Description of a new species of Demania Laurie, 1906 (Crustacea,Decapoda, Brachyura,Xanthidae) from the Bay of Bengal,Indian Ocean

A new species of xanthid crab, Demania bangladeshensis sp. nov., is described from the Bay of Bengal, Indian Ocean. Demania bangladeshensis appears to be most closely related to Demania toxica Garth, 1971, a poisonous species from the Philippines, but can easily be separated by the differently sculptured carapace, legs and chelipeds.     

Sound production in primitive Orthoptera from Western Australia: sounds used in defence and social communication in Ametrus sp. and Hadrogryllacris sp. (Gryllacrididae: Orthoptera)

Sound production in two undescribed species of Gryllacrididae belonging to the genus Ametrus sp. and Hadrogryllacris sp. takes the form of defensive stridulation and intra-specific signalling by drumming on the substrate. Defensive stridulation is produced as part of an elaborate visual display, by femoro-tergal stridulation. Two rows of spines on abdominal tergites II and III of both species are rubbed by an elongate area of tubercules on the inner femoral surface of the hind legs. Analysis showed that the motion of the leg relative to the abdomen involves a complex counter-rotation of the leg between leg and abdomen. The defensive display may be performed in day light. Social signalling in both species occurs after dark, and involves drumming on the substrate by both hind legs in loose synchrony. Drumming is rhythmic and species' specific. Males respond to playback calls and females duet with males. The evolution of this calling behaviour is discussed and comparisons are made with the other primitive ensiferan family known to produce both tergo-abdominal defensive stridulation and femoral drumming behaviour, the Stenopelmatidae.     

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

Spatial 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.     

Spatial distribution of the ghost crab Ocypode quadrata in low‐energy tide‐dominated sandy beaches

The spatial distribution of the ghost crab Ocypode quadrata (Crustacea, Brachyura) was described in five low‐energy tide‐dominated sandy beaches in São Sebastião Channel (Grande, Zimbro, Pitangueiras, Cabelo Gordo, and Segredo). On each beach, the zonation study was performed on five random 1?m wide transects sampled from the water line to the vegetation. In general, individuals occurred above 1?m in height in relation to mean low water (MLW) and peaked between 1.5 and 2.0?m. The sandy beaches were then divided into three 1?m wide strips (tidal levels) parallel to the water line and equivalent to medium intertidal, upper intertidal, and subterrestrial fringe to test the effect of beach and tidal level on the abundance and size of O. quadrata. These strips were sampled as a whole using adjacent 1 m² squares. A previous evaluation showed a positive significant relationship between carapace length and burrow diameter, thus supporting crab size estimates from burrow openings. The smallest individuals occurred mainly in the medium intertidal, but were also recorded in the subterrestrial fringe, which was occupied mainly by large‐sized individuals. In general, the individuals were randomly dispersed within the strips and concentrated in the upper intertidal zone on all the sandy beaches. The density of O. quadrata varied among beaches, with a tendency to lower values on areas with very fine and poorly or moderately sorted sediments and on that most used for recreational activities (Grande). Burrow size also varied among beaches, with a tendency of smaller burrows in areas with coarser sand grains and higher tourism. These results indicate that the effect of human impact on density and size of O. quadrata may be confounded by the high environmental heterogeneity of the studied system, which may make it difficult to utilize this species as an indicator of the conservation status of low‐energy tide‐dominated sandy beaches.     

Intertidal distribution,symbiotic association and reproduction of Pinnotheres bidentatus (Brachyura: Pinnotheridae) from Taiwan

The intertidal distribution of the free-swimming stage of the pea crab Pinnotheres bidentatus Sakai, 1939 was examined on the Kaomei coastal flat of western central Taiwan. Most pea crabs were collected from tidal waters close to the shoreline regardless of the collecting treatments utilized. Results suggest that the pea crab population remains inshore during ebb tides. Many hard and post-hard stages of P. bidentatus were discovered, including ovigerous females. The host was found to be Laternula marilina (Valenciennes, 1860) (Mollusca: Bivalvia: Laternulidae). The infestation percentage of the bivalve was high (average 74.6%). However, this may be due to collections of the bivalve population in the present study being skewed towards large sizes. This biased size structure of the host population may be also responsible for lack of positive size correlation between number and size of male and female symbiotic crabs and the host. Multiple infestations of P. bidentatus appear to be uncommon for L. marilina. Single infestations might be a model for bivalves in tropical regions where the sea is relatively oligotrophic and food competition may be enhanced with multiple infestations. In comparison to other members of the genus Pinnotheres or related species (e.g. P. pisum (Linnaeus, 1767) and Zaops ostreum (Say, 1817)), the body size of sexually mature female P. bidentatus is relatively small, even though it produces similar size eggs (approximately 300 microns). The general rule for size correlation between fecundity and female size in brachyuran crabs holds for P. bidentatus.     

