Land Crab Research Articles

Is Marine Dispersion of the Lethargic Crab Disease Possible? Assessing the Tolerance of Exophiala cancerae to a Broad Combination of Salinities, Temperatures, and Exposure Times.

Since 1997, an emergent fungal disease named lethargic crab disease (LCD) has decimated stocks of the edible mangrove land crab Ucides cordatus (Linnaeus, 1763) (Brachyura: Ocypodidae) along the Brazilian coast, threatening the mangrove ecosystem and causing socioeconomic impacts. Evidence from a variety of sources suggests that the black yeast Exophiala cancerae (Herpotrichiellaceae, Chaetothyriales) has been responsible for such epizootic events. Based on the spatiotemporal patterns of the LCD outbreaks, the well-established surface ocean currents, and the range of ecological traits of Exophiala spp., a marine dispersal hypothesis may be proposed. Using in vitro experiments, we tested the survival and growth of E. cancerae CBS 120420 in a broad combination of salinities, temperatures, and exposure times. While variation in salinity did not significantly affect the growth of colony-forming units (CFUs) (P>0.05), long exposure times visibly influenced an increase in CFUs growth (P<0.05). However, higher temperature (30°C) caused a reduction of about 1.2-fold in CFUs growth (P<0.05). This result suggests that sea surface temperatures either above or below the optimum growth range of E. cancerae could play a key role in the apparent north-south limits in the geographical distribution of LCD outbreaks. In light of our results, we conclude that a fundamental step toward the understanding of LCD epidemiological dynamics should comprise a systematic screening of E. cancerae in estuarine and coastal waters.

The secondary invasion of giant African land snail has little impact on litter or seedling dynamics in rainforest

AbstractIn the absence of empirical evidence, invasive species are often assumed to have negative impacts because of their conspicuously high abundance. The giant African land snail Achatina (Lissachatina) fulica is one such invader where its impact in natural ecosystems remains completely untested. On Christmas Island (Indian Ocean), A. fulica has become established across large tracts of rainforest following the impacts of invasive yellow crazy ant (Anoplolepis gracilipes) in mutualism with non‐native scale insects. Yellow crazy ants facilitate the secondary invasion of A. fulica by extirpating native red land crabs (Gecarcoidea natalis) that are normally effective predators of A. fulica. We used a multifaceted approach to investigate some potential impacts of abundant A. fulica in invaded rainforest. Over the course of a wet season, diel activity transects showed that A. fulica consumed detrital material almost exclusively. However, stable isotope analysis did not confidently identify A. fulica as a predominantly detritivorous species. We found no statistically significant treatment effects of A. fulica exclusion on standing leaf litter and seedling recruitment processes during a 6‐month manipulative field study. However, litter cover and biomass did remain slightly higher where A. fulica were excluded, albeit with overlapping confidence intervals with control plots. Our study constitutes the first empirical test for impact of A. fulica in a natural ecosystem and suggests that for Christmas Island rainforest, this species is not a damaging invader. Other studies will need to assess the impacts of A. fulica in other natural areas before these findings could be considered broadly applicable.

The Land Crabs of Costa Rica

The land crabs of Costa Rica, members of the families Gecarcinidae and Coenobitidae, are described and keys are presented for their identification. A review of the recent literature is presented and also a brief discussion of the habits and life history of these land crabs. Species accounts include information on common name, range, collecting sites, size, habitat and color.

Stable isotope analysis as an early monitoring tool for community‐scale effects of rat eradication

AbstractInvasive rats have colonized most of the islands of the world, resulting in strong negative impacts on native biodiversity and on ecosystem functions. As prolific omnivores, invasive rats can cause local extirpation of a wide range of native species, with cascading consequences that can reshape communities and ecosystems. Eradication of rats on islands is now becoming a widespread approach to restore ecosystems, and many native island species show strong numerical responses to rat eradication. However, the effect of rat eradication on other consumers can extend beyond direct numerical effects, to changes in behavior, dietary composition, and other ecological parameters. These behavioral and trophic effects may have strong cascading impacts on the ecology of restored ecosystems, but they have rarely been examined. In this study, we explore how rat eradication has affected the trophic ecology of native land crab communities. Using stable isotope analysis of rats and crabs, we demonstrate that the diet or trophic position of most crabs changed subsequent to rat eradication. Combined with the numerical recovery of two carnivorous land crab species (Geograpsus spp.), this led to a dramatic widening of the crab trophic niche following rat eradication. Given the established importance of land crabs in structuring island communities, particularly plants, this suggests an unappreciated mechanism by which rat eradication may alter island ecology. This study also demonstrates the potential for stable isotope analysis as a complementary monitoring tool to traditional techniques, with the potential to provide more nuanced assessments of the community‐ and ecosystem‐wide effects of restoration.

