Ghost Crab Research Articles

Synergistic effect of extreme climatic events and urbanization on population density of the ghost crab Ocypode quadrata (Fabricius, 1787)

AbstractThe combined effects of urbanization and extreme climatic events were examined on the ghost crab Ocypode quadrata, a well‐recognized ecological indicator in sandy beaches. The effect of storm waves was assessed before and after these climate events in beaches with different levels of urbanization in the coast of Brazil, Tropical Atlantic Ocean. The number of burrows was used as a metric for the population size of O. quadrata and the number of humans along the beaches as a proxy for the urbanization level. Significant differences were recorded in this species’ population density according to the human pressure. Our core modelling approach showed that the number of O. quadrata burrows was lower after storm waves in urbanized zones, compared to non‐urbanized ones. The interaction between storm waves and urbanization impacted the number of O. quadrata burrows negatively, and suggest that species’ populations are more vulnerable to the combined effects of extreme climatic events and urbanization. Extreme events are predicted to increase in frequency in the next few decades, and may modify or impair ecosystem functioning in sandy beaches by reducing populations of the O. quadrata, an important beach scavenger, which markedly contribute to the flux of energy in coastal trophic webs.

Speciation pattern of the horned ghost crab Ocypode ceratophthalmus (Pallas, 1772): an evaluation of the drivers of Indo‐Pacific marine biodiversity using a widely distributed species

Speciation pattern of the horned ghost crab <i>Ocypode ceratophthalmus</i> (Pallas, 1772): an evaluation of the drivers of Indo‐Pacific marine biodiversity using a widely distributed species

Interaction of the Atlantic ghost crab with marine debris: Evidence from an in situ experimental approach

Sandy beaches pollution by marine debris imposes arguably threats for the biodiversity, but interaction of beach bioindicators (e.g., ghost crabs) with debris has been rarely assessed. We aimed to test whether the Atlantic ghost crab Ocypode quadrata (Fabricius, 1787) misidentifies marine debris as food sources. Cigarette butts, straws, popsicle sticks, paper napkins and styrofoams were mixed into solutions with odour of natural and industrialized food. The debris were placed around burrows on beaches with distinct human pressures (low, medium and high-impact). The species interacted with marine debris more frequently in situations of lower human impact, lower prey abundance and larger burrow diameter. These results indicate that in areas with low prey availability and larger individuals, interactions between ghost crabs and debris left by beach visitors and/or transported by winds and currents to low-impact beaches are more likely to occur, mainly near to urbanized areas.

Food preferences of two sandy beach scavengers with different foraging strategies

Beaches are interesting ecosystems on which to test foraging ecology because the resident fauna mostly depend on unpredictably supplied allochthonous food resources. This study tests the food selection of two beach scavengers with different foraging strategies. Ghost crabs (Ocypode ryderi) patrol along the shore in search of food; it was predicted that, if given equal choices, they would select the most calorie-rich food. In contrast, swash-riding plough snails (Bullia spp.) need to make immediate decisions whether to emerge from the sand to feed on a beach-cast food item before it is washed away. It was predicted that they would emerge in response to all food equally because there is no guarantee of a better meal in their immediate future. These predictions were tested in two different in situ experiments that simulated natural foraging conditions for each scavenger. Ghost crabs consumed fish (highest calorific value) significantly more often than other foods. Similarly, significantly more snails responded to fish (higher calorific value) than jellyfish (lower calorific value); a result that was consistent with snail size, but was not affected by food-cue concentration. Beach scavengers are well adapted to the challenges of the ecosystem, and although food is supplied unpredictably, they still select for high-quality food, supporting optimal foraging theory. It is hypothesized that the patchy distribution of resident macrofauna on sandy shores may (partly) reflect their foraging ecology, sensu the ideal free distribution theory.

