Verongia and Tylodina

The Verongia (Verongia aerophoba) is a tubular sponge which we can find on some dive sites in Tenerife. Unlike the high sponges from the Caribbean, the sponges in the Canaries have a small size (10cm). Their numbers dramatically decrease under the pressure of the sea urchins Diadema but also because of the pollution.

The sponge is fixed on a support and filters water to get nutriments. Its surface is made up of small holes which suck the water and filter it, while directing it towards the centre of the body, from where it expulsed through the largest cavity. It does not have a muscle and thus can not move to seek food or to flee a polluted environment.

The Verongia appears green to us in diving, but when we use a light, it is brown orange as the photo showed. (Sorry, I begin with photoshop…).
It has a lethal weapon in the event of attack. It creates toxins “brominated isoxazoline alkaloids “, which dissuades the predator to eat them… However, there is a small gastropod (3cm) which is immunized against these toxins: the golden sponge snail Tylodine.






The Tylodine, (Tylodina perversa) lives, feeds from it and reproduces on this sponge. It has even learned how to accumulate these toxins for his personal use like immunizing its lay against possible predator or use its pigmentation for camouflage purpose. On this photograph, we can see 2 specimens of yellow Tylodine. Its life expectancy is from one to two years.






Here is a video on YouTube about the sponge filtration technique: