Grey Leather Sponge

Overview

The grey leather sponge (Ircinia oros) is a massive, lobate sponge endemic to the Mediterranean Sea. It is commonly found in rocky environments, ranging from well-lit areas to the semi-dark entrances of marine caves.

Appearance

This sponge typically exhibits a spherical or lobed, massive form with a firm, flexible consistency that is notably difficult to tear. Its surface is covered in regularly distributed, small conical projections known as conules. The color ranges from light to dark grey, though it can vary based on light exposure. At the apex of its lobes, the sponge features distinct exhalant openings (oscula), which are often bordered by a darker membrane or ring.

Distribution & habitat

Ircinia oros is primarily found throughout the Mediterranean basin, including the Adriatic Sea and along the Tunisian coast. It thrives in diverse marine settings, including seagrass meadows and rocky substrates, often in areas with gentle currents.

Biology & behavior

As a filter feeder, this sponge draws in water through numerous small inhalant pores to capture microscopic organic particles, such as bacteria and unicellular algae, using specialized cells called choanocytes. It reproduces both sexually and asexually. In sexual reproduction, it releases gametes into the water column, leading to the development of free-swimming, ciliated larvae that eventually settle on a substrate to grow into new sponges.