Of the 33 species that make up the genus Mariona, the nudibranch Marionia blainvillea is one of them. This species belongs to the phylum Mollusca, class Gastropoda, order Nudibranchia and family Tritoniidae. We will find specimens of this species mainly in the waters of the Mediterranean Sea, although it is also possible to observe it in the waters of the eastern Atlantic Ocean.
Juvenile specimens of this species are frequently observed among algae, corals and especially gorgonians, while adult specimens are usually hiding behind rocks and are less frequently observed. The body of Marionia blainvillea is elongated and rectangular in shape, with 10 to 12 branched appendages on both sides along its length. In the cephalic area, it has a structure formed by two lobes also branched in 6-7 prolongations. Above these cephalic lobes, and in the dorsal part of the body we find two arborescent rhinophores located at the top of a sheath. As for the coloration of this species, it is very variable throughout the development of the specimens. Juveniles are semitransparent whitish, with a white line bordering the dorsal part of the body. As these specimens grow, they change their body coloration to orange, reddish and various white spots.
The diet of Marionia blainvillea is based mainly on corals and gorgonians. It is common to observe juveniles of this species on species such as Eunicella cavolini, Eunicella singularis, Leptogorgia sarmentosa and Paramuricea clavata.
As for reproduction, like the vast majority of nudibranchs, Marionia blainvillea is a hermaphrodite species and therefore with the presence of male and female organs in the same specimen. Despite this, self-fertilization does not occur, but requires cross-fertilization between two specimens. After fertilization, the specimens lay in the form of a more or less cylindrical and semitransparent cord that is rolled into a spiral, and inside which we can observe tiny orange eggs, a clutch may contain between 70,000 and 80,000 eggs.
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