Land Crab Research Articles

In silico analysis of crustacean hyperglycemic hormone family G protein-coupled receptor candidates.

Ecdysteroid molting hormone synthesis is directed by a pair of molting glands or Y-organs (YOs), and this synthesis is inhibited by molt-inhibiting hormone (MIH). MIH is a member of the crustacean hyperglycemic hormone (CHH) neuropeptide superfamily, which includes CHH and insect ion transport peptide (ITP). It is hypothesized that the MIH receptor is a Class A (Rhodopsin-like) G protein-coupled receptor (GPCR). The YO of the blackback land crab, Gecarcinus lateralis, expresses 49 Class A GPCRs, three of which (Gl-CHHR-A9, -A10, and -A12) were provisionally assigned as CHH-like receptors. CrusTome, a transcriptome database assembled from 189 crustaceans and 12 ecdysozoan outgroups, was used to deorphanize candidate MIH/CHH GPCRs, relying on sequence homology to three functionally characterized ITP receptors (BNGR-A2, BNGR-A24, and BNGR-A34) in the silk moth, Bombyx mori. Phylogenetic analysis and multiple sequence alignments across major taxonomic groups revealed extensive expansion and diversification of crustacean A2, A24, and A34 receptors, designated CHH Family Receptor Candidates (CFRCs). The A2 clade was divided into three subclades; A24 clade was divided into five subclades; and A34 was divided into six subclades. The subclades were distinguished by conserved motifs in extracellular loop (ECL) 2 and ECL3 in the ligand-binding region. Eleven of the 14 subclades occurred in decapod crustaceans. In G. lateralis, seven CFRC sequences, designated Gl-CFRC-A2α1, -A24α, -A24β1, -A24β2, -A34α2, -A34β1, and -A34β2, were identified; the three A34 sequences corresponded to Gl-GPCR-A12, -A9, and A10, respectively. ECL2 in all the CFRC sequences had a two-stranded β-sheet structure similar to human Class A GPCRs, whereas the ECL2 of decapod CFRC-A34β1/β2 had an additional two-stranded β-sheet. We hypothesize that this second β-sheet on ECL2 plays a role in MIH/CHH binding and activation, which will be investigated further with functional assays.

Holocene Crab Consumption at Watinglo, Papua New Guinea

Malacostraca are commonly found in coastal archaeological sites in the Indo-Pacific; both swimming and terrestrial crabs. This archaeological evidence as well as ethnographic studies indicate that they formed an important component of the human diet in the past as they still do in many regions today.  However, they often go unidentified and largely unanalysed in archaeological research due to the highly fragmentary state of the remains and the associated difficulties posed for identification and quantification. Here we discuss these issues and provide an example of crab remains recovered from a coastal archaeological site in Papua New Guinea, Watinglo shelter, with an occupation record spanning from the Terminal Pleistocene to historic times. We also briefly compare these finding to crab remains from archaeological sites of similar antiquity in Indonesia and the Philippines.

Histopatological Impact of Malathion on the Reproductive Organs of Freshwater Crabs Barytelhusa Cunicularis (Westwood, 1836)

Crabs are particularly useful in aquatic environment and play a very important role in the ecosystem processes and good indicator for polluted condition. The terrestrial crab plays a significant modal in the study of population and also beneficial for human activities. The present study deals with the histochemical changes of organophosphate, malathion in the freshwater crab Barytelphusa cunicularis. Live specimens of Barytelphusa cunicularis were collected from local wet areas of Marodasector, Bhilai, (C.G). The crabs were sexed on the basis of the shape of the abdomen. Average weight of crabs varies from (45-50 gms), the carapace length and carapace width varies from 3.20-4.50mm and 4.25-5.80mm respectively. The crabs were acclimatized in the laboratory condition, and kept in two groups the control group set free from Malathion and the experimental group was exposed to malathion for LC50 at different concentration 0.45ppm, 0.30ppm, 0.26ppm and 0.25ppm for 24hrs, 48hrs, 72hrs and 96hrs respectively. The sections of 5µm were taken for the histopathological examination of testis and ovary; affected due to the impact of Malathion, the testicular follicular cells interstitials cells and nutritive cells were decreased and distracted number of sperm cells it exhibited irregular arrangement of nucleus, in the ovary epithelial layer destruction, degeneration of oocytes, Shrinkage in ooplasm, vacuolization and reduction in cytoplasmic material. The result suggests that rapid utilization to meet the energy demands under the impact of malathion.

