Population dynamics and reproduction of the hermit crab Calcinus gaimardii (Anomura: Diogenidae) at Inhaca Island,southern Mozambique

The population dynamics and reproduction of Calcinus gaimardii were studied at Inhaca Island, southern Mozambique. Crabs were sampled monthly from January to December 2003 in order to assess abundance, size distribution, sex ratio, reproduction and juvenile recruitment. Calcinus gaimardii is sexually dimorphic in relation to size, with males reaching larger size than females. Sex ratios were female‐biased during most months of the study period. Females were more abundant in the intermediate size classes while males outnumbered females in the largest ones. Reproduction took place year‐round with peaks of breeding activity between August and October. Likewise, juvenile recruitment was continuous for both sexes with high intensity in winter (May and June). Egg number increased with female size.     

Breeding season of the hermit crab Dardanus deformis H. Milne Edwards, 1836 (Anomura,Diogenidae) in Maputo Bay,southern Mozambique

The breeding season of the hermit crab Dardanus deformis is studied based on the occurrence of ovigerous females, in relation to temperature and rainfall. Monthly samples were obtained between January and December 2003 at Costa do Sol, Maputo Bay, southern Mozambique. A total of 331 female individuals was analysed of which 164 were non‐ovigerous females and 167 were ovigerous females. Dardanus deformis breeds continuously in the study area with peaks of spawning from August to October and a slight decrease from May to July. Both temperature and rainfall were positively correlated with percentages of ovigerous females. Multiple linear regressions suggest that rainfall is the main factor controlling the breeding activity of D. deformis in Maputo Bay. This species may have a rapid and high reproductive activity in the study area as observed by the higher number of ovigerous females relative to non‐ovigerous females which may contribute to a constant larval supply and recruitment of this species in the study area.     

The hermit crab Sympagurus dimorphus (Anomura: Parapaguridae) at the edge of its range in the south-western Atlantic Ocean: population and morphometry features

Sympagurus dimorphus is one of the 12 hermit crab species recorded for Argentinean waters. Despite the high abundance registered in some scallop fishing grounds, its biology remains little known. In the present study, we analysed some population features of S. dimorphus living in symbiosis with Epizoanthus paguricola from a series of samples taken in the Argentine Sea, south-western Atlantic Ocean. Our results showed that S. dimorphus was commonly found from 40ºS to lower latitudes, in a patchy distribution along the shelf-break front. The overall sex ratio was 1:1. The smallest ovigerous female measured 6 mm in cephalothoracic shield length and this size was used as parameter to define the size of juveniles. The sex ratio size class pattern corresponded to Type IV or anomalous curve. S. dimorphus is a dimorphic species, as evidenced by the larger size of the males and the positive allometric growth of the right cheliped. The species also showed asymmetry, with the left uropod always larger than the right one. To the best to our knowledge, this is the first report on population features and relative growth for a member of the genus, based on long-term sampling. This species presents a patchy distribution along the shelf-break of Argentina. Its density tended to decrease over the five-year sampling period regarding the recruitment of hermits associated with colonies of zoanthids. In addition, the relatively homogeneous nature of this refuge does not seem to influence the growth of the hermit crab, which presents sexual dimorphism in relation to the sex/size conditions.     

Population structure and breeding biology of the hairy crab Pilumnus vespertilio (Fabricius, 1793) (Crustacea: Brachyura: Pilumnidae) in southern Mozambique

The population structure and reproduction of Pilumnus vespertilio were studied for the first time in Mozambique. Random samples of crabs were taken monthly from January to December 2002 from a pebble area of Inhaca Island, southern Mozambique. A clear sexual dimorphism was observed in the present population with males reaching greater sizes than females. Sex ratio was female‐biased, and the monthly size–frequency distributions were often bimodal. The annual reproductive cycle of Pilumnus vespertilio was continuous with peaks of breeding in summer. Results suggest that embryonic development may be synchronized within the population as a result of the very high reproductive activity observed in summer. Juveniles are recruited mostly in winter in the study area.     

Relative growth and sexual dimorphism of the South Atlantic hermit crab Loxopagurus loxochelis (Anomura,Diogenidae) from Ubatuba,Brazil

Some morphometric relationships and biometric aspects were studied in the hermit crab Loxopagurus loxochelis (Moreira, 1901) with the purpose of describing its relative growth and finding the size where sexual maturity is reached. Specimens were collected monthly from September 1995 to August 1997 in the Ubatuba region using double-rig trawl nets. A total of 1084 specimens (625 males and 459 females) was analysed. In this species, sexual dimorphism is particularly evident in chela dimensions. Differences between males and females were found in the left propodus length versus cephalothoracic shield length (CSL) and wet weight (WW) versus CSL relationships. Males showed a high positive allometry in chela growth, while females were close to isometry/negative allometry. The size at which a clear differentiation occurred in the growth of the propodus length and in the increase in weight of males and females was between 4.5 and 6.0mm CSL, suggesting that size at which sexual maturity is reached.     

