A new species of micro-mangrove crab of the genus Haberma Ng & Schubart, 2002 (Crustacea, Brachyura, Sesarmidae) from Hong Kong

The sesarmid genus Haberma Ng & Schubart, 2002, currently contains two species of small mangrove crabs with the first two pairs of the male ambulatory legs possessing characteristic subchelate dactyli and propodi. A new species, H. tingkok, is here described from Hong Kong. It can be separated from H. nanum Ng & Schubart, 2002 (from Singapore), and H. kamora Rahayu & Ng, 2005 (from Indonesian Papua) by its carapace shape, proportions of the ambulatory legs, and structures of the male pleon and male first gonopod.published_or_final_versio

Feeding specialization and activity in certain mangrove crabs

Decapoda is surely one of the most important taxa, both regarding the number of species and individuals, in the macrofauna of the mangrove ecosystem (Macnae, 1968; Macintosh, 1988). For this reason, knowledge about their feeding habits and diet is of primary importance for understanding the energy flow typical of this ecosystem.In Mida Creek and Gazi Bay (Kenya) we collected and then analysed the stomach contents of about 350 crabs belonging to the most common mangrove crab species (excluding the Uca species whose micro-algal feeding habits were already known): Cardisoma carnifex, Epixanthus dentatus, Eurycarcinus natalensis, Metopograpsus oceanicus, M. thukuhar, Sesarma elongatum, S. guttatum, S. leptosoma, S. meinerti, S. ortmanni, Thalamita crenata.Species were divided into classes according to the animal/vegetable matter ratio of their stomach contents.The average stomach fullness proved to be correlated with the degree of vegetable content, being lower in the carnivorous species.Stomach analysis showed that only a few species were strictly herbivorous (mostly feeding on leaf litter) or strictly carnivorous (ambush predators of molluscs or crabs). Instead, magrove crabs seemed to be generally omnivorous, probably due to the low energy and protein content of the food commonly found and to the difficulties in catching suitable prey.For Thalamita crenata, a predator inhabiting the intertidal platform in front of the mangroves, it was also possible to analyse the feeding activity in relation to the different conditions of tide and light. Its feeding activity was higher during the day than at night, and it also seems to feed during low tide, probably catching prey during ebb tides and consuming them when it hides in its shelter

Homing in the mangrove swimming crab <i>Thalamita crenata</i> (Decapoda: Portunidae)

Thalamita crenata is a swimming crab which commonly lives in the shallow waters of sheltered shores of the whole Indo-Pacific region. On the Kenyan coast, this species colonises the intertidal plateau in front of the mangrove. This crab proved to be faithful to a familiar area in which it visited a small number of known holes where it hides during low tide (Vezzosi et al., in prep.). The aim of this study was to test the homing ability of T. crenata after being passively displaced both within the supposed familiar range (internal homing) and outside it (external homing)

Characterisation of the crab <i>Neosarmatium meinerti</i> de Man (Decapoda: Sesarminae) predation on <i>Avicennia marina</i> propagules

Mangrove forests are essential for coastal and reef protection. It is an ecosystem providing protection from sedimentation and a range of goods and utilities for local population (Walters et al., 2008). Avicennia marina is a pioneering mangrove species. This tree plays an important role in the colonization and the recolonization of mangroves (Osborn and Beriak., 1997) as it is one of the first species to settle in unforested and deforested areas (loc. cit.). Neosarmatium meinerti is a herbivorous crab, feeding essentially of leaves fallen on the ground and propagules (Dahdouh-Guebas et al., 1997). The propagule predation has a direct impact on mangrove regeneration (Bosire et al., 2005) and therefore on their dynamics. In this perspective we intend to characterize this predation and assess its impact on mangrove forest dynamics and especially on Avicennia marina. We focus on the time and amount of propagules predated upon and on interactions amongst the predators during feeding

Fate of the predictions in Galle-Unawatuna mangroves, Sri Lanka: A validation after 10 years using satellite (IKONOS) and ground-truth data

