Antedon mediterranea is a species of echinoderm belonging to those known as sea lilies (class Crinoidea). As its specific epithet indicates, this species is endemic to the Mediterranean Sea, where it can be found preferably on rocky bottoms, not very intensely illuminated and exposed to currents at depths of up to 400 meters, although they are more frequent between 10 and 40 meters deep. It is common to observe specimens of this species on gorgonians (Eunicella) or on seagrass meadows (Posidonia oceanica).
The body of Antedon mediterranea is formed by a cup-shaped disk in the center of which we find the mouth opening. Bordering the mouth are structures called pinnules that act as a comb to retain the food captured by the arms that project from the edge of the disk. The symmetry of Antedon mediterranea is typical of echinoderms, pentaradial symmetry with 5 arms, which bifurcate almost immediately after projecting from the edge of the disc, so that in appearance the specimens appear to have 10 arms. These arms, thin and elongated (8-9 cm long), also have pinnules all forming the same plane, which gives the arms the appearance of feathers. On the underside of the central disc are elongated appendages that the specimen uses to cling firmly to the substrate. The color is generally uniform throughout the body, with specimens that can be white, reddish, yellow, orange, red and occasionally any of these colors with white bands.
Through synchronized arm movements, Antedon mediterranea is able to swim through the water column, performing a medusoid movement that is very attractive to observe, resembling dancers dancing in the middle of the water column. They are also capable of self-amputating some of their arms as a strategy to mislead potential predators that focus on the amputated arm and not on the rest of the specimen. The specimen subsequently has the ability to completely regenerate the missing arm.
As for the feeding of Antedon mediterranea, it obtains its food by filtering the water column with its arm pinnules, to capture zooplankton and small crustaceans and molluscs. When the arms capture their prey, they retract and move towards the mouth where the pinnule comb transports their prey into the mouth to digest them.
Reproduction of Antedon mediterranea is sexual through the release of gonads during spring and/or summer, which will be fertilized externally and form planktonic larvae. After a process of metamorphosis, the larvae change from bilateral symmetry to form the juvenile specimen with pentaradial symmetry. The sexes in Antedon mediterranea are separated, i.e. it is a dioecious species, although there is no sexual dimorphism between males and females.
It is common to observe among the arms of Antedon mediterranea specimens of the shrimp Hippolyte prideauxiana. This shrimp is perfectly camouflaged among the arms of the sea lily, so we will have to pay close attention to observe them.
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