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.     

Population structure and reproductive biology of the fiddler crab Uca urvillei (Brachyura: Ocypodidae) in Maputo Bay (south Mozambique)

Although fiddler crabs are among the main faunal components in mangrove habitats, few studies have described the population structure and reproduction of tropical species. Such information is important for understanding their life cycle and ecology. In this study, the population structure and reproduction of Uca urvillei were studied at Costa do Sol, a tropical mangrove forest in Maputo Bay, southern Mozambique. Ten 1.0‐m² squares were sampled during low tide periods, between January and December 2003. The population is characterized by normal size distributions, which are slightly skewed to the left. Males on average are larger than females. Males were more abundant than females and the monthly sex ratios were male‐biased. Juveniles were found year‐round but were less common in June and December. Both gonadosomatic index and frequency of ovigerous females showed that Uca urvillei breeds continuously with peaks in summer and a strong decrease in winter. Egg number was proportional to female size.     

Reproductive features of the deep water hermit crab Sympagurus dimorphus (Anomura: Parapaguridae) inhabiting pseudoshells in the SW Atlantic Ocean

We herein provide information on reproductive aspects (the gonopore morphology of both sexes, the size of embryonic eggs and the fecundity) of the hermit crab Sympagurus dimorphus from deep waters of Argentina. Sampling was performed in different oceanographic and fishery campaigns between 2007 and 2010, at 38°01′–39°03′S, 55°–56°05′W, 85–150 m depth, in the SW Atlantic Ocean. Mean shield length (SL) of females was 9.41 ± 1.68 mm (range: 6.6–10.5 mm). Female gonopores measured 0.74 ± 0.10 mm (range: 0.45–0.90 mm), were oval in shape, and were more rounded and larger than male gonopores (0.51 ± 0.007, range: 0.4–0.63 mm). The egg volume for each of the three stages of embryonic development was 0.94 ± 0.20 mm³ for stage I, 1.14 ± 0.31 mm³ for stage II, and 2.07 ± 0.41 mm³ for stage III. Egg volume doubled from the initial to the final stage of the embryonic development. The fecundity (number of eggs) varied from 831 (6.62 mm SL) to 2246 (10 mm SL) for females carrying eggs in stages I+II, and between 158 (158 mm SL) and 1279 (9.4 mm SL) in stage III. The reproductive characteristics of the observed profile are intimately related to S. dimorphus use of a pseudoshell resource and a deep water habitat.     

Feeding behaviour of fifteen species of hermit crabs (Crustacea: Decapoda: Anomura) from the Otago region,southeastern New Zealand

Summary

The feeding behaviour of 15 species of hermit crabs from four families (Pylochelidae, Diogenidae, Paguridae and Parapaguridae) and from habitats ranging from rocky intertidal through continental shelf gravelly sediments to finer sediments on the shelf edge and continental slope, is described.

Feeding mechanisms found include various methods of deposit-feeding, browsing, suspension-feeding, predation and scavenging. Each species employs one or two primary feeding mechanisms but also a number of secondary mechanisms. Depositfeeding techniques include scooping up detritus-rich sediment, scrubbing detritus from the surface of small granules, scraping it from larger surfaces, picking it out of crevices and other irregularities, and brushing out and ingesting material which adheres to the general body setation. A few species browse on algae and sedentary colonial invertebrates which they slice or pluck off with the chelae. A number of species filter particles out of suspension using either the general setation of the body and/or specially modified appendages which are swept through the water. Predators either capture and ingest small organisms they encounter more or less accidentally, or actively search for prey. The latter include two species which excavate pits in the sediment in search of burrowing invertebrates. All the species studied fed upon carrion although some fed much less readily than others.

Feeding behaviour in the species studied is discussed in relation to their morphology and habitat. Previously published work on feeding in hermit crabs is reviewed. It is concluded that the broad range of feeding techniques shown by most species is probably of adaptive significance as it enables the crabs to deal with a variety of different foods and substratum types.     

Description of a new species of Asymmetrione (Isopoda: Bopyridae: Pseudioninae) infesting the hermit crab Paguristes tomentosus (Anomura: Diogenidae) from Peru,with a key to species and a review of southeastern Pacific bopyrids

A new species of bopyrid isopod is described from a host hermit crab Paguristes tomentosus collected from Pisco, Peru and assigned to the pseudionine isopod genus Asymmetrione Codreanu, Codreanu and Pike, 1965. This is the second species in the genus with less than 20° asymmetry in females, but agrees with all other species in the genus in having the characteristic “socket” on the propodus of the female's pereopods, and in all characters of the males. A key is provided to the 10 species now in Asymmetrione. New records of an Anathelges sp. from Pagurus villosus collected in central Chile are given but additional material is required to determine whether these specimens represent the eastern Pacific A. thompsoni or the western Atlantic A. hyptius. A review of all the bopyrid species known from the western South American coast, with remarks on their taxonomy and biology, is provided.     

