Yellow Cave Sponge

Overview

The Yellow Cave Sponge (Aplysina cavernicola) is a distinctive, light-yellow sponge endemic to the Mediterranean Sea. It is primarily found in shaded, low-light environments such as underwater caves, crevices, and beneath rocky overhangs.

Appearance

This sponge typically forms clumps that can reach up to 30 cm in diameter. It features a solid base that adheres to hard substrates, from which several finger-like projections emerge. These "fingers" usually measure 3 to 6 cm in height and about 2 cm in diameter, each topped with a slight depression containing a single, central osculum for water expulsion. The surface is textured with small, conical protrusions caused by the tips of internal horny fibers. Unlike many other sponges, it lacks mineral spicules, relying instead on a flexible mesh of spongin fibers for structural support.

Biology & Behavior

As a filter feeder, the Yellow Cave Sponge draws water through small pores at its base to extract bacteria, plankton, and organic debris. It is a hermaphroditic species that reproduces by releasing ciliated larvae, which eventually settle to grow into new colonies. To deter predators, the sponge accumulates high concentrations of brominated isoxazoline alkaloids in its tissues, making it unpalatable to many fish. In shallower waters, it is sometimes associated with the yellow sea slug Tylodina perversa, which may be found living among its finger-like projections.