Predation on the Treefrog Boophis Rufioculis (Anura, Mantellidae) by the Freshwater Crab Hydrothelphusa Sp
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Crustaceana 87 (7) 890-894 PREDATION ON THE TREEFROG BOOPHIS RUFIOCULIS (ANURA, MANTELLIDAE) BY THE FRESHWATER CRAB HYDROTHELPHUSA SP. (DECAPODA, POTAMONAUTIDAE) IN MADAGASCAR BY GONÇALO M. ROSA1,2,3,6), JOANA SABINO-PINTO3), JEAN NOËL4) and FRANCO ANDREONE5) 1) Durrell Institute of Conservation and Ecology, School of Anthropology and Conservation, University of Kent, Canterbury, Kent CT2 7NR, U.K. 2) Institute of Zoology, Zoological Society of London, Regent’s Park, London NW1 4RY, U.K. 3) Centro de Biologia Ambiental, Faculdade de Ciências da Universidade de Lisboa, Bloco 2, Piso 5, Campo Grande, 1749-016 Lisbon, Portugal 4) Madagascar Fauna & Flora Group, BP 442, Morafeno, Toamasina 501, Madagascar 5) Museo Regionale di Scienze Naturali, Sezione di Zoologia, Via G. Giolitti, 36, I-10123, Torino, Italy Freshwater crabs are found throughout inland waters within the tropical and warm temperate zones of the world. They produce eggs that develop directly into hatchling crabs, in contrast to their marine relatives who produce thousands of eggs that develop into planktonic larvae. In Madagascar, all primary freshwater crabs that live in the freshwater ecosystems belong to the family Potamonautidae Bott, 1970 (Cumberlidge & Sternberg, 2002; Ng et al., 2008). This monophyletic family is endemic to the Afrotropical region (Cumberlidge, 2008) and includes 142 species within 18 genera, of which the Malagasy freshwater crab fauna com- prises 15 species in 7 genera. The genus Hydrothelphusa comprises 4 species dis- tinguishable by the morphological character of the carapace, sternum, mouthparts and gonopods (Cumberlidge & Sternberg, 2002; Cumberlidge et al., 2007; Cum- berlidge & Meyer, 2009). With few exceptions, freshwater crabs are generally omnivores, eating vegetable matter, live invertebrate prey, and even small vertebrates (Ng, 1988; Dobson, 2004; Cumberlidge et al., 2009). The predation of anurans by freshwater crabs is mainly centred on the amphibian’s eggs and tadpoles (Pyke et al., 2013), even though there are some reports of occasional predation on juveniles and adults (McCormick & Polis, 1982; Toledo, 2005; Hirschmann & Hödl, 2006; Gutsche & Elepfandt, 2007; Caldart et al., 2011; Andrade et al., 2012; Pyke et al., 2013). 6) Corresponding author; e-mail: [email protected] © Koninklijke Brill NV, Leiden, 2014 DOI:10.1163/15685403-00003331 NOTES AND NEWS 891 In Madagascar more than 300 species of frogs can be observed, 99% of which are endemic (Glaw & Vences, 2007; Vieites et al., 2009). Boophis Tschudi, 1838 is a genus of nocturnal arboreal frogs, characterised by their large bright eyes. The genus comprises more than 70 species and is the most speciose genus of amphibians in Madagascar (Köhler et al., 2011). Boophis rufioculis Glaw & Vences, 1997 is a species found in the eastern rainforest zone of Madagascar and associated with small streams (Glaw & Vences, 2007). Despite the wide distribution and great diversity of freshwater crabs, their role in the ecology of freshwaters is still poorly understood (Dobson, 2004). Here we describe a predation attempt of an individual freshwater crab (Hydrothelphusa sp.) on a Malagasy treefrog that took place in Betampona Strict Nature Reserve in Eastern Madagascar. This is the first report of a freshwater crab feeding on an adult amphibian in Madagascar. Betampona Strict Nature Reserve is a 2228 ha fragment of the once continuous lowland rainforest and considered to be a hotspot of biodiversity (both fauna and flora) (Rosa et al., 2012). At 10:30 am on 2 November 2007, on top of a small rock in the middle of a stream at Sahabefoza, Betampona (17°5445.5S 49°1227.9E, 356 m a.s.l.), a freshwater crab of the genus Hydrothelphusa was observed to feed on an adult treefrog, B. rufioculis (fig. 1). The crab held the frog by one of his hindlimbs, and one foot was already consumed when the observation began. The frog was still alive and trying to escape, whilst the crab pulled it towards the water. The outcome was not observed but it does not necessarily imply the death of the prey, as other similarly-mutilated individuals of B. rufioculis were discovered at later times, which could imply prey have the ability to escape encounters with predatory freshwater crabs (such as an adult giant treefrog, Platypelis cf. grandis (Boulenger, 1889); fig. 2). Direct observations of freshwater crabs catching and consuming adult frogs have never been recorded before in Madagascar. However, Glaw & Vences (2007) did observe very low numbers of the tree-hole breeding frog (Mantella laevigata Methuen & Hewitt, 1913) near sea level on the Malagasy offshore islet Nosy Mangabe; here, tree-holes were occupied by marine crabs (Labuanium gracilipes (H. Milne Edwards, in Jacquinot & Lucas, 1854)) which might be frog and tadole predators. Also, the fact that some stream anurans in Madagascar do very rarely dive but often try to leave the water with a few jumps, might be related to potential predation by freshwater crustaceans (Glaw & Vences, 2007). Similarly, reports of freshwater crabs preying on adult amphibians in continental Africa are rare, although Gutsche & Elepfandt (2007) documented a case of Potamonautus sp. predating on Xenopus laevis (Daudin, 1802) in South Africa. It is interesting to note that the observation of Hydrothelphusa predating on an the adult frog took place during the day, despite the fact that freshwater crabs are.