Larval development of Clibanarius antillensis Stimpson, 1859 (Crustacea: Anomura: Diogenidae) reared under laboratory conditions: a comparison between Panamanian and Brazilian populations

The larval developmental sequences of Clibanarius antillensis Stimpson from first zoea through to megalopa are compared between laboratory-reared populations from Panama and Brazil. Only four zoeal stages are recorded for the Panamanian population, in contrast to four or five for the Brazilian larvae. Other differences in morphology are discussed and illustrated. Variations resulting from geographic differences and/or differing laboratory conditions raise the question of the validity of phylogenetic hypotheses based on single laboratory rearing events.     

Description of Ghatiana,a new genus of freshwater crab,with two new species and a new species of Gubernatoriana (Crustacea: Decapoda: Brachyura: Gecarcinucidae) from the Western Ghat Mountains,India

A new genus of freshwater crab, Ghatiana, with two new species, Ghatiana aurantiaca and Ghatiana hyacintha, and a new species of Gubernatoriana Bott, 1970, are described from the Western Ghat Mountains in Maharashtra State, India. Ghatiana is most similar to Gubernatoriana by its wide, highly arched carapace and by the shape of the male abdomen. Nevertheless, the new genus can be distinguished from Gubernatoriana by the broadness of carapace, length of male abdomen, shape of sixth abdominal somite, length of telson and length of G1 terminal article. Ghatiana aurantiaca sp. nov. and G. hyacintha sp. nov. are distinguished by differences in body colour, carapace width, and G1 morphology, whereas Gubernatoriana triangulus sp. nov. is distinguished from two other known species [Gubernatoriana gubernatoris (Alcock, 1909) and Gubernatoriana pilosipes (Alcock, 1909)] by its triangular G1 subterminal segment and by its carapace morphology. Keys to the species of both the genera are provided.

http://www.zoobank.org/urn:lsid:zoobank.org:pub:36BAA1EA-DC15-4B06-BA09-7BD26C63FF54     

Breeding biology and population structure of the intertidal crab Petrolisthes laevigatus (Anomura: Porcellanidae) in central-southern Chile

The present study describes the seasonal reproductive cycle and population structure of the porcellanid crab Petrolisthes laevigatus, a typical inhabitant of the rocky intertidal. A total of 960 individuals (including 372 females) was collected in monthly samples from October 1993 to December 1994 in central-southern Chile. Ovigerous females were present between August and December, and were absent between January and July. The breeding season started during late winter (August), and females with embryos close to hatching occurred between October and end of spring (December). Considering the gonadosomatic index and the duration of the incubation period, it is concluded that P. laevigatus has a markedly seasonal breeding period with probably two successive spawnings per female per season. Our results compared with previous studies in temperate intertidal porcellanids suggest a lower structural variability of the population during the sampling period, but a pronounced seasonal variation in both sex ratio and abundance. The influence of environmental habitat conditions (i.e. temperature) is suggested to be responsible for the lower variation in the crab population size structure in ovigerous females, and the almost constant size distribution observed in males.     

Revision of the sesarmid crab genera Labuanium Serène and Soh, 1970, Scandarma Schubart,Liu and Cuesta, 2003 and Namlacium Serène and Soh, 1970 (Crustacea: Decapoda: Brachyura: Sesarmidae), with descriptions of four new genera and two new species

ABSTRACT

The systematics of the arboreal sesarmid crab genera Labuanium Serène and Soh, 1970 and Scandarma Schubart, Liu and Cuesta, 2003 is revised. Also included is the poorly known genus Namlacium Serène and Soh, 1970, which is morphologically similar to Labuanium and may also be arboreal in habit. The present study restricts Labuanium to its type species, L. politum (De Man, 1887), and congeners are transferred to Scandarma, Geosesarma De Man, 1892, and three new genera established herein: Circulium gen. nov., Shinobium gen. nov. and Mindanium gen. nov. Two new species of Scandarma are described from Papua New Guinea and Madagascar. Sesarma jacquinoti Ortmann, 1894, previously regarded as a synonym of Scandarma gracilipes (H. Milne Edwards, 1853) (comb. nov.), is here shown to be a junior synonym of Sesarmops angustifrons (A. Milne-Edwards, 1869). Labuanium schuetteii (Hess, 1865) is regarded as conspecific with Scandarma gracilipes (H. Milne Edwards, 1853) (comb. nov.) and the lectotype of the latter species (here designated) is also selected as the neotype of the former, making the two names objective synonyms. Material which had been identified as ‘Labuanium finni Alcock, 1900’ by Pretzmann (1984) from the South Andaman Islands is actually the poorly known Geosesarma thelxinoe (De Man, 1908), which is here referred to a new genus, Andamanium gen. nov. Sesarma finni Alcock, 1900 s.s. is herein assigned to Scandarma. Namlacium crepidatum (Calman, 1925), the only species in the genus, is redescribed and figured and compared with Labuanium and Scandarma. Keys to species of Circulium and Scandarma are provided.

