Green finger sponge

Description:

Sponge with upright or sprawling cylindrical branches that occasionally divide. The branches are about 4 cm (1.6 in) in diameter and can grow to 50 cm (20 in) in length. Young individuals and some large specimens have an encrusting habit. They grow over the surface of a rock in a layer a few mm thick with occasional short chimney-like outgrowths. Other individuals have a number of vertical tubes, each with a large opening called an osculum at the end. These variations in growth habit led to the belief that several different species of sponge were involved. However, specimens growing in reef caves often have an encrusting base with a central, finger-like cluster of branches, so it is now believed that the different forms are a single species, perhaps differing in structure because of different environmental conditions. In the branched form, the osculi are found on the upper side of the branches and may be slightly raised above the surrounding tissue. The consistency of the sponge is soft but resilient, and when squeezed, it exudes a purple fluid. The general colour of the sponge is purplish black but there is often a layer of bright green cells on the epidermis. These have dendritic patterns on the surface and cover sub-surface canals which lead to the osculi.

Habitat:

Buddy's Reef, Bonaire.