KARAKTERISTIK HABITAT TEMPAT BERTELUR PENYU SISIK (Eretmochelys imbricata ) DI TAMAN WISATA ALAM TANJUNG KELUANG KECAMATAN KUMAI KALIMANTAN TENGAH

This research aimed to discover the characteristics of hawksbill turtle egg-laying place (Eretmochelys imbricata) in the Tanjung Keluang Nature Park of Kumai District Central Kalimantan. The data which is collected to describe the characteristics of the habitat covers the length of the beach, its width, its slope, the distance of the nest with the vegetation, the air humidity, the air temperature, the nest temperature, the moisture content of sand substrate, the texture of sand substrate, the water salinity, and other factors that threaten the hawksbill turtle egg-laying place habitat. From the location of the study, it was found that the length of the beach that becomes the egg-laying place is 5000 meters and 1200 meters that do not become the egg-laying place, the beach width is about 3 – 12 meters at the highest tide and 9 – 20 meters at the lowest tide, the slope of the beach where the nest is found ranges from 10 to 15% and 8 – 11% where the nest cannot be found, the nest distance with the vegetation is about 0 – 2 meters, the air humidity is around 94,7% - 68,8%, the air temperature is about 28,830C - 330C, the nest temperature is about 28,620C, the sand substrate texture is medium with 0,21 – 0,50 µm, and the sea water salinity is 27,5%. At the location of the study there was found that every hawksbill turtle nest located in a shade of sea pandan trees (Pandanus tectorius). Hawksbill turtles are threatened by predators such as monitor lizards (Varanus salvator), ghost crabs (Ocypoda sp), fishing activities, waste bins, and natural factors such as coastal abrasion and the presence of weeds growing on the beach surface. Keyword: Habitat Characteristics, Hawksbill turtle, Tanjung Keluang Natural Park

From carrion to Christmas beetles: the broad dietary niche of the red fox in a hybrid coastal ecosystem in south-eastern Queensland

The diet of the European red fox (Vulpes vulpes) was investigated through analysis of 1185 scats collected between 2010 and 2014 from coastal south-east Queensland, Australia. By both frequency of occurrence and volume, its diet was dominated by terrestrial arthropods, marine arthropods, vegetation and birds, although the remains of the short-tailed shearwater (Ardenna tenuirostris) consumed as carrion dominated the latter. Terrestrial arthropods, primarily insects of the order Coleoptera, were eaten all year (61% frequency of occurrence, FO) but varied seasonally (35–67%FO), mostly due to the consumption of large numbers of Christmas beetles (Anoplognathus spp.) in the summer months. Marine arthropods consisted almost entirely of ghost crabs (Ocypode spp.) and seasonal variation in consumption was evident (33–72%FO) and likely correlated with ghost crab abundance. Fruit and berries were an important food item for foxes all year but also varied seasonally (30–65%FO). The opportunistic diet of this fox population is discussed in the context of dietary differences, but common opportunism, reported in other Australian and overseas studies.

Impacts of human disturbance on ghost crab burrow morphology and distribution on sandy shores.

Ghost crabs have been widely used as a bio-indicator species of human impacts on sandy beaches to obtain reliable biological data for management and conservation purposes. Ghost crab population densities and individual sizes decline dramatically under human pressure. However, distribution within a beach and the factors that determine this distribution of ghost crabs is still an open question. These factors may provide valuable information for understanding human impacts on sandy beaches. Here we examine ghost crab burrows on 20 sandy beaches of South Carolina, USA under various levels of human impacts to understand the response in terms of spatial distribution of this species to human impacts. We also examine the burrow characteristics and environmental properties of the burrows to determine whether these factors alter burrow characteristics. We show that crabs on heavily impacted beaches altered their spatial distribution to mostly occupy the edges of impacted beaches. Further, this change in spatial distribution was influenced by the size distribution of the population on a beach (i.e. larger individuals occupy upper parts on the beaches). We also found that ghost crabs altered the morphology of their burrows on heavily impacted beaches. Ghost crabs create deeper, steeper and smaller burrows under human impacts. These patterns were also influenced by physical characteristics of the beach. Our results suggest that human impacts can directly influence the spatial distribution of ghost crab populations within a beach and therefore sampling at upper parts of the beaches overestimates the population density and individual sizes. Our results support the use of ghost crabs as indicator species in effective beach management, but suggest that assessments would benefit from examining the morphology and distribution of burrows as opposed to simply using burrow counts to assess the health of sandy shores.

