Results of the Rumphius Biohistorical Expedition to Ambon (1990). Part 8. Swimming crabs of Ambon (Crustacea: Decapoda: Portunidae)

During the Rumphius Biohistorical Expedition (RBE) to Ambon, 33 species of swimming crabs were collected in the littoral and upper sublittoral zone by hand on tidal flats, using SCUBA, and using a Holthuis dredge. Lissocarcinus arkati, L. laevis, Charybdis (C.) hellerii, C. (C.) orientalis, C. (C.) variegata, Portunus hastatoides, P. iranjae, P. longispinosus, P. stephensoni, T. chaptalii, T. cooperi, T. stephensoni are recorded at Ambon and in the Moluccas for the first time. The Portunus tenuipes complex is partly revised and P. rugosus sensu Stephenson (1961) is considered a synonym of P. tenuipes De Haan, 1835. A new species, P. pseudotenuipes occurring at Ambon, in the Philippines and off South-East Asia is described. The Ambon fauna includes 55 swimming crab species, while for the Moluccas fauna 70 species are known. This makes Ambon probably one of the best studied local portunid faunas in the Indo-Pacific. According to the RBE collection and literature data, several groups of species with certain habitat preferences are discussed. 1) Upper sublittoral dwellers. 2) Shore dwellers occur in the intertidal zone, mostly on tidal flats, and in the upper sublittoral. 3) Primarily rock, rubble and reefflat dwellers belonged mainly to the genus Thalamita. 4) Symbiotic species of Caphyra are associated with alcyonarians while Lissocarcinus are commensals of anthozoans and echinoderms. A new association was recorded for the first time for Lissocarcinus arkati (with sea urchins), and the association of L. laevis with ceriantharians was confirmed.