A new deep sea coralline sponge from Turks and Caicos Islands: Willardi caicosensis gen. et sp. nov.(Demospongiae: Hadromerida)

A new coralline sponge, Willardia caicosensis, assigned to the family Timeidae, is described from the deep fore reef off the Turks and Caicos islands, tropical western Atlantic ocean, where it is common at depths ranging from 100 to 119 m. Individuals vary up to 15-20 cm in width. The relatively thin aragonitic skeleton is covered with delicate pillars up to + 1 mm. The living tissue is restricted to the spaces between pillars and a thin sheet lying above the calcareous skeleton. Exhalant canals converge upon regularly spaced central oscules on the sponge surface. Siliceous spicules include tylostyles and amphiasters which are secondarily embedded in the aragonitic moiety of the skeleton. In addition, ultrastructural characters of the choanocytes, such as periflagellar sleeves are typical of the Order Hadromerida. Two types of cells with dense spherules are abundant in the mesohyl : spherulous cells packed with large heterogeneous inclusions, protruding at the surface of the sponge, and glycocytes with smaller ovoid corpuscles, mainly grouped along the basal calcareous skeleton. Rough collagen fibrils extend in tracts from the base of the sponge to the ectosome. Sparse bacteria are scattered in the mesohyl.