Multiple metrics of the ghost crab Ocypode quadrata (Fabricius, 1787) for impact assessments on sandy beaches

Our objective was to compare the efficiency of indirect (burrow density, size, depth and occupation rate) and direct (emersion from burrows, tolerance distance from humans and number of foraging crabs) metrics of the ghost crab Ocypode quadrata for urbanization impact assessments. We sampled six beaches during high and low tourism seasons along a gradient of human pressure: high impact (urbanized), medium impact (intermediate) and low impact (non-urbanized). We found that the urbanization index and temperature explained the burrow density and size regardless of the bias related to the burrow occupation rate (∼60%) and counting period (diurnal or nocturnal). Moreover, the number of nocturnal foraging crabs explained most (57%) of the dissimilarity among the beaches under different levels of human impact. Thus, the counting of foraging crabs at night was found to be a relevant metric for beach impact evaluation. We strongly recommend integrating the counting foraging crabs with traditional burrow measurements (burrow density and size) in impact assessments of sandy beaches.

Changes in the behaviour ofOcypode quadrata(Fabricius, 1787) after experimental trampling

AbstractThe effects of trampling are usually confounded by the diffuse impacts of the urbanization of sandy beaches. We performed a controlled experiment on a beach with low visitation rates to test the hypothesis that ghost crabs avoid building their burrows on impacted plots as a result of the compacted sediment, and they migrate to non-trampled areas. The sampling design encompassed 11 survey quadrats (6 × 6 m) above the strandline, including five trampled plots (100, 300, 900, 1500 and 3000 steps) and six non-trampled plots. The plots were sampled before and after 24, 48 and 72 h of experimental trampling. We found that the ghost crabs avoided building their burrows in only the 1500× and 3000× trampled plots after 24 h, but the avoidance was not related to sediment compactness. Additionally, the emersion time and escape distance from humans were significantly delayed in the most trampled plots, suggesting a lower surface activity and an avoidance of irregular (i.e. high micro-relief) sediment surfaces by ghost crabs, which might reduce their ability to perceive potential predators.

KEPADATAN KEPITING HANTU (OCYPODE) DI PANTAI BATU BEDAUN DAN PANTAI AIR ANYIR KABUPATEN BANGKA

One of the biota that lives in the sandy beach area is the Ghost Crab. These crabs are very common in the tropical and subtropical region. Bangka Regency has many sandy beaches and also a habitat spread of ghost crabs. This study aims to analyze the density of Ghost Crab (Ocypode) and the differences in the size of the carapace length with the weight of crab and the sex of the Ghost Crab in Batu Bedaun Beach and Air Anyir Beach. The results showed there were differences in ghost crab density on both beaches. Ghost Crab from Batu Bedaun 10556 individuals / km² and Air Anyir Beach 3333 individuals / km². The environmental parameters on both beaches are not much different, but in Batu Bedaun Beach has more suitable than Air Anyir Beach

Morpho-sedimentary characteristics and generated primary sedimentary structures on the modern microtidal sandy coast of eastern Nile Delta, Egypt

Spatial distribution and implication of primary sedimentary structures are combined with morpho-sedimentary features to suggest a sedimentologic–neoichnological model for the low microtidal sandy coast of eastern Nile Delta. Ten linear transects normal to the shoreline were investigated across four to five parallel geomorphic landforms. Intertidal sub-environment is characterized by abundant marine-affinity surface sedimentary structures (such as beach cusps, swash marks, air holes/volcanoes, foam impressions, raindrop imprints, rill marks and tool marks) in addition to the parallel lamination and oscillation ripples. Lower supratidal sub-environment is characterized by parallel lamination, current and wind ripples. Nebkas and wind ripples dominate the nebka/inter-nebka landforms, whereas microbial-induced sedimentary structures which including cyanobacterial mats, efflorescent salt crusts, polygonal cracks and tepee structures prevail in salinas and sabkhatized landform. Marine life-trace assemblage in the intertidal zone, belonging to infaunal and epifaunal bivalves and gastropods, resembles the poor expressions of shallow-marine Skolithos ichnofacies. Predation holes in bivalves and clavate borings in drifted tree trunks are analogous to Oichnus simplex and Teredolites isp., respectively. Transitional marine life-trace assemblage of abundant ghost crab burrows and trackways represents a modern example of seaward suites of the paleoichnological backshore Psilonichnus ichnofacies. Terrestrial life-trace assemblage of beetles, ants, vertebrate tracks and rhizoliths show similarity to the landward expression of Psilonichnus ichnofacies. Despite low to moderate preservation potentiality of modern microtidal sedimentary structures, the preserved structures are invaluable in revealing depositional processes and paleoenvironments of ancient coastal systems.

