A new species of Agelas from the Zanzibar Archipelago, western Indian Ocean (Porifera, Demospongiae).

Abstract
A new sponge species (Demospongiae: Agelasida: Agelasidae) is described from the eastern coast of Unguja
Island in the Zanzibar Archipelago. Agelas sansibarica sp. n. is compared to all other Agelas species
described so far. The new species differs from its congeners mainly in its three categories of verticillate
spicules (acanthostyles, acanthostrongyles, and acanthoxeas) and their sizes. Acanthostrongyles, well represented
in the spicular complement, are an exclusive trait of the new species widening the morphological
range of the genus. Summarizing on spicular complement and spicular morphotraits of 36 species
belonging to the genus Agelas: i) 32 species show only acanthostyles from Indo-Pacific (n = 14), Atlantic
(n = 17), and Mediterranean (n = 1); ii) three Indo-Pacific species show acanthostyles and acanthoxeas; iii)
one species A. sansibarica sp. n. from the western Indian Ocean is characterised by the unique trait of three
categories of verticillate spicules (acanthostyles, acanthostrongyles and acanthoxeas). A key for the Indo-
Pacific species is supplied together with short descriptions, illustrations, and geographic range; literature
on chemical bioprospecting of the genus Agelas is also provided.