Ectosymbionts of the non‐indigenous Asian shore crab,Hemigrapsus sanguineus (Decapoda: Varunidae), in the western north Atlantic,and a search for its parasites

Over 560 Asian shore crabs, Hemigrapsus sanguineus, collected mainly in the spring of 2005 and 2006 from rocky intertidal locations in southern New Jersey, were examined for epibionts. Small numbers of the sympatric green crab, Carcinus maenas, and the Atlantic mud crab, Panopeus herbstii, were examined for epifauna to compare with H. sanguineus. Blue mussel spat, Mytilus edulis, and the encrusting, cheilostome bryozoan, Conopeum tenuissimum, were the dominant ectosymbionts of the shore crab, with prevalences of 22.2 and 32.1%, respectively; ranges of intensity were 1–146 spat/crab and 1–31 colonies/crab. Both species are incidental symbionts. Larger crabs had higher prevalences and intensities of C. tenuissimum colonies, and these colonies displayed a distinct pattern of attachment to the carapace which seemed to be related to crab morphology and habitat. Much less common was the encrusting, ctenostome bryozoan Alcyonidium albescens, a facultative symbiont species with a prevalence of 3.4%. Other epibionts were the encrusting, cheilostome Membranipora tenuis, the tubicolous polychaetes Hydroides dianthus, Sabellaria vulgaris, and Spirorbis sp., the barnacles Balanus improvisus and Semibalanus balanoides, and unidentified thecate hydroids, all incidental symbionts with prevalences from 0.2 to 3.2%. The total number of known ectosymbionts of H. sanguineus, including additional species found previously in the USA and the western Pacific, is 13. Carcinus maenas and P. herbstii share some of the same symbionts. Rhizocephalan externae were not observed in any of the crab species used in this study, nor were gill parasites or internal parasites found among 248 specimens of H. sanguineus.     

A comparative study of the larval development of Monodaeus couchi (Couch), Xantho incisus Leach and Pilumnus hirtellus (Linnaeus) (Crustacea: Brachyura: Xanthidae)

Summary

Comparative accounts are given of the larval and first crab stages of three crab species belonging to the family Xanthidae: Monodaeus couchi (Couch), Xantho incisus Leach and Pilumnus hirtellus (Linnaeus). Features are discussed that distinguish the larvae of these species from those of other N.E. Atlantic brachyrhynch crabs.     

The larval and post-larval development of Gibbs's spider crab,Pisa armata (Latreille) [family Majidae: subfamily Pisinae], reared in the laboratory

Summary

The larvae and first crab stage of the spider crab Pisa armata are described from laboratory reared material. The larval stages are compared with previous accounts and with those of Pisa tetraodon. Larval affinities with other genera of Pisinae are discussed.     

Juvenile development and growth patterns in the mud crab Eurytium limosum (Say, 1818) (Decapoda,Brachyura, Xanthidae) under laboratory conditions

The post‐larval development of the mud crab Eurytium limosum was studied under laboratory conditions by using the offspring of ovigerous females collected at the Comprido River mangrove, SP, Brazil. The first crab stage is fully described and the juvenile development, until crab stage 10, is examined with emphasis on morphological change, sexual differentiation and growth patterns. The carapace of the first crab stage is nearly square as observed in other xanthids, becoming similar to adults only at stage 15. The sexes can be distinguished from stage four, based on the number of pleopods and their morphology. While the intermoult period increases, the moult percentage decreases at each stage. The abdominal allometric growth is sex‐dependent, with males showing a negative (b?=?0.71) and females an isometric (b?=?0.95) relative growth pattern. Male gonopods undergo a positive allometric growth, and their shape changes remarkably until sexual maturity. The cheliped dentition can be observed after stage 4. Regardless of sex, most crabs have a molariform right cheliped, which is thought to aid the handling of asymmetric prey such as gastropods.     

