A new species of Synalpheus Spence Bate, 1888 (Caridea: Alpheidae) from Aldabra

The material used in the present study was collected by the crew of Cousteau's vessel Calypso during the 1954 expedition to Aldabra, Seychelles. Synalpheus calypso sp. nov. is one of the few species in the Indo-West Pacific with a minor cheliped dactylus furnished with densely arranged tufts of distally-curved setae (known as gambarelloides setae). Amongst all these sponge-dweller species, the new species appears to be morphologically closest to S. spongicola Banner & Banner, 1981. Yet, S. calypso sp. nov. can be distinguished from the latter by the shape of the superior tooth of the basicerite, the dorsodistal tooth of the major cheliped merus, the shape of the posteroventral angle of the first pleuron in males, and the position of the dorsal spiniform setae on the telson. Other features differentiating the new species from the remaining Indo-West Pacific species with such a minor cheliped, include a subacute rostrum and orbital teeth reaching to the distal third and midlength of the first antennular article, respectively; a stylocerite overreaching the first antennular article; a well-developed scaphocerite blade; a major cheliped palm with a prominent up-turned dorsodistal tooth; and a complete uropodal diaeresis.