Green Boring Sponge (Cliona viridis)

The Green Boring Sponge thrives in Gozo’s vibrant water, Divers can explore this fascinating species around Gozo’s renowned dive sites.

How to Identify a Green Boring Sponge

Cliona viridis, known as the Green Boring Sponge, varies in form based on the surface it grows on. In limestone and calcareous substrates, it excavates channels and chambers, while on other rock types, it encrusts the surface or forms massive structures. The osculi (exhalant openings) are yellowish-green or light brown with pale rims, and the ostioles (inhalant pores) are grouped on flat-topped, sieve-like protuberances which may be white, yellow, or brownish-green. The sponge’s color comes from the zooxanthellae in its tissues.

Where are Green Boring Sponges Found?

The Green Boring Sponge is found along the eastern coast of the Atlantic Ocean, the Indian Ocean, and the Mediterranean Sea, including around the Maltese Islands. It inhabits shallow waters down to about 367 meters, thriving in well-lit areas and semi-dark cave entrances.

Interesting Facts about Green Boring Sponges

The genus Cliona belongs to the family Clionaidae, order Clionaidae, class Demospongiae, phylum Porifera, and kingdom Animalia. This species is oviparous, with internal fertilization and external egg release. Larvae are planktonic with limited dispersal, settling on the seabed to develop into juvenile sponges in about two weeks. Zooxanthellae, present at metamorphosis, are likely transmitted during oocyte maturation.

Where Can I See Green Boring Sponges?

The Green Boring Sponge can be observed in the Mediterranean Sea around the Maltese Islands. A notable spot is at Reqqa Point on Gozo’s north coast, where the photo of this sponge was taken at a depth of 52m.