Symbiotic associations between hermit crabs and bryozoans from the Otago region,southeastern New Zealand

Thirteen species of bryozoans (six cyclostomes and seven cheilostomes) occurring off the Otago Peninsula (southeastern New Zealand) form symbiotic, possibly mutualistic, associations with hermit crabs. For all but one of these bryozoan species, such an association has not been reported previously. At most only 3 of the 13 bryozoans are obligate symbionts of hermit crabs. Associations are apparently initiated when a bryozoan larva settles on a gastropod shell occupied by a juvenile hermit crab and develops to form a colony which encrusts the whole shell and then continues to grow out beyond the shell aperture in the form of a helicospiral tube. The tube-building bryozoan colony grows in step with the crab, and tube development appears to be controlled by crab morphology and activity. Of the six species of hermit crabs found occupying bryozoan tubes, four were regular tube occupants, although they could also be found in other shelter types. Hermit crabs occupying bryozoan tubes very rarely indulged in shell exchanges or shell fights. There appear to be no clear cut pairwise correlations between hermit crab species and tube-forming bryozoan species. The following bryozoan species are described for the first time: Heteropora parapelliculata, Borgiola otagoensis, Disporella gordoni, Osthimosia monilifera and O. socialis.     

Natural diet of fish and crabs associated with the phytal community of Sargassum cymosum C. Agardh, 1820 (Phaeophyta,Fucales) at Ponta das Garoupas,Bombinhas, Santa Catarina State,Brazil

The diet of fish and crabs associated with Sargassum cymosum beds was analysed at Ponta das Garoupas, Santa Catarina State, southern Brazil. They are reported to feed on phytal organisms. The relative importance of food items was established for these consumers, and the frequency of occurrence and volumetric methods were used for quantitative analysis. The analysis of 272 guts from 11 fish and two decapod species revealed that eight fish and one crab species had phytal organisms as important items in their diet. Amphipods and molluscs were the main phytal animals in the diet of these fish and the crab; notably Caprella scaura, Hyale media, Atylus minikoi, Tricolia affinis and Bittium varium. Commercially important fish, such as the grouper Epinephelus guaza, feed on these fish and crabs, showing that Sargassum beds constitute an important link between benthic autotrophic producers and several levels of consumers on rocky shore ecosystems at Ponta das Garoupas.     

Complex display behaviour during the intraspecific interactions of myrmecomorphic jumping spiders (Araneae,Salticidae)

Jumping spiders (Salticidae) are known for their elaborate vision‐based display behaviour, and a sizeable minority of the species in this large family resemble ants. The display repertoire of two ant‐like salticid species from the Philippines is investigated. Myrmarachne assimilis is a specialist ant mimic, closely matching the appearance of the weaver ant Oecophylla smaragdina. Myrmarachne bakeri is a generalist mimic, which, although ant‐like, is not a close match to any sympatric ant species. Myrmarachne are sexually dimorphic, with males having enlarged chelicerae. The copulatory posture of Myrmarachne is unique among salticids, apparently as an adjustment for the male's elongated chelicerae. Details concerning the intraspecific behaviour of Myrmarachne appear to be adjustments to living in environments populated by numerous other animals with similar appearance (ants). However, the specialist and the generalist that were investigated have display repertoires that are broadly similar to each other and to those of more typical salticids. Generally, the display behaviour of Myrmarachne appears not to have necessitated dramatic deviation from typical salticid display and mating strategies.     

Larval development and emigration behaviour during sea-to-land transition of the land hermit crab Coenobita brevimanus Dana, 1852 (Crustacea: Decapoda: Anomura: Coenobitidae) under laboratory conditions

To determine the early life history of the land hermit crab Coenobita brevimanus Dana, 1852, larvae were cultured individually in the laboratory. The zoeal and the megalopal stages are described and illustrated. The larvae developed through four planktonic zoeal stages to the megalopal stage. The major differences in the zoeal characters between C. brevimanus and other described Coenobita species were found in the armature of the pleomeres, whereas the character of pleomeres of C. brevimanus zoeae is the same as that of the coconut crab Birgus latro, a different genus in the same family. Morphological similarity was also found in segmentations of antennules and antennae in megalopae between C. brevimanus and the coconut crab. Megalopae of C. brevimanus were cultured in containers holding seawater and a hard substrate. These crabs migrate from the sea to land after developing a habit of acquiring gastropod shells.     