The Respiratory Compensation Point and the Deoxygenation Break Point Are Not Valid Surrogates for Critical Power and Maximum Lactate Steady State.

The Respiratory Compensation Point and the Deoxygenation Break Point Are Not Valid Surrogates for Critical Power and Maximum Lactate Steady State.

Speciation pattern of the horned ghost crab Ocypode ceratophthalmus (Pallas, 1772): An evaluation of the drivers of Indo‐Pacific marine biodiversity using a widely distributed species

AbstractAimThe high species richness of the Indo‐Australian Archipelago (IAA) marine biodiversity hotspot has been attributed to three competing hypotheses: Centre of Origin/Centre of Overlap/Centre of Accumulation. While most phylogeographic studies testing these hypotheses have focused on marine fishes, we provide a new perspective on this evolutionary important question by examining the population genetics of the horned ghost crab Ocypode ceratophthalmus sensu lato (Ocypodidae) whose distribution spans the entire Indo‐Pacific and contains at least two colour morphs.LocationIndo‐Pacific region, spanning from East Africa, India, East Asia to Central Pacific.MethodsPopulation genetics analyses based on mitochondrial COI and nuclear NaK intron sequences of O. ceratophthalmus from 39 sites throughout the Indo‐Pacific.ResultsWe found at least three genetically distinct geographical clades in O. ceratophthalmus, corresponding to the east, west and central region of the species’ range. Divergent clades were found to have originated in the peripheral Central Pacific and West Indian Ocean. Populations at the eastern margin of IAA harbour the highest genetic diversity, due to the co‐existence of east and central clades in these populations.Main conclusionsPeripheral isolation plays an important role in shaping evolutionary history of this species. Particularly, secondary dispersal of divergent lineages from the Central Pacific contributes to the high diversity found in the IAA. Thus, the Centre of Accumulation hypothesis best describes the evolutionary and demographic history of O. ceratophthalmus.

Across-shore distribution of Ocypode quadrata burrows in relation to beach features and human disturbance

ABSTRACTSpatial distribution patterns of the ghost crab Ocypode quadrata were analysed using different approaches at one disturbed and two preserved reflective sandy beaches of the Mexican Caribbean. We used spatial correlation analysis to describe the across-shore distribution of O. quadrata and their patch dynamics by beach and sampling time. In addition, we analysed the across-shore variability of habitat extent of O. quadrata (habitat envelope) and its relation to human disturbance and beach features. The spatial structure of burrow density was consistent through time, showing a bimodal distribution with very low abundance in the mid distribution range and a discrete increment of burrows to landward. Nonetheless, the size of patches varied temporally for the three beaches. Burrow size increased from seaward to landward. The location of the first burrow and the habitat envelope varied among sampling times and beaches. The location of the first burrow is mostly mediated by the swash climate, while the habitat envelope is mainly controlled by the level of human disturbance. Despite the low number of disturbed and control beaches, our results suggest that the habitat envelope could be included in future studies when using ghost crabs as indicators of human disturbance. Polynomial models and variographic analysis proved to be useful tools to describe the across-shore distribution and patch dynamics of the ghost crab.

Comparative phylogeography and genetic connectivity of two crustacean species with contrasting life histories on South Atlantic sandy beaches

The life histories of species influence the connectivity between populations, for example the dispersal potential, fecundity, and population size. We compare the phylogeography and genetic connectivity of two sandy-beach crustaceans with contrasting dispersal potentials and population traits in Brazil, based on the 16S mitochondrial gene. While the ghost crab Ocypode quadrata possesses high fecundity, long-lived planktonic larvae, and lower population densities of adults, the isopod Excirolana braziliensis is a brooder with low fecundity and higher population densities. Phylogenetic analysis of haplotype networks yielded contrasting results for the two species. Four different lineages were observed for E. braziliensis, while O. quadrata showed a low genetic structure, sharing haplotypes over ~ 7,000 km. For the isopod, the two most frequent lineages (‘North A’ and ‘South A’ lineages) showed distribution range limits that agreed with the tropical-subtropical transition of 22°S, while the others were sympatric, less frequent, and uncommon. While the ‘North A’ showed high haplotype diversity with a high structure, the ‘South A’ showed shared haplotypes and low genetic structure. Our results suggest that the contrasting life histories affect the population connectivity and genetic structure. The genetic patterns of the two species should be considered in the management and conservation of sandy-beach ecosystems.

