creek, Central Red Sea, Saudi Arabia. These specimens have been morphologically described herein. The setal patterns of the first crabs of the present specimens were compared with those of the first crabs of P. sanguinolentus. Presence of two to three rows of setae on the coxa of maxillule and coxa and basial of the first maxilliped are found in both the species of Portunus first crabs compared herein. These features seem to be taxonomically significant as these features are found in one of the other genera of Portunidae – Thalamita.

A new species of the genus Eutrichopagurus Komai, 2015 (Crustacea: Decapoda: Anomura: Paguridae) from a submarine cave in the Ryukyu Islands, southwestern Japan

A new hermit crab species of the family Paguridae is described on the basis of two male specimens from Hedo Dome, a submarine cave located on the north coast of Okinawa Island, Ryukyu Islands, southwestern Japan. The assignment of the new species to the genus Eutrichopagurus Komai, 2015 is based on the structure of the gills and right male sexual tube, the article 3 of the antennular peduncle with a prominent tuft of setae on the dorsodistal margin, and the posterior lateral margins of the telson each bearing a prominent tuft of setae. Among two known congeners, Eutrichopagurus crassoculus n. sp. may be closer to the type species of the genus, E. shirakawai Komai, 2015, in having greatly reduced corneas, basally bearing sparse setae, and no small corneous spines or spiniform setae on the dorsal surface of the meri of the ambulatory legs, but is distinguishable by the morphology of the ocular peduncles, ocular acicle, antennular peduncle, and chelipeds.

On two species of Aniptumnus Ng, 2002 (Crustacea: Brachyura: Pilumnidae) from India, with a description of a new species from the coast of Kerala

The taxonomy of two species of Indian pilumnid crabs is treated herein. Heteropanope neolaevis Deb, 1985, originally described from northeastern India, is retained in the genus Aniptumnus Ng, 2002 as a valid species and removed from synonymy with Aniptumnus quadridentatus (De Man, 1895). A new species, Aniptumnus bijoyi, is described from southwestern India, based on distinguishing features in the carapace, thoracic sternum, pereopods and gonopods. With these developments, five species of Aniptumnus are now recognized.

Identification and Morphology of the Two Horseshoe Crab Species, Tachypleus tridentatus (Leah, 1819) and Carcinoscorpius rotundicauda (Latreille, 1802) (Merostomata: Limulidae) from Honda Bay, Palawan, Philippines

There were reports of the existence of horseshoe crabs in Palawan, Philippines, but there is a need to identify and confirm these species. A total of 128 adult horseshoe crabs were collected from Honda Bay, Palawan, Philippines. These were identified as Tachypleus tridentatus (68 males, 40 females) and Carcinoscorpius rotundicauda (2 males, 18 females). Morphology, morphometric measurements, and ratios of male and female of each species were described. Morphological characteristics in differentiating a male from a female crab involve examination of the appearance of the genitalia. Morphological characteristics in identifying the species include the presence or absence of notches in the frontal margin, arching in the frontal view, appearance of the chelae of the 2nd and 3rd prosomal appendages, number of lateral spines and the immovable spines in the opisthosoma, the presence of spinnerets on the surface of the telson, and shape of the telson and its cavity in cross-section. This study confirmed the identification of the two species found in Palawan, Philippines, and the morphological characteristics of the male and female of each species. In addition, a comparison was made of the size of the horseshoe crab species in Palawan with those found in other locations in the Asia-Pacific region.

A new semiterrestrial crab from limestone hills in Vietnam (Crustacea: Brachyura: Potamidae: Tiwaripotamon).

A new species of semiterrestrial crab of the potamid genus Tiwaripotamon Bott, 1970, is described from limestone hills in northern Vietnam. Tiwaripotamon bellum n. sp. is one of the largest known species in the genus, and its external morphology is most similar to T. vietnamicum (Đăng & Hồ, 2002), described from northern Vietnam. Tiwaripotamon bellum n. sp., however, can easily be separated by its much darker colour in life, possession of a distinct epibranchial tooth on the carapace, the proportionately shorter ambulatory meri, and the gently curved terminal segment of the male first gonopod, with a subtruncate tip and dorsal lobe on the proximal part of the structure.