Aggressive,omnivorous, invasive: the Erythraean moon crab Matuta victor (Fabricius, 1781) (Crustacea: Decapoda: Matutidae) in the eastern Mediterranean sea

Since its first sighting in 2012 in Haifa Bay, Israel, the population of the Indo-Pacific moon crab, Matuta victor, has increased greatly along the Israeli littoral and spread to Lebanon and the Mediterranean coast of Turkey. To examine possible interactions with the Levantine nearshore psammophilic community, the crab’s feeding behaviour was observed in situ and the foregut contents of 69 specimens collected in December 2015 and June 2016 were analysed. Its omnivorous diet was confirmed and previously unknown intraspecific competitive feeding behaviour is reported. The agonistic behaviour may denote behavioural flexibility that enables the crabs to colonize and persist in a depauperate novel habitat. Site-specific disturbance regimen related to human activities seems to have had a critical role in driving the rapid population increase.     

The complete larval development of the Mangrove Ocypodid crab Macrophthalmus depressus Ruppell, 1830 (Brachyura: Macrophthalminae) reared in the laboratory

Macrophthalmus depressus larvae were reared in the laboratory using filtered estuarine water of salinity 25±1 ppt and temperature 29–31°C. M. depressus reaches the first crab stage after passing through five zoeal and a megalopa stage requiring 22–23 days. Each stage is described in detail and compared with other known species of the genus.     

Aspects of mangal ecology along the Red Sea coast of Saudi Arabia

Surveys of the mangal along the Red Sea coast of Saudi Arabia form the basis of this study. Both soft-bottomed mangals and the less well known hard-bottomed mangals are represented. The distribution of Avicennia marina, the dominant mangrove species, is discontinuous in the northern part of the Red Sea. Its development increases southwards, and mean height is inversely correlated both with latitude (P<0·05) and salinity (P<0·05). Another species, Rhizophora mucronata, was recorded in only five areas. Molluscs and crabs represent the principal faunal elements within the mangal. The density of Cerithidea cingulata, the dominant mollusc species, shows significant correlation (P<0·01) with the abundance of blue-green algae. Four species of fiddler crab (Uca) are included among the crab fauna of the mangal, one of which (U. urvillei) is here newly recorded for the Red Sea. Evidence is given for suggesting that the mangal biota in the region sampled may not be distinctive. Rather, it consists of many species found not only within the mangal but also in other habitats such as seagrass beds and even rock beaches. It is suggested that the mangal of the Red Sea represents a composite habitat, containing both hard and soft substrates and inhabited by species typical of each. This contrasts with the situation in most other mangals studied.     

Distal leg morphology,subgenual organs and host detection in Stephanidae (Insecta,Hymenoptera)

The morphology of the tibia and tarsus of all legs is examined in species of two genera of Stephanidae. The subgenual organ (SGO) is examined in more detail for Megischus spp. The fore leg is the most modified in Schlettererius. In Megischus, the SGO of the hind leg is displaced to the middle of the tibia, which is swollen distad of it; in the female the hind tarsi are three‐segmented, the basitarsomere being a composite of tarsomeres 1–3. Internally, the SGO of Megischus is suspended between a spine and a ridge. In the mid and hind legs, part of the tibial wall is thinner in the region of the SGO. Our observations provide circumstantial evidence that female Stephanidae detect substrate‐borne vibrations when searching for hosts. The absence of antennal modification, as well as information on host stage targeted and general behaviour on the oviposition site indicates that they rely on noise made by the host rather than generate vibrations themselves, in contrast to Orussidae, a parasitoid wasp taxon that has been inferred to employ vibrational sounding. The external receptor elements – membranous pads versus tufts of setae – are not homologous in Orussidae and Stephanidae. A spine and ridge suspensorium of the SGO found in members of both families may represent a derived groundplan feature of the orussid–apocritan clade, with secondary modification or reduction in the latter group. Characters of the distal leg elements and the SGO suggest a basal position of Schlettererius and Stephanus within Stephanidae. Modifications of the hind tibia and tarsus in more derived members of the family indicate a shift in relative importance in vibration detection from the fore leg to the hind leg within the family.     

On a new genus and new species of xanthid crab (Crustacea,Decapoda, Brachyura,Xanthinae) from the South China Sea,with notes on the genus Liagore De Haan, 1833

A new genus and new species of xanthid crab, Ovatis simplex, is described from the South China Sea. The genus is closest to Liagore but can be distinguished by a suite of carapace and male gonopod characters. The systematic position of Liagore is also considered, and both genera, Liagore and Ovatis, are here referred to the subfamily Xanthinae. Comparisons with the allied genera, Paratergatis and Pulcratis, are also provided.