Validation of earlier predictions is a challenging but significant contribution to ecological research. The present study tests the predications made 10 years ago by Dahdouh-Guebas et al. (2000) on the evolution of mangrove forest in Galle-Unawatuna, Sri Lanka. The ground inventory carried out in five Sectors covering the entire forest (Point Centred Quarter Method - PCQM) (Cintron and Schaeffer Novelli, 1984) revealed that the adult species composition is dominated by Rhizophora apiculata, Excoecaria agallocha, Bruguiera gymnorrhiza and B. sexangula, with their total density of 216-267 stems 0.1ha-1 and basal area 1.19-1.44m2 0.1ha-1. However, both young and juvenile vegetation in the most Sectors was dominated solely by B. gymnorrhiza (128-869 stems and 356-1482 propagules 0.1ha-1). According to Dahdouh-Guebas et al. (2000), the transition of an E. agallocha forest into a B. gymnorrhiza dominated one or at least their co-dominance in the Sectors 1 and 2 is possible, whereas Sector 3 being dominated by adult and juvenile R. apiculata will persist. Overall, the possible transition to a Bruguiera dominated forest in Galle-Unawatuna area was forecasted. The recent decadal changes between 1994 and 2004 through the integration of IKONOS satellite imagery of 2004 with ground-truth information confirmed many of the predictions and showed dynamic shifts in young/adult vegetation by B. gymnorrhiza. Both E. agallocha and R. apiculata continue to be dominant in Sectors 2 and 3, although the adult turnover by B. gymnorrhiza has not yet occurred, probably due to the small time interval between the two investigations. Confirming in part with the earlier prediction on R. apiculata in Sector 3, present study also revealed the abundance of B. gymnorrhiza as young and juvenile vegetation. Viewing the present dynamic shifts and sheer dominance as young vegetation by B. gymnorrhiza with a mean height of 5.8m in most Sectors, it is still possible to anticipate the mangroves being dominated by this species, and actually now validates the predictions made 10 years ago. Because of apparent changes in the mangrove vegetation structure, it could be concluded that the ‘moving mosaic’ pattern of mangrove species distribution reported earlier for Galle-Unawatuna still persists

Feeding spectra and activity of the freshwater crab Trichodactylus kensleyi (Decapoda: Brachyura: Trichodactylidae) at La Plata basin

Background: In inland water systems, it is important to characterize the trophic links in order to identify the ‘trophic species’ and, from the studies of functional diversity, understand the dynamics of matter and energy in these environments. The aim of this study is to analyze the natural diet of Trichodactylus kensleyi of subtropical rainforest streams and corroborate the temporal variation in the trophic activity during day hours. Results: A total of 15 major taxonomic groups were recognized in gut contents. The index of relative importance identified the following main prey items in decreasing order of importance: vegetal remains, oligochaetes, chironomid larvae, and algae. A significant difference was found in the amount of full stomachs during day hours showing a less trophic activity at midday and afternoon. The index of relative importance values evidenced the consumption of different prey according to day moments. Results of the gut content indicate that T. kensleyi is an omnivorous crab like other trichodactylid species. Opportunistic behavior is revealed by the ingestion of organisms abundant in streams such as oligochaetes and chironomid larvae. The consumption of allochthonous plant debris shows the importance of this crab as shredder in subtropical streams. However, the effective assimilation of plant matter is yet unknown in trichodactylid crabs. Conclusions: This research provides knowledge that complements previous studies about trophic relationships of trichodactylid crabs and supported the importance of T. kensleyi in the transference of energy and matter from benthic community and riparian sources to superior trophic levels using both macro- and microfauna.Fil: Williner, Verónica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina. Universidad Nacional del Litoral. Facultad de Humanidades y Ciencias; ArgentinaFil: de Azevedo Carvalho, Debora. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; ArgentinaFil: Collins, Pablo Agustin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto Nacional de Limnología. Universidad Nacional del Litoral. Instituto Nacional de Limnología; Argentina. Universidad Nacional del Litoral. Facultad de Bioquímica y Ciencias Biológicas; Argentin