Transcriptomic Signature of Horseshoe Crab Carcinoscorpius rotundicauda Hemocytes' Response to Lipopolysaccharides.

Carcinoscorpius rotundicauda (C. rotundicauda) is one of the four species of horseshoe crabs (HSCs). The HSC hemocytes store defense molecules that are released upon encountering invading pathogens. The HSCs rely on this innate immunity to continue its existence as a living fossil for more than 480 million years. To gain insight into the innate mechanisms involved, transcriptomic analysis was performed on isolated C. rotundicauda hemocytes challenged with lipopolysaccharides (LPS), the main components of the outer cell membrane of gram-negative bacteria. RNA-sequencing with Illumina HiSeq platform resulted in 232,628,086 and 245,448,176 raw reads corresponding to 190,326,253 and 201,180,020 high-quality mappable reads from control and LPS-stimulated hemocytes, respectively. Following LPS-stimulation, 79 genes were significantly upregulated and 265 genes were downregulated. The differentially expressed genes (DEGs) were related to multiple immune functional categories and pathways such as those of the cytoskeleton, Toll and Imd, apoptosis, MAP kinase (MAPK), inositol phosphate metabolism, phagosome, leucocyte endothelial migration, and gram-negative bacterial infection, among others. This study provides important information about the mechanisms of response to LPS, which is relevant for the understanding the HSCs' immune response.

A new species of pea crab of the genus Indopinnixa Manning & Morton, 1987 (Decapoda, Brachyura, Pinnotheridae) from Flores in eastern Indonesia, with a key to the genus

Abstract A new species of pinnotherid crab, Indopinnixa latimerus n. sp. is described on the basis of a female specimen from the island of Flores in Indonesia. This new species resembles I. oryza Naruse & Maenosono, 2012 in having a subovate carapace, without any protuberance on the lateral margin, and a distally expanded merus of the fourth ambulatory leg, but differs in the shape of the frontal margin, and the density of the setation of the carapace and chelipeds. A key to the nine known species of Indopinnixa is provided.

A new species of hermit crab of the genus Pagurus Fabricius, 1775 (Crustacea: Anomura: Paguridae) from north-western Africa

One male and two female specimens of an undescribed species of the heterogeneous hermit crab genus Pagurus Fabricius, 1775, were found during the study of the collections of the Oceanographic Institute of Cádiz, containing specimens from African and European coasts collected during the scientific cruises carried out between in years 2008-2013. The new species is named Pagurus pectinidactylus n. sp., in reference to the presence of a well-developed toothless pectinate masticatory border in the dactylus of the left cheliped, composed by a row of tightly placed bristles forming a brush-like structure. The new species is compared to morphologically similar congeners, especially those that are genetically closest. Molecular phylogenetic analyses support the morphological delimitation, with P. pectinidactylus n. sp. forming a separate clade, more closely related to a group of South African species belonging to the Pagurus anachoretus group.

Gurumon gurumayum, a new genus and new species of freshwater crab (Decapoda: Brachyura: Potamidae) from Arunachal Pradesh, northeastern India

A new genus and new species of potamid crab, Gurumon gurumayum gen. et sp. nov., are described from the Arunachal Pradesh State of northeastern India. Gurumon gen. nov. has affinities with Abormon Mitra, Pati & Ng, 2021, Pararanguna Dai & Chen, 1985, and some species of Potamiscus Alcock, 1909, but the new genus can easily be differentiated from them mainly by its low external orbital angle, the relatively stouter exopod of the third maxilliped, and the relatively broader male pleonal somite 6. Their male first gonopods are also different from each other. Counting Gurumon gurumayum gen. et sp. nov., India is currently known for ten genera and 24 species of potamiscine freshwater crabs, and Arunachal Pradesh for eight genera and 11 species of these crabs. The current nomenclatural problems with Potamiscus are also discussed.