Fossil hermit and land crabs (Decapoda: Anomura, Brachyura) from the Quaternary of Antigua and Bermuda

Fossil hermit and land crabs (Decapoda: Anomura, Brachyura) from the Quaternary of Antigua and Bermuda

Eradicating invasive rodents from wet and dry tropical islands in Mexico

AbstractEradications of invasive rodents from tropical islands have a lower success rate compared to temperate islands. In the tropics the wide range of physical and biological conditions results in a wide variety of island biomes, with unique challenges and windows of opportunity for rodent eradications. We describe and compare research and operational details of six successful eradications of invasive miceMus musculusand ship ratsRattus rattuscarried out during 2011–2015. The work was conducted on six islands in two distinct tropical archipelagos in Mexico (one dry in the Gulf of Mexico; one wet in the Caribbean), and included the first eradication of rats from a mangrove-dominated island &gt; 500 ha. Invasive rodent populations varied among species and islands, even neighbouring islands; overall density was higher on wet islands. Physical and biological features, including the presence of land crabs, determined eradication timing and rates of bait broadcast (higher on wet islands). An interval of 6–10 days between the two bait applications per island was sufficient to eradicate actively breeding mouse and rat populations. Impacts on non-target species were negligible, including those on wild and captive iguanas. Eradication success was rapidly confirmed based on ground monitoring and statistical modelling. Rodent eradications on larger tropical islands should be achievable with directed research to inform planning and implementation.

Polymorphism in the chelae of mature males of the land crabs Johngarthia lagostoma and Epigrapsus spp.

The growth of the chelae of mature males was examined in three gecarcinid land crabs — Johngarthia lagostoma on Ascension Island, Epigrapsus notatus on Taiwan, and E. politus on Moorea. Chelar dimorphism was found in each species, with a mixture of homochelous and heterochelous males. In J. lagostoma there was progressive polymorphism, with the heterochelous condition appearing only in a proportion of the larger mature males. The situation in Epigrapsus was less clear. The proportion of heterochelous males increased in the larger mature size classes, but progressive polymorphism is yet to be confirmed.

The systematics of land crabs of the genus Gecarcoidea and recognition of a pseudocryptic species, G. humei, from the eastern Indian Ocean (Crustacea : Decapoda : Gecarcinidae)

The gecarcinid genus Gecarcoidea H. Milne Edwards, 1837 is currently represented by two species from the Indo-West Pacific – the widely distributed purple land crab, G. lalandii H. Milne Edwards, 1837, and the red crab endemic to Christmas Island, G. natalis (Pocock, 1889). One species, G. humei (Wood-Mason, 1874), described from the Nicobar Islands, has had a confused taxonomic history, but was treated as a junior synonym of G. lalandii by Türkay (1974) in his revision of the family. In this study, using molecular as well as morphological characters, we show that G. humei is a valid species. Gecarcoidea lalandii and G. humei have distinct non-overlapping distributions throughout much of their range, with G. lalandii occurring in most of South-east Asia and the West Pacific, while G. humei is known only from the eastern Indian Ocean. On Christmas Island, in the eastern Indian Ocean, however, all three species are present. As a result, Christmas Island is the only locality where all extant species of Gecarcoidea are found. The three species can also be separated by differences in live colours and patterns, as well as proportions of the carapace, male abdomen, ambulatory legs and third maxillipeds, and details of the orbits and male first gonopods.

On the extant type material of Cardisoma hirtipes Dana, 1851, and Cardisoma obesum Dana, 1851 (Crustacea: Brachyura: Gecarcinidae)

Abstract Two boxes in the U.S. National Museum of Natural History, Smithsonian Institution, were found to contain the dried type material of the land crabs Cardisoma hirtipes Dana, 1851, and Cardisoma obesum Dana, 1851 (Gecarcinidae). The types of the common Pacific land crab, C. hirtipes, were believed to have been lost and a neotype had been designated in earlier revisions. Cardisoma obesum Dana, 1851 is currently regarded as a junior subjective synonym of Cardisoma carnifex (Herbst, 1796).