A Reliable Bioindicator of Anthropogenic Impact on the Coast of South Carolina

Abstract Sandy beaches are frequently visited for recreational purposes. Although such recreational activities are economically beneficial, they cause disturbances to these habitats. Every ecosystem has unique properties; thus, ecosystem-specific species are often used as bioindicators of human disturbances. Here, we pioneer the use of an indirect burrow-counting technique on 20 sandy South Carolina beaches that experience different levels of human disturbance. Our results show that Ocypode quadrata (Atlantic Ghost Crab) is a reliable bioindicator of human disturbance on sandy beaches in South Carolina. The burrow density and width declined significantly as human disturbance increased. We also report that females outnumber males in highly disturbed sites. We conclude that the indirect burrow-counting technique employed in this study could minimize the cost and the effort of determining the human disturbances on coastal regions.

Vectors and reservoir hosts of covert mortality nodavirus (CMNV) in shrimp ponds.

Covert mortality nodavirus (CMNV) is the pathogen that has been identified as the cause of viral covert mortality disease (VCMD) in marine and brackish water shrimp. Recent outbreaks of this disease have resulted, and continue to result, in substantial production and economic losses to shrimp aquaculture producers in China and elsewhere. To explore potential vectors and reservoir hosts of CMNV, we collected fifteen species of invertebrates from shrimp ponds affected by VCMD. Samples were tested through the use of: reverse transcription loop-mediated isothermal amplification (RT-LAMP), reverse transcription nested PCR (RT-nPCR) followed by gene sequencing, histopathology, and in situ RNA hybridization (ISH). The results of RT-LAMP and RT-nPCR assay indicated that CMNV positive samples were identified in eleven species including brine shrimp Artemia sinica, a barnacle Balanus sp., the rotifer Brachionus urceus, the amphipod Corophium sinense Zhang, the Pacific oyster Crassostrea gigas, a hermit crab Diogenes edwardsii, the common clam Meretrix lusoria, a ghost crab Ocypode cordimundus, the hyperiid amphipod Parathemisto gaudichaudi, a fiddler crab Tubuca arcuata, and an unidentified gammarid amphipod. The alignment of CMNV RNA-dependent RNA polymerase gene sequences from eight of the species demonstrated high identities (97-100% in nucleotide sequence) with that from the original CMNV isolates of Penaeus vannamei, which suggests that these species could either be infected with, or acting as mechanical vectors of, CMNV. The CMNV infection in C. sinense, D. edwardsii, O. cordimanus Zhang, P. gaudichalldi, and T. arcuata results, to varying degrees, in vacuolation and necrosis of targeted tissues, as was verified by ISH. The infection of CMNV in these five species suggests that they might act as reservoir hosts of CMNV. The results indicate that the common species of invertebrates inhabiting shrimp ponds may constitute biological risk factors for CMNV outbreaks.

Evidence of marine debris usage by the ghost crab Ocypode quadrata (Fabricius, 1787)

Sandy beaches are sites of marine debris stranding, but the interaction of beach biota with waste is poorly studied. The objective of this study was to investigate whether the ghost crab Ocypode quadrata selects marine debris by types using a non-destructive method on sandy beaches of Southeastern Brazil. We found marine debris in 7% of 1696 surveyed burrows, and the ghost crabs selectivity was mainly by soft plastic (30%), straw (11%), rope (6%) and foam (4%). Burrows with marine debris showed higher occupation rate (~68%) compared to burrows without debris (~28%), indicating that these materials may increase the capacity of ghost crabs to memorize their burrows placement (homing). The percentage of marine debris was not always related to their amount in the drift line, but ghost crabs used more debris near urbanized areas. Future studies should test whether ghost crabs are using marine debris for feeding, homing or other mechanisms.

