Flabellina ischitana

The name ischitana means from Ischia, the island from where this nudibranch was first named.^[3]

This species is found in Mediterranean waters around Spain in such locations as Costa Brava,^[4] and in the Tyrrhenian Sea, especially around Ischia (hence the species Latin name).^[3][5][6]

Flabellina ischitana usually can be found in shallow water, but it can also reach depths of 35 m.^[3]

This species can grow to a length of approximately 4 cm and is mostly purple-violet in colour. It has opaque white-tipped certa, rhinophores, and oral tentacles. The rhinophores are annulate.^[7] Due to the somewhat transparent skin of the ceras, the branches of the digestive gland are visible, and appear as red-orange.^{[3][5][6][8][9][10]}

Flabellina ischitana is often confused with Flabellina affinis, but can be distinguished as follows:^[3][6]

• Flabellina ischitana: the ceratal surface has no purple-violet colouration and is translucent;
• Flabellina affinis: the digestive gland is not visible as the area beneath the subapical white ring is opaque;

Flabellina ischitana is also similar to Edmundsella pedata, but they can be distinguished on the basis of their rhinophores:^[7]

• Paraflabellina ischitana has annulate rhinophores.
• Edmundsella pedata has smooth rhinophores.

This nudibranch likely eats hydroids of the genus Eudendrium (Eudendrium racemosum and Eudendrium glomeratum) as its main food source.^[3][5][8]

Like other nudibranchs, this species is hermaphrodite. Mating occurs in late spring.^[6] The egg case is whitish or reddish,^[8] with thousands of eggs of about 70 microns. The nudibranch places the egg case on the branches of hydrozoa.^[6]

• Egidio Trainito, Nudibranchi del Mediterraneo. Guida al riconoscimento dei molluschi opistobranchi, 2005ª ed., Milano, Il Castello, 2005, ISBN 88-8039-438-X.
• Gary R. McDonald, University of California Santa Cruz - Nudibranch Systematic Index, University of California Santa Cruz - Institute of Marine Sciences