Species-specific gill’s microbiome of eight crab species with different breathing adaptations

Transitions to physically different environments, such as the water-to-land transition, proved to be the main drivers of relevant evolutionary events. Brachyuran crabs evolved remarkable morphological, behavioral, and physiological adaptations to terrestrial life. Terrestrial species evolved new respiratory structures devoted to replace or support the gills, a multifunctional organ devoted to gas exchanges, ion-regulation and nitrogen excretion. It was hypothesized that microorganisms associated with respiratory apparatus could have facilitated the processes of osmoregulation, respiration, and elimination of metabolites along this evolutionary transition. To test if crab species with different breathing adaptations may host similar microbial communities on their gills, we performed a comparative targeted-metagenomic analysis, selecting two marine and six terrestrial crabs belonging to different families and characterised by different breathing adaptations. We analysed anterior and posterior gills separately according to their different and specific roles. Regardless of their terrestrial or marine adaptations, microbial assemblages were strongly species-specific indicating a non-random association between the host and its microbiome. Significant differences were found in only two terrestrial species when considering posterior vs. anterior gills, without any association with species-specific respiratory adaptations. Our results suggest that all the selected species are strongly adapted to the ecological niche and specific micro-habitat they colonise.

Using Public Sightings to Document the Widespread Distribution of the Non-Endemic Blue Land Crab, Cardisoma guanhumi, in South Carolina

Using Public Sightings to Document the Widespread Distribution of the Non-Endemic Blue Land Crab, Cardisoma guanhumi, in South Carolina

Description of a Highly Modified Endemic Ground Beetle (Coleoptera, Carabidae) from the Oceanic Island of Malpelo, Colombia

The oceanic island of Malpelo, 380 km west of the Colombian mainland, stands out from other islands of the Tropical Eastern Pacific by its harsh environment and depauperate flora and fauna, thus imposing strong selective pressure on the small number of invertebrates that inhabit it. The endemic taxon described here, Dyscolus (Cacothrix) malpelensis, n. subgen., n. sp. (Carabidae, Platynini), is a remarkable example of adaptation to this unique ecosystem. The modifications of its body shape, including a tight coaptation of elytra and pronotum, might be a response to strong environmental constraints, from predation by lizards and land crabs to the absence of deep soil that forces the beetle to seek shelter in caves and rock crevices.

The diversity and distribution of Gecarcinidae MacLeay, 1838 (Crustacea: Decapoda: Brachyura), a potential land crab as a valuable food resource, in Indonesia

Gecarcinidae is one of the land crabs that is commonly found in intertidal and coastal areas comprises of 28 species worldwide. On some regions, this crab has been known as one of food resources. However, Indonesians have no interest yet in consuming this potentially high-value species. The present study aims to reveal the diversity and distribution of Gecarcinidae in Indonesia and discuss its potencies. Specimens of Gecarcinidae deposited in Museum Zoologicum Bogoriense (MZB) were used for observation and their morphological differences were recorded. Their recorded localities were used to define the hypothetical distribution. Their economic potential assessments were based on some literatures. In total, there are five species recorded in Indonesia, i.e., Cardisoma carnifex, Gecarcoidea humei, Gecarcoidea lalandii Tuerkayana hirtipes, and Tuerkayana magnum. The widest-distributed species are Cardisoma carnifex and Tuerkayana hirtipes. Among these species, the two largest species are Cardisoma carnifex and Tuerkayana magnum. In Pacific regions, Gecarcoidea is harvested as one of food resources. Therefore, these five species have high potency to support food sustainability and revealing the potencies and chance for captivity could serve as a catalyst to elevate community welfare, especially in coastal areas. Conservation on the natural habitat is necessary to maintain the sustainable utilization.

