Tylodina rafinesquii

Tylodina rafinesquii Philippi, 1836

• Tylodinella trinchesii Mazzarelli, 1897

Description
The body is oval shaped, coloured opaque yellow, elevated and not as wide as the shell. The mantle is narrow, not exceeding the size of the external shell. The shell is patelliform, elevated and conical, with a shiny yellowish white surface that shows concentric growth lines. The apex of the shell extends slightly backwards and towards the left. The periostracum extends beyond the shell margin and shows no radial brown stripes. Rhinophores are long, cylindrical, folded longitudinally and thicker at their base. The eyes are located in front of the base of the rhinophores, inside an unpigmented area. There is a a pair of triangular oral tentacles. The gill has 14-16 branches on each side of the rachis and is located on right side of the body, protected by the shell. The foot is large and oval shaped like the body.

Biology
Specimens from the Mediterranean Sea and the Atlantic Ocean were found active both during day and night, always at shallow depths (0–4 m). The Atlantic Ocean specimens were collected on the sponge Aplysina aerophoba, while the ones from the Mediterranean were observed at the entrance of a cave and feeding on an Aplysina sponge, (but not the common species A. cavernicola nor A. aerophoba). It apparently feeds on Aplysina sponges, but it probably its main food are diatoms and foraminiferans growing into the sponge tissues, while taking some sponge products that give the animal its colour, identical to that of the sponge, for camouflage purposes. The spawn is a yellowish flat spiral with white eggs, smaller than those of T. perversa.

Etymology

• Rafinesquii. In honor to Contantine Samuel Rafinesque (1783-1840), polyglot and man of very varied talents who had a great interest in zoology and, especially, in malacology. In some of his works he described thousands of new species (he is the author of more than 6,700 taxa published between 1836 and 1838), but this propensity to find new species earned him severe criticism from the scientific community, which on the opposite also recognized him excellent natural history works.

Distribution
Reported in Madeira (Watson, 1897), the Mediterranean coast of France (as T. perversa by Göbbeler & Klussmann-Kolb, 2010, 2011); Italy (as Tylodinella trinchesii by Philippi, 1836; Mazzarelli, 1897), the NE Iberian Peninsula where it has been reported in Sant Feliu de Guíxols (Girona, Spain) by Fernández-Vilert et al. (2020) and Lanzarote, Canary Islands also by Fernández-Vilert et al. (2020).

Known georeferenced records of the species: Tylodina rafinesquii
Sources:
: OBIS : GROC 2010-2011 : Enric Madrenas : João Pedro Silva : Bernard Picton : GBIF.ORG	: OPK : VIMAR : Manuel Ballesteros. : M@re Nostrum : Altres fonts : Marine Regions

Similar species
Tylodina perversa has a depressed shell with a well-developed periostracum marked by brown radial bands, while T. rafinesquii has an elevated shell with an indistinct periostracum lacking brown radial stripes. These species also have differences in the radula. Tylodina duebenii is similar, but smaller in size and with the body coloured dark brownish purple, lives in deep water in the Mediterranean Sea and Eastern Atlantic (Warén & di Paco, 1996).

Abundance

Western Mediterranean:	★☆☆☆☆
Eastern Mediterranean:	☆☆☆☆☆
Atlantic