Double Valorization for a Discard-α-Chitin and Calcium Lactate Production from the Crab Polybius henslowii Using a Deep Eutectic Solvent Approach.

Polybius henslowii, an abundant yet unexploited species of swimming crab, was investigated as a potential source of α-chitin and calcium lactate using deep eutectic solvents (DES) as extracting solvents. Choline chloride-malonic acid (CCMA) and choline chloride-lactic acid (CCLA) were used to obtain high purity α-chitin from ball-milled P. henslowii exoskeleton in 2 h at 120 °C, with yields of 12.05 ± 2.54% and 12.8 ± 1.54%, respectively. The physical and chemical characteristics of the obtained chitins were assessed using CHN elemental analysis, attenuated total reflectance-Fourier transform infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy. Furthermore, the CCLA solvent was reusable three times with little effect on the extract purity, and calcium lactate was produced at the end of the recycling cycles. The ensuing calcium lactate was also characterized in terms of chemical and physical properties. The obtained chitin is a promising raw material for downstream processing and the double valorization pathway with the obtention of calcium salts may increase the viability of a DES-based approach for the processing of mineralized substrates.

Redescription of Pseudograpsus intermedius Chhapgar, 1955 (Decapoda, Brachyura, Varunidae) from India

The identity of Pseudograpsus intermedius Chhapgar, 1955 (Varunidae), a crab species found in mangrove habitats of India is clarified. The re-examination of the holotype male and examination of fresh specimens collected from Goa State, India, revealed that P. intermedius shows significant morphological differences from the generic characters of Pseudograpsus. As such, a new genus Chhapgarus n. gen. is established for the species.

A multidisciplinary integrated approach using Pachygrapsus marmoratus to assess the impact of port activities on mediterranean marine protected areas

The establishment of marine protected areas is considered the main global strategy to halt the loss of marine biodiversity. Since most of marine areas are open systems, this form of habitat protection cannot prevent their contamination due to human activities performed outside of their borders. Innovative approaches to assess the health status of protected marine habitats are therefore needed. Here we developed a multidisciplinary approach that combines ecological characteristics, bioaccumulation of inorganic and organic pollutants, cell damage (micronuclei frequency, nuclear alterations and LPO) and enzymatic (AChE, CAT, IDH, LDH, GST and CAT) markers focused on an intertidal brachyuran crab, Pachygrapsus marmoratus, to assess the impacts of contaminant exposure on Mediterranean coastal habitats. As study sites we selected two protected areas and two sites within industrial ports of the Ligurian Sea. Our results showed that the selected crab species is an excellent bioindicator. Individuals collected in sites with the highest levels of heavy metal pollution showed the highest signals of stress responses at both cellular and enzymatic levels, coupled with a high incidence of the parasite Sacculina carcini, a signal of impairment of their standard development and reproduction cycle. We could also prove that one of the selected marine protected areas showed the same intensity of impact as its adjacent port site. Our multidisciplinary approach proved to be a valuable tool to assess the environmental quality and health of protected and disturbed Mediterranean coastal environments and to inform efficient management and protection schemes for such habitats.

A new potential risk: The impacts of Klebsiella pneumoniae infection on the histopathology, transcriptome and metagenome of Chinese mitten crab (Eriocheir sinensis)