Intraspecific color diversity and camouflage associated with ontogeny in an insular land crab

Intraspecific color diversity and camouflage associated with ontogeny in an insular land crab

The Pathogenic Yeast Metschnikowia bicuspidata var. bicuspidata in the Aquacultured Ecosystem and Its Biocontrol.

M. bicuspidata var. bicuspidata is a pathogenic yeast which can affect aquacultured and marine-cultured animals such as brine shrimp, ridgetail white prawn, chinook salmon, giant freshwater prawn, the Chinese mitten crab, marine crab, the mud crab, the mangrove land crab, the Chinese grass shrimp, sea urchins, sea urchins, Daphnia dentifera and even snails, causing a milky disease, and it has caused big economic losses in aquacultural and marine-cultural industries in the past. However, the detailed mechanisms and the reasons for the milky disease in the diseased aquatic animals are still completely unknown. So far, only some antimycotics, killer toxins and Massoia lactone haven been found to be able to actively control and kill its growth. The ecofriendly, green and renewable killer toxins and Massoia lactone have high potential for application in controlling the milky disease.

“Capture with a camera!” A non-contact method for obtaining the body size data from ovigerous female land crabs during breeding migration

Abstract Body size is a crucial metric that is often obtained during the breeding migration of female land crabs. Most commonly, these measurements are obtained by hand but hand-measuring them carries risks for both crabs and researchers. In this study, we developed a novel “photo-image approach” to measure the maximum carapace width of Cardisoma carnifex (Herbst, 1796) in the field, and compared the results with hand measurements. We found a significant relationship in the maximum carapace width measured between the two approaches (Linear regression, , ). The difference (0.54 ± 0.18 mm) and relative error (0.61 ± 0.19%) in the maximum carapace width measured between the two approaches were minimal. We suggest that the photo-image approach is feasible for determining crab size in the field. The approach holds promise for its application in citizen science projects, facilitating advancements in crab research.

Variation and taphonomic implications of composition in modern and fossil malacostracan cuticles (Decapoda: Malacostraca)

Abstract The crustacean fossil record is dominated by mineralized forms. These fossils, in turn, are mainly decapod chelae or parts of chelae. Studies of the composition of modern crustacean cuticles have likewise been dominated by decapods. We summarize major element chemical analyses (Ca, Mg, Na, P) using SEM-EDS of modern crustacean exoskeletons from Bermuda, Georgia (USA), and Lake Tanganyika (Burundi). Although most specimens were brachyuran and anomuran crabs, material also included examples of stomatopods, isopods, caridean shrimps, and achelatans. Transects were made of sections of the carapace, palm of the propodus, and tips of either the dactyl or propodus. Multiple transects were made of the Bermudan land crab Gecarcinus lateralis. Additional studies were made of brachyuran fossil crabs from Texas and South Dakota and of brachyuran crabs having undergone ten months of burial in marine sediments. Overall, the tips of the chela were the thickest and most heavily mineralized regions and had the lowest phosphorus content. In nearly all cases, they also had the lowest ratios of Mg to Ca. One notable exception was Gecarcinus, where the denticles had elevated Mg:Ca values. Anomura and Brachyura had markedly different composition from Stomatopoda and possibly Isopoda, suggestive of independent evolutionary origins of biomineralization within the Crustacea. There were also significant differences in composition between brachyuran crabs from Georgia and Bermuda, perhaps due to differences in water temperature. The fossil crustaceans had much more phosphate in their cuticles, likely as a result of diagenetic processes. Composition should be a first order control on the fossil record of crustaceans. Future studies need to expand the taxonomic and geographic ranges of material examined, determine whether there are environmental controls on composition, and explore the relevant diagenetic processes.

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.