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

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

Estimation of density and abundance of the blue land crab, Cardisoma guanhumi Latreille, 1828, in the Imburana peninsula, northern Brazil

The blue land crab (Cardisoma guanhumi Latreille, 1828) supports extensive small-scale artisanal fisheries in the tropical western Atlantic, including Brazil. Land surveys were conducted on a peninsula in a northeastern Brazilian estuary in 2014-2015 in order to evaluate density and abundance. The study area (26 700 m2) was dividied into three subareas with a total of 30 sampling points. In all, 529 burrows were registered of which 71.7% were open (indicating activity), 22.1% were closed (indicating moulting) and 6.2% were empty (fishermen catch). Burrow diameter ranged from 12 to 174 mm (mean: 62.05 ± 3.01 mm; 95% confidence interval). The highly significant correlation between mean burrow diameter and mean carapace length (n = 7; R2 = 0.8968, ) shows that one is a good proxy for the other. The estimated total population size in the study area was 10 362 individuals, with a mean density of 0.39 individuals/m2 (stock of 7347 kg).

A tale of two antennules: the performance of crab odour-capture organs in air and water.

Odour capture is an important part of olfaction, where dissolved chemical cues (odours) are brought into contact with chemosensory structures. Antennule flicking by marine crabs is an example of discrete odour capture (sniffing) where an array of chemosensory hairs is waved through the water to create a flow-no flow pattern based on a narrow range of speeds, diameters of and spacings between hairs. Changing the speed of movement and spacing of hairs at this scale to manipulate flow represents a complicated fluid dynamics problem. In this study, we use numerical simulation of the advection and diffusion of a chemical gradient to reveal how morphological differences of the hair arrays affect odour capture. Specifically, we simulate odour capture by a marine crab (Callinectes sapidus) and a terrestrial crab (Coenobita rugosus) in both air and water to compare performance. We find that the antennule morphologies of each species are adaptions to capturing odours in their native habitats. Sniffing is an important part of odour capture for marine crabs in water where the diffusivity of odorant molecules is low and flow through the array is necessary. On the other hand, flow within the hair array diminishes odour-capture performance in air where diffusivities are high. This study highlights some of the adaptations necessary to transition from water to air.

Changes to the natural history of islands in the Chagos Atolls, Central Indian Ocean, during human settlement (1780-1969), and prospects for restoration

The Chagos Archipelago (British Indian Ocean Territory, or BIOT) has 55 islands totalling approximately 5,000 ha spread over approximately 50,000 km 2 of the central Indian Ocean. From the first human settlements, which occurred in the late 1700s, and for the following century, all of the larger islands were converted into coconut plantations. During this period the disturbance to and elimination of the native flora and fauna in Chagos atolls was especially profound because these islands were used solely for the production of coconut and its products. Regarding vegetation, many times more species were introduced than were native, and several introduced species subsequently became invasive. The bird colonies, turtles and the land crabs were hugely reduced due to human consumption, land disturbance and the introduction of rats and other inappropriate and often free-ranging animals, such as pigs. The condition of the reefs, however, remains excellent, such that the area was declared a no-take marine reserve in 2010. For some years, BIOT was the world’s largest marine no-take conservation area. This status was achieved mainly because of its reefs; the islands are still heavily dominated by increasingly derelict, rat-infested coconut plantations and lack birds on most previously planted islands. However, on the smallest islands, many no larger than a few ha in size, there are both native plant communities and huge numbers of breeding seabirds. These relatively undisturbed fragments are acting as the core of current conservation efforts to restore some of the larger islands to their pre-plantation condition. This paper documents, as far as is possible from the relatively sparse archival documents, the course of events and extent of the terrestrial changes that took place in this archipelago before modern concepts of conservation emerged and remarks on the present, planned and funded restoration efforts that can be based on such knowledge.

A new species of long-legged terrestrial Terrapotamon Ng, 1986(Crustacea: Brachyura: Potamidae) from limestone formations in Satun, southern Thailand.

A new species of terrestrial potamid crab, Terrapotamon longitarsus, is described from limestone hills in Satun Province in southern Thailand. It is easily distinguished from other Terrapotamon species by its conspicuously long ambulatory legs (all congeners have proportionately short legs), relatively smooth dorsal surface of carapace, transversely narrow male thoracic sternites 1-4, and a characteristically structured male first gonopod.

