Cribrinopsis crassa

Cribrinopsis crassa or also known as fat anemone, is a species of cnidarian classified within the class Anthozoa, the order Actiniaria, and the family Actiniidae. It is an anemone found only in the Mediterranean Sea, on rocky substrates, where it clings in crevices and hollows of waters up to 50 meters deep.

Like all anemones, Cribrinopsis crassa has a basal disc that clings firmly to the seabed. From the basal disc, continues a part of the body that we call foot and that ends in the oral disc, in the center of which we find the oral opening, and surrounding it 96 tentacles arranged in 5 rows, short (rarely exceeding 5 cm), relatively thick, and with rounded apices. The maximum diameter of the specimens of this anemone, including the tentacles, is about 15 cm. The tentacles are grayish-green, with whitish bands present in some specimens, and with purple tips. They are usually located at the intersection between the rocky bottom and the sand, where it can bury a part of its body, leaving only the oral disc and its tentacles visible.

Cribrinopsis crassa is a solitary species, which preys on its prey mainly at night. To do so, it extends its tentacles, which are equipped with stinging cells (cnidoblasts) with harpoon-shaped capsules, capable of injecting a venom into its prey and immobilizing them. Prey includes zooplankton, small invertebrates and even small fish.

It is a species with separate sexes that, contrary to what we might expect, has its reproductive peak coinciding with the months in which the water is at lower temperatures. This is probably a peculiarity inherited from the Arctic origins of Cribrinopsis crassa. Individuals expel their gametes into the sea, where fertilization occurs and a swimming larva is formed, which will form part of the zooplankton for several weeks. It can also reproduce asexually by longitudinal fission of an individual.

It can be confused with Condylactis aurantiaca, although it is larger in diameter, similar in color but with thinner and longer tentacles. Its foot is not on a hard substrate and it can also sink in the sand, while Cribrinopsis crassa cannot.