Effects of molting on the expression of ecdysteroid biosynthesis genes in the Y-organ of the blackback land crab, Gecarcinus lateralis

A pair of Y-organs (YOs) synthesize ecdysteroids that initiate and coordinate molting processes in decapod crustaceans. The YO converts cholesterol to secreted products through a biosynthetic pathway involving a Rieske oxygenase encoded by Neverland (Nvd) and cytochrome P450 monooxygenases encoded by Halloween genes Spook (Spo; Cyp307a1), Phantom (Phm; Cyp306a1), Disembodied (Dib; Cyp302a1), and Shadow (Sad; Cyp315a1). NAD kinase (NADK) and 5-aminolevulinic acid synthase (ALAS) support ecdysteroid synthesis in insects. A 20-hydroxylase, encoded by Shed in decapods and Shade in insects, converts ecdysone to the active hormone 20-hydroxyecdysone (20E). 20E is inactivated by cytochrome P450 26-hydroxylase (Cyp18a1). Contigs encoding these eight proteins were extracted from a Gecarcinus lateralis YO transcriptome and their expression was quantified by quantitative polymerase chain reaction. mRNA levels of Gl-Spo and Gl-Phm were four orders of magnitude higher in YO than those in nine other tissues, while mRNA levels of Gl-NADK and Gl-ALAS were similar in all ten tissues. In G. lateralis induced to molt by multiple leg autotomy, YO mRNA levels of Gl-Nvd, Gl-Spo, Gl-Phm, Gl-NADK, and Gl-ALAS were highest in intermolt and premolt stages and lower in postmolt. Gl-Dib mRNA level was not affected by molt stage. mRNA level of Gl-Sad, which converts 2-deoxyecdysone to ecdysone, was higher in mid- and late premolt stages, when YO ecdysteroidogenic capacity is greatest. Gl-Cyp18a1 mRNA level was highest in intermolt, decreased in premolt stages, and was lowest in postmolt. In animals induced to molt by eyestalk ablation, YO mRNA levels of all eight genes were not correlated with increased hemolymph 20E titers. These results suggest that YO ecdysteroidogenic genes are differentially regulated at transcriptional and translational levels.

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.

Habitat use, non-breeding groupings and chromatic pattern in Johngarthia lagostoma (H. Milne Edwards, 1837) (Decapoda, Gecarcinidae) in Trindade Island, South Atlantic Ocean

The land crab Johngarthia lagostoma is endemic to Trindade Island, Atol das Rocas, Fernando de Noronha and Ascension Islands. The natural history of the species in non-breeding periods is little known. Therefore, here we reported the formation of non-breeding groups and evaluated the chromatic populational pattern of J. lagostoma in Trindade Island. Records were obtained between April and June 2015. The groups were characterized according to their location, terrain elevation, environmental characteristics and specimens’ behavior. The chromatic pattern was defined by the classification of individuals between yellow and purple, and the proportion of each color was compared between populational units (previously defined based on genetic differences). Non-breeding groups were recorded in four locations in Trindade Island, at altitudes < 40 m, and all of them were in locations with food resources and sediment suitable for the construction of shelters. Isolated individuals or the absence of the species were observed in the most inhospitable places, indicating that the maintenance of the species depends on portions of suitable habitat amid the currently arid matrix. Yellow individuals (96.4%) were predominant on Trindade Island and the chromatic pattern differed from the other populations. Color patterns seem to follow genetic differences between populations, and the founder effect may account for current patterns. From the data obtained, we emphasize that the maintenance of the species may depend on food, sediment suitable for shelters construction, humidity and shade. Due to the significant population decline in other regions, the need to define guidelines for the conservation of the species on Trindade Island is highlighted. In this context, the regeneration of insular vegetation and prohibiting the known anthropic consumption of individuals may represent important strategies for the maintenance of the species.

Terrestrial food web of the Malpelo Fauna and Flora Sanctuary, Colombia: An analysis from a topological approach

Malpelo Island is the largest marine protected area (MPA) in the Colombian Pacific; however, the lack of information regarding its ecological dynamics suggests that management and conservation strategies are developed from an individual approach (species or groups of species) and not from an ecosystem one. This study analyzes the terrestrial food web of Malpelo Island, Colombia, based on topological analysis (e.g., centrality). The food web was constructed from 27 nodes representing the main trophogroups, which consist of species or functional groups. Malpelo Island had a food web of four steps with a maximum separation among all trophogroups and trophic pathways, with two steps in average length. Furthermore, the food web was divided into three food web compartments, with a recurrence of connectivity patterns dominated by apparent and exploitative competition, followed by tri-trophic chains and omnivory. Five key trophogroups control the energy flow throughout the food web (detritus, the land crab Johngarthia malpilensis, the lizard Anolis agassizi, the Malpelo dotted galliwasp Diploglossus millepunctatus, and the Nazca booby Sula granti). The high importance of detritus suggests that bottom-up processes act as a control and regulation mechanism of trophic flows. The low number of food web compartments and a high recurrence of specific connectivity patterns in the Malpelo Island terrestrial ecosystem evidence different ecological processes centered on five trophogroups, allowing stability against disturbances. In addition, the simulation of trophogroup removal (randomly or directed) suggests that food web can be vulnerable to structural alterations in their properties, which may have consequences on the resilience of this ecosystem. This study contributes to the knowledge of the trophic dynamics of Malpelo Island, providing a potential tool for management and conservation measures from an ecosystemic approach.