Localization and expression of molt-inhibiting hormone and nitric oxide synthase in the central nervous system of the green shore crab, Carcinus maenas, and the blackback land crab, Gecarcinus lateralis

In decapod crustaceans, molting is controlled by the pulsatile release of molt-inhibiting hormone (MIH) from neurosecretory cells in the X-organ/sinus gland (XO/SG) complex in the eyestalk ganglia (ESG). A drop in MIH release triggers molting by activating the molting gland or Y-organ (YO). Post-transcriptional mechanisms ultimately control MIH levels in the hemolymph. Neurotransmitter-mediated electrical activity controls Ca2+-dependent vesicular release of MIH from the SG axon terminals, which may be modulated by nitric oxide (NO). In green shore crab, Carcinus maenas, nitric oxide synthase (NOS) protein and NO are present in the SG. Moreover, C. maenas are refractory to eyestalk ablation (ESA), suggesting other regions of the nervous system secrete sufficient amounts of MIH to prevent molting. By contrast, ESA induces molting in the blackback land crab, Gecarcinus lateralis. Double-label immunofluorescence microscopy and quantitative polymerase chain reaction were used to localize and quantify MIH and NOS proteins and transcripts, respectively, in the ESG, brain, and thoracic ganglion (TG) of C. maenas and G. lateralis. In ESG, MIH- and NOS-immunopositive cells were closely associated in the SG of both species; confocal microscopy showed that NOS was localized in cells adjacent to MIH-positive axon terminals. In brain, MIH-positive cells were located in a small number of cells in the olfactory lobe; no NOS immunofluorescence was detected. In TG, MIH and NOS were localized in cell clusters between the segmental nerves. In G. lateralis, Gl-MIH and Gl-crustacean hyperglycemic hormone (CHH) mRNA levels were ~105-fold higher in ESG than in brain or TG of intermolt animals, indicating that the ESG is the primary source of these neuropeptides. Gl-NOS and Gl-elongation factor (EF2) mRNA levels were also higher in the ESG. Molt stage had little or no effect on CHH, NOS, NOS-interacting protein (NOS-IP), membrane Guanylyl Cyclase-II (GC-II), and NO-independent GC-III expression in the ESG of both species. By contrast, MIH and NO receptor GC-I beta subunit (GC-Iβ) transcripts were increased during premolt and postmolt stages in G. lateralis, but not in C. maenas. MIH immunopositive cells in the brain and TG may be a secondary source of MIH; the release of MIH from these sources may contribute to the difference between the two species in response to ESA. The MIH-immunopositive cells in the TG may be the source of an MIH-like factor that mediates molt inhibition by limb bud autotomy. The association of MIH- and NOS-labeled cells in the ESG and TG suggests that NO may modulate MIH release. A model is proposed in which NO-dependent activation of GC-I inhibits Ca2+-dependent fusion of MIH vesicles with the nerve terminal membrane; the resulting decrease in MIH activates the YO and the animal enters premolt.

Caracterização Topográfica do Habitat do Cardisoma guanhumi Latreille, 1828 (Decapoda, Gecarcinidae) na Apa Costa dos Corais (Pernambuco e Alagoas, Brasil)

In the period from July to September 2012, a survey was made of the number of burrows of blue land crab ( Cardisoma guanhumi ), both in twelve profiles distributed in areas of mangrove, positioned perpendicularly to the wetlands of the Una's River (Pernambuco) and Camaragibe's River (Alagoas), aiming to acquire information on the distribution of holes in different types of topographies. The depth of burrows and the salinity and temperature of the water at the bottom of the burrows was registered. In Pernambuco and Alagoas, the profiles covered steep areas (with a gradient of 4.5°) and shallow areas (with a gradient of 0.02°). The maximum distance between existing burrows in the profiles, ranged from 58m and 359.5m, compared to a benchmark level (RN). The burrows depths ranged from 0.45m to 1.90m, with an depth average of 0.99m (DP = 0,29). The maximum depth of the burrows can be justified by the fact that there is less availability of water in northeastern soils.It is recommended, studied the mangroves, the establishment of an exclusion zone to preserve the habitat of Cardisoma guanhumi , a distance of at least 200m above the high tide mark. Keywords: blue land crab; mangrove; burrows.

Some ecological aspects of the gecarcinid land crab, &lt;i&gt;Cardisoma armatum&lt;/i&gt; Herklots, 1851 (Crustacea, Brachyura, Gecarcinidae) from the estuarine region of the Comoe River, Côte d’Ivoire

Cardisoma armatum Herklots, 1851 is a land crab endemic to tropical coastal ecosystems and represents an important fishery resource. C. armatum was collected using traps at the eastern region of the Ebrie lagoon and the estuarine region of the Comoe River in 2009 during the high rainy season extending from mid-May to mid-July and in low dry season from mid-July to September. Some biometric parameters are measured to determine some aspects of population structure and condition of this edible crab. Sexual dimorphism was confirmed with the major chelae of male crabs reaching larger sizes than those of females. The sex ratio that varied with the sampling periods was associated with migrations occurring during the breeding season. Positive, negative, and positive allometric growth patterns were observed for the carapace length-total weight relationship, respectively, in males, females, and the population as a whole. For the carapace width/total weight relationship, negative allometric growth was observed, respectively, in males, females, and the whole population. Our data show an evidence of a serious problem of recruitment in the population of this crab related to degradation of the habitats and heavy harvesting pressures, highlighting the necessity of developing and implanting management and protection strategies of this crustacean. © 2016 International Formulae Group. All rights reserved. Keywords: Cardisoma armatum , Population structure, Condition index, Ebrie lagoon, Comoe River, Cote d’Ivoire

Habitat augmentation drives secondary invasion: an experimental approach to determine the mechanism of invasion success.