Klebsiella pneumoniae is a common conditional pathogen found in natural soil water sources and vegetation and can infect invertebrates, vertebrates, and plants. In this study, we isolated K. pneumoniae from the hepatopancreas of the Chinese mitten crab (Eriocheir sinensis) for the first time and then we analysed its effects of on the histopathological changes, the transcriptome of the hepatopancreas, and the gut microbiota of this crab species. The findings of this study showed that K. pneumoniae infection has led to significant structural changes in the hepatopancreas, such as the production of vacuolated tissue structures, disorganized cell arrangement, and lysis of some hepatopancreatic cells. Also, the infection caused activation of the antioxidant-related enzymes such as SOD and CAT by inducing oxidative stress. The transcriptome of the hepatopancreas identified 10,940 differentially expressed genes (DEGs) in the susceptible (SG) groups and control (CG) groups, and 8495 DEGs in the SG groups and anti-infective (AI) groups. The KEGG pathway revealed upregulated DEGs caused by K. pneumoniae infection that involved in the immune response and apoptotic functional pathways, and also downregulated DEGs involved in the digestive absorption, metabolic, and biosynthetic signaling pathways. Meanwhile, metagenics sequencing revealed that at the phylum, class, order, family, and genus levels, K. pneumoniae infection altered the composition of the gut microbiota of E. sinensis, through increasing the abundance of Prolixibacteraceae, Enterobacterales, and Roseimarinus and decreasing the abundance of Alphaproteobacteria. The flora structure has also been changed between the SG and AI groups, with the abundance of Firmicutes, Erysipelotrichales, and Erysipelotrichaceae that were significantly decreased in the SG groups than in the AI groups. But, the abundance of Acinetobacter was considerably higher than in the AI group. In summary, K. pneumoniae infection induced oxidative stress in E. sinensis, triggered changes in immune-related gene expression, and caused structural changes in the gut microbiota. This study provides data to support the analysis of bacterial infection probes in several crustacean species.

Cryptic and widespread: a recipe for taxonomic misidentification in a freshwater crab species (Decapoda: Potamonautidae:Potamonautes sidneyi) as evident from species delimitation methods

AbstractWe examined the systematics of a ubiquitously distributed southern African freshwater crab, Potamonautes sidneyi s.l. species complex. Specimens were subjected to DNA sequence analyses of two mitochondrial loci (16S rRNA + COI). We applied three species delimitations methods (ASAP, bGMYC and bPTP) to test their utility in delineating species boundaries in Potamonautes and three additional Afrotropical genera (Liberonautes, Nesonautes and Seychellum). The combined mtDNA dataset retrieved five clades. Clade 1 comprised of P. barbarai, clade 2 comprised of specimens from the interior of the Great Karoo Basin, sister to P. sidneyi s.s. in clade 3. Clade 4 was confined to Eswatini and the Mpumalanga Province of South Africa, and sister to clade 5 that comprised P. danielsi. The three species delimitation methods either over- or underestimated the number of species. Phylogenetically, specimens from the Great Karoo Basin (clade 2) were equidistant to P. sidneyi s.s. and P. perlatus, while the Eswatini and Mpumalanga specimens (clade 4) were sister to P. danielsi. Clades 2 and 4 are herein described as P. karooensis sp. nov. and P. valles sp. nov., respectively.

Metabolomic analysis of secondary metabolites from Caribbean crab gills using comprehensive two-dimensional gas chromatography - time-of-flight mass spectrometry—New inputs for a better understanding of symbiotic associations in crustaceans

Secondary metabolites are bioactive compounds produced by living organisms that can be indicative of symbiotic relationships in nature. Prior studies have demonstrated putative symbiotic interactions between decapod crabs and epibiotic bacteria in their environment. This study presents a sample preparation protocol for metabolomics analysis of lyophilized crab gill samples from four brachyuran crab species inhabiting different regions of Guadeloupe, Lesser Antilles. Sample extracts were prepared using a two-step methoximation-trimethylsilylation derivatization protocol and analyzed by comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry (GC×GC-TOFMS). Three main secondary metabolites identified in the crab gills and discussed herein include cycloserine, trigonelline, and amphetamine. Cycloserine is a bacterial-produced metabolite with antibiotic properties, and along with the antimicrobial activity of trigonelline, these compounds may influence the microbial community of the crabs and/or protect them from bacterial infection in the frame of the symbiotic relationships. Amphetamine is a psychostimulant that has been previously detected in crab muscles, and has been found in crab gills in this study. Cycloserine was present in the gills of Ucides cordatus and Percnon gibbesi, trigonelline was present in all crabs except Ucides cordatus, and amphetamine was detected in all crab gill samples. Further research into these secondary metabolites is facilitated with the sample preparation protocol and can elucidate the various symbiotic interactions of crabs and their microbiome; potentially for other crustaceans as well.