Heavy metal health risk assessment in Cardisoma armatum Herklots, 1951 land crab tissues around Kribi mangrove areas, Cameroon

Bioaccumulation of heavy metals in mangrove crabs has been reported and most of them are toxic to animals and potential human carcinogens. Given that the land crab Cardisoma armatum Herklots, 1951 is more consumed by surrounding populations, this study aimed to quantify the levels of metals in its tissues and to assess the human health risks. Soft tissues were isolated in adult crabs and frozen then; samples were dried, crushed and handled following the standard procedures. Human health risks were evaluated using some indices. Heavy metal levels in each tissue were shown in decreasing order: Fe > Zn > Al > Cu > Cd > Pb. Cadmium, lead and copper metals were in upper levels in the hepatopancreas (0.35, 0.19 and 7.88 mg/kg) whereas iron, aluminium and zinc were higher in muscles (129.30, 15.96 and 82.83 mg/kg). Most EDI values were apparently below the PTDI and CRLim values signifying that the consumption of C. armatum remains safe for consumers although, a limit in intake frequency might be required for children. For all metals, THQ and HI values were below the standard value 1 indicating no health risks in consumers due to the intake of single or several metals. Also, the carcinogenic risks for Cd and Pb metals are considered to be negligible because they are lower than 10−6. Overall, regarding the results, consumption of C. armatum seems harmless for human health in the study area.

Occurrence and Health Risk Assessment of Heavy Metals in the Blue Land Crab (Cardisoma guanhumi) from a Tropical Mangrove Swamp.

Coastal ecosystems in the Caribbean are vulnerable to pollution from land-based activities with possible impacts to human health. Ten heavy metals in the blue land crab, Cardisoma guanhumi, harvested from the Caroni Swamp, Trinidad, were investigated in the wet and dry seasons. Metal concentrations (µg g-1 dry weight) in crab tissue were: As (0.15-6.46), Ba (0.69-19.64), Cd (< 0.001-3.36), Cr (0.63-3.64), Cu (26.64-120.31), Hg (0.09-1.83), Ni (1.21-9.33), Se (0.19-1.55), V (0.16-0.69) and Zn (121.06-494.3). There were seasonal differences in the concentration of some heavy metals and, Cu and Zn exceeded the local maximum permissible levels for fish and shellfish at several sites in either one or both seasons. Health risk assessment based on estimated daily intake, target hazard quotient and hazard index revealed that Cardisoma guanhumi harvested from the Caroni Swamp, does not pose a health risk to consumers.

Tuerkayana latens, a New Species of Land Crab from French Polynesia, with a Discussion on the Phylogeny of the Genus (Crustacea: Decapoda: Brachyura: Gecarcinidae).

The taxonomy of the gecarcinid land crab Tuerkayana rotundum (Quoy & Gaimard, 1824) is revised. The taxon, the type species of the genus, occurs from the western Indian Ocean to the western Pacific, and varies substantially in colour and various morphological features, but the male first gonopod structure is constant and the extensive genetic data from mitochondrial 16S rDNA, cytochrome c oxidase subunit 1 and control region markers confirms the recognition of one wide-ranging species. Specimens from Tuamotu in French Polynesia and Pitcairn Island, however, differ in having a smoother and slightly more swollen carapace, and significantly, the male first gonopod structure is distinctly different. The genetic data also supports their differentiation. As such, this material is here recognised as a new species, Tuerkayana latens n. sp.

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.