http://www.zoobank.org/urn:lsid:zoobank.org:pub:414B8DAA-584F-4070-A355-83B583D0D017     

A new genus and species of pinnotherid crab from Karachi,northern Arabian Sea (Crustacea,Decapoda, Brachyura)

A new monotypic genus, Sindheres, is established to accommodate a new species, S. karachiensis, of pinnotherid crab from the northern Arabian Sea. The new genus resembles Nepinnotheres Manning, 1993 in having the dactylus of the third maxilliped inserted near the mid-length of the ventral margin of the propodus but it differs in having a sub-hexagonal carapace.     

Population structure of Tachypleus tridentatus (Chelicerata: Merostomata) at a nursery beach in Puerto Princesa City,Palawan, Philippines

This study aimed to determine the population structure of juvenile Tachypleus tridentatus, one of two species of horseshoe crabs found in Palawan, at Aventura Beach, Puerto Princesa City, Palawan. Surveys to assess the population in terms of size, density, size‐frequency, age structure, sex ratio and distribution were conducted from June to October 2002. The habitat was mapped and physical/chemical parameters taken to further describe it. The position of population members was plotted on the map. Individuals were measured, marked, sexed and released. Prosoma width was measured for living individuals and exuviae. Postembryonic stages were identified based on histograms with different interval size. The normal distribution of the animals per instar stage was tested with the Kolmogorov–Smirnov test. After the 5‐month survey a total of 125 juveniles was recorded and 40% of them were recaptured. Population size was estimated to be 150 individuals. Seven postembryonic stages were identified based on their prosoma width. Male: female ratio was 1:1.8 and the age of the first five postembryonic stages ranged from 5.4 months to 17.6 months. The population density was 1.47 individuals per?100?m². The majority of the animals of all postembryonic stages were found between 0 and 50?m from the mean high tide level. Further studies on the population structure of T. tridentatus with regards to the adult population are seen as a necessity.     

Vocalization and territorial behaviour of Phyllomedusa nordestina Caramaschi, 2006 (Anura: Hylidae) from southern Bahia,Brazil

Territoriality is common among amphibians with a prolonged breeding season and can be expressed through the defence of territories with vocalizations and aggressive interactions. The present study aims to describe the territorial behaviour of male Phyllomedusa nordestina, test whether the physical characteristics of males influence the results of disputes, and describe the vocalizations of the species. The study was conducted at temporary and permanent ponds located in the Ecological Reserve Michelin, Igrapiúna, Bahia, Brazil. Male P. nordestina defended territories and showed aggressive behaviour, consisting of vocal disputes, chasing and physical fighting. Winners were not bigger, heavier, or in better condition than the losers. The victory may be associated with the vocalization activity. Three types of vocalizations were recorded: the advertisement call, composed of one or two multipulsed notes, and two types of territorial calls. We also report on male patrolling behaviour and habitat use.     

A report on two large collections of the squat lobster Munidopsis platirostris (Decapoda,Anomura, Munidopsidae) from the Caribbean,with notes on their parasites,associates, and reproduction

The reproduction and parasite associates of the squat lobster Munidopsis platirostris (A. Milne Edwards and Bouvier, 1894) were investigated based on collections made in the Bahamas and Curaçao with grassmat and bundled fishing net traps used to collect sipunculan worms and other small invertebrates. Size of ovigerous M. platirostris was significantly correlated with clutch size for females from both localities but females from the Bahamas produced significantly more eggs (on average 10.1 eggs/clutch) than females from Curaçao (on average 6.6 eggs/clutch). Early embryos of M. platirostris from the Bahamas were 0.74–0.82 mm in diameter, similar to some other species of Munidopsidae as well as Chirostylidae. Two species of crustaceans, another squat lobster and a leptostracan, as well as a limpet mollusc, were collected with M. platirostris in the Bahamas, while a sipunculan was an associated species in a Curaçao collection. One specimen of M. platirostris had an unidentified cryptoniscoid epicaridean isopod, possibly representing a new genus and species. Two specimens of M. platirostris each had one rhizocephalan externa of a species belonging to Lernaeodiscus Müller, 1862 but their morphology does not match that of L. schmitti Reinhard, 1950, the only species in the genus known from squat lobsters in the western Atlantic. Additional materials and tools, such as DNA analysis, are needed to describe these potentially new parasites and we suggest that use of these traps may be an effective method to obtain additional samples.