Like night and day: Reversals of thermal gradients across ghost crab burrows and their implications for thermal ecology

Ghost crabs, Ocypode cordimanus, inhabit relatively hostile environments subject to thermal fluctuations, including both diurnal and seasonal cycles. For many ectotherms, including ghost crabs, a major challenge is to remain cool during hot daytime temperatures. This can be achieved by adopting a fossorial lifestyle, taking advantage of thermal refuge afforded by burrows of sufficient depth. Another consideration, often overlooked, is the potential advantage associated with ready access to a thermal energy source (a “charging station”) when surface temperatures are cooler. Being able to rapidly elevate body temperature during cool periods would enhance the crab's ability to maintain rate processes and carry out essential activities. We have measured ghost crab burrow temperature profiles at two times of the day with contrasting sun exposure (06:00 and 14:00), demonstrating how effective burrow depth (up to a maximum of 40 cm) provides thermal regulation below the surface of the sand (e.g., at dawn (06:00) and early afternoon (14:00) at a depth of 5 cm, temperatures (±SD) of 16.32 ± 0.96 °C and 25.04 ± 1.47 °C were recorded, respectively. Corresponding temperatures at a depth of 30 cm were 19.17 ± 0.59 °C and 19.78 ± 1.60 °C, respectively). This demonstrates that while temperature conditions at the surface vary dramatically from night to day, ghost crab burrows can maintain relatively constant temperatures at the burrow base throughout the diurnal cycle, at least during winter. As a consequence, the burrow heat signatures undergo a corresponding thermal gradient reversal between night and day, as revealed by infra-red photography. Complementing these field observations, we also determined heating and cooling times/constants for O. cordimanus in the laboratory (τ = 17.54 and 16.59 JK-1, respectively), and analysed chemical composition of their carapace (external (with β Chitin evident) and internal (predominance of α Chitin)), which is the primary thermal interface with the environment. We find that ghost crabs both gain and lose heat relatively rapidly, which likely affects the range and duration of surface activities under different thermal conditions, and renders the thermal characteristics of their burrows vital for their persistence on beaches. Finally, we speculate that the distinctly contrasting thermal signatures of ghost crab burrows in comparison to the surrounding sand could in principle be used by crabs as spatial markers for navigation and to identify holes on return from nightly excursions, being identified either by direct thermal sensing or odours rising from the burrow base as a consequence of the thermal flux.

Presence of ghost crabs and piping plover nesting success

ABSTRACTDespite intensive management to protect the federally threatened piping plover (Charadrius melodus), breeding success in North Carolina has consistently been lower than in other Atlantic Coast states. The native ghost crab (Ocypode quadrata) preys on plover eggs and chicks, but the effect of ghost crab predation on plover productivity has not been established. We used daily records of nest survival collected at Cape Hatteras National Seashore, North Carolina, USA from 2008 to 2015 to test a hypothesized negative relationship between the presence of ghost crabs within the 3‐m diameter nest exclosure and the daily nest survival of plovers. We detected ghost crabs or their burrows within the nest exclosure on 63 out of 2,347 nest visits (24 out of 94 nests, 25%). We determined 9 nests (9.6%) were depredated by ghost crabs and 2 nests were abandoned after ghost crab visits. The estimated daily survival rate (DSR) of plover nests decreased with nest age, so to compare the nesting success predicted by our model, we standardized age in the prediction as the age at mid‐incubation. At mid‐incubation (nest age = 19 days), the DSR of a nest found with evidence of ghost crabs was 0.92 (95% CI = 0.74–0.98), compared to DSR of nests without ghost crabs (0.99, 95% CI = 0.97–0.99). We tested other covariates (e.g., clutch size, breeding timing, daily weather conditions); however, the standardized effect size of the presence of ghost crab was more than twice that of all other covariates. Ghost crabs may have a previously under‐recognized effect on plover nest survival when avian and mammalian predation is precluded by nest exclosures. Protection of piping plover nests from ghost crabs may improve piping plover nest success. © 2018 The Wildlife Society.