Onchidoris Blainville 1816

Genus Onchidoris Blainville, 1816

Onchidoris: Blainville, 1816: 96

Synonyms:

Ancylodoris Dybowski, 1900 Atalodoris Iredale & O'Donoghue, 1923 Lamellidoris Alder & Hancock, 1855 Oicodespina Gistl, 1848

Onchidiorus Fèrussac, 1822

Onchidora Cuvier, 1830

Onchiodora Desmarest, 1858 Oncidoris Herrmannsen, 1847 Onchidorus Blainville, 1816 Oncidiodoris Gray, 1847

Oncodoris Agassiz 1846

Proctaporia Mörch, 1857 Villiersia Orbigny, 1837

Type species: Onchidorus leachii Blainville, 1816, by monotypy

Diagnosis. The notum is covered with well-defined spiculose tubercles of various shapes in most species. The integument contains a dense network of spicules. The rhinophores are lamellate. The rhinophoral pockets have poorly defined contractile smooth sheaths adjoined by several tubercles. The contractile gills are unipinnate, inserted separately in an almost complete circle around the anus. A common gill cavity or separated gill pits are completely absent. The oral veil is well defined, semi-circular. The foot is broad, not bilobed anteriorly, slightly narrowed posteriorly. The labial cuticle contains weakly defined polygonal elements. The buccal pump is large, prominent, on a narrow stalk, fully banded medially by a broad peripheral muscle. The salivary glands are short. The radula formula is 1–0.1.0–1.1.0–1 (but two outer laterals were reported from O. muricata by Thompson & Brown (1984)). The central teeth are small and rectangular; absent in most species. The first lateral tooth posesses a variably beak-shaped cusp, bearing small denticles in most species. The outer lateral teeth are squarish or elongate and usually posess a posterior or anterior denticle. The stomach is relatively small, a caecum is absent. The male part of the reproductive system shows a single short or looped prostate, and a long ejaculatory duct within a muscular sheath. The penis is not armed. The post-ampullar gonoduct bifurcates into a vas deferens and a proximal oviduct, which connects to the vagina. The combined distal oviduct and uterine duct starts separately from the vaginal duct, close to the external genital opening. The bursa copulatrix is small and rounded. The seminal receptacle is distinct but always buried within nidamental glands near to the base of the bursa.

The genus includes 15 valid species (one of them is described in the present paper, Table 3). The North Atlantic and the Mediterranean Sea is the center of the genus diversity. Most of the Atlantic species of the genus still are poorly known anatomically. Some species, e.g. O. tridactila Ortea & Ballesteros, 1982 were described only from few specimens and their deliniation from for instance O. neapolitana (Delle Chiaje, 1841) is not completely satisfactory; both O. neapolitana and O. tridactila share very similar first lateral teeh with a strongly folded flange.