Hemimycale columella is a demosponge classified in the Poecilosclerida order and the Hyemdesmiidae family. The geographical distribution of this species includes both the waters of the Mediterranean Sea and the Atlantic Ocean, where it lives associated with hard substrates at depths between 10 and 60 meters. It is a species typical of rather poorly lit areas such as caves or large crevices, although occasionally it is also possible to observe it directly attached to various plants such as the rhizomes of Posidonia oceanica, or even on benthic animals.
Hemimycale columella is an encrusting sponge, which only rises about 1-2 cm above the surface it colonizes. However, it can occupy relatively large surfaces. Distributed throughout the body we find several holes more or less rounded and with a ridge protruding from the surface, giving the specimen the appearance of the craters on the surface of the moon, and because of this peculiarity its common name of crater sponge. These craters or siphonal orifices have an elevated edge of lighter color than the rest of the body which has a color between bright red, pink and orange. Soft and spongy to the touch, Hemimycale columella specimens have an internal skeleton formed by spicules of siliceous nature that intertwine with spongine fibers.
The feeding of Hemimycale columella, as expected of a sponge, is done by filtering the surrounding water, from which it captures the organic particles.
As for reproduction, Hemimycale columella is a hermaphrodite species that can reproduce both asexually by fragmentation and sexually during the months of April to October by releasing male gametes into the water column that are captured by other specimens to fertilize the eggs of the latter and give rise to a planktonic larva.
There is a possibility of confusing specimens of Hemimycale columella with Phorbas fictitus. To differentiate between them, it should be known that Phorbas fictitus does not have a light-colored circle around the craters or siphonal openings.
It should be noted that Hemimycale columella specimens often show the nudibranchs Geitodoris planata and Jorunna tomentosa, since both feed on sponge tissue.
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