The entry of secondary invaders into, or their expansion within, native communities is contingent on the changes wrought by other (primary) invaders. When primary invaders have altered more than one property of the recipient community, standard descriptive and modeling approaches only provide a best guess of the mechanism permitting the secondary invasion. In rainforest on Christmas Island, we conducted a manipulative field experiment to determine the mechanism of invasion success for a community of land snails dominated by non-native species. The invasion of rainforest by the yellow crazy ant (Anoplolepis gracilipes) has facilitated these land snails, either by creating enemy-free space and/or increased habitat and resources (in the form of leaf litter) through the removal of the native omnivorous-detritivorous red land crab (Gecarcoidea natalis). We manipulated predator densities (high and low) and leaf litter (high and low) in replicated blocks of four treatment combinations at two sites. Over the course of one wet season (fivemonths), we found that plots with high leaf litter biomass contained significantly more snails than those with low biomass, regardless of whether those plots had high or low predation pressure, at both the site where land crabs have always been abundant, and at the site where they have been absent for many years prior to the experiment. Each site was dominated by small snail species (<2mm length), and through handling size and predation experiments we demonstrated that red crabs tend not to handle and eat snails of that size. These results suggest that secondary invasion by this community of non-native land snails is facilitated most strongly by habitat and resource augmentation, an indirect consequence of red land crab removal, and that the creation of enemy-free space is not important. By using a full-factorial experimental approach, we have confidently determined-rather than inferred-the mechanism by which primary invaders indirectly facilitate a community of secondary invaders.

La mosca del cangrejo terrestre Cardisoma crassum Smith (Crustacea: Gecarcinidae) en la Isla del Coco, Costa Rica

Commensal, phoretic relalionship and other types of associations of Diptera and land crabs are known from various parts of the world. A commensal relationship between an unidentified species of Sphaeroceridae (Diptera) and Cardisoma crassum Smith (Crustacea: Gecarcinidae) from Cocos Island, Costa Rica, is reported for the first time. The pattern of infection is closely similar to that of Drosophila and Lissocephala (Diptera: Drosophilidae) found associated with other gecarcinids elsewhere. The Sphaeroceridae are apparently obligatorily exploiting an exclusive niche in the restricted environment, suggesting a genetical mechanism of adaptation for this particular group of Diptera, possibly derived and favored by geographical isolation.

Terrestrial arthropods from the Late Pleistocene of Jamaica - systematics, palaeoecology and taphonomy: supplement

The Red Hills Road Cave, Jamaica, is the most important site for terrestrial arthropods in the post-Miocene of the Greater Antilles. Its fauna includes millipedes, isopods, crabs and insects, in addition to land snails and vertebrates. Arthropods are preserved in three dimensions and delicate structures such as limbs can be recognized. This unusual preservation was favoured by acidic groundwater rich in dissolved calcium carbonate; periods of high rainfall during which the bottle-shaped cave was filled with water; and any arthropod washed in would have drowned. The absence of spiders, centipedes and most insects is due to the absence of carbonate in their exoskeletons. Millipedes and isopods possess a potential for preservation by carbonate mineralization that does not occur in other groups; they secrete calcium carbonate in the exoskeleton which hardens the cuticle and is water permeable, bringing about mineral replacement of the original structures. Within the cave, fossil millipede taxa include Rhinocricus sp. or spp., Chondrotropis sp., Caraibodesmus verrucosus (Pocock) and Cyclodesmus sp. cf. C. porcellanus Pocock. The isopod fauna includes Pseudarmadillo sp., Venezillo boonae Van Name, and Philoscia spp. 1 and 2. Crab claws belong to Sesarma sp. cf. S. cookei Hartnoll. Millipedes and isopods are particularly complete, representing drowned individuals fossilized soon after death; land crabs occur as fingers and rare chelae, suggesting that they may be exuviae. Only the most robust parts of insects have been discovered, but are particularly rare, consisting of three taxa of fly puparia and one possible beetle elytra. Copyright © 2012 John Wiley & Sons, Ltd.