Notes: Also known from the Bahamas as Iotrochota atra Rützler, Maldonado, Piantoni and Riesgo, 2007. Deep purple to black, repent to erect, single or divided branches. Skin often with parrot green tinges; upon manipulation, the skin retracts; it stains the fingers deep purple, releasing mucus. Oscules aligned usually on top of branches, may be slightly elevated. Sometimes found as clusters of tubes with top oscules. Fully (thinly to thickly to massively) encrusting deep reef wall specimens with vivid green skin are tentatively assigned to this species instead of to I. arenosa owing to their dark color and lack of sand accumulation characteristic of the latter; also, because in mid-depth reef caves branching specimens may have wide encrusting bases; further detailed comparisons of spicules are pending. Rützler et al. (2007) decided that the material from The Bahamas, lacking birotulate microsclere spicules and style megasclere spicules, should be a different species which they named I. atra (Whitfield, 1901). But since its encrusting counterpart, I. arenosa, also lacks birotules and styles in the Bahamas, we feel it to be the result of a regional condition (of low silicon content?) that affects both species.
Author Reference: (Higgin, 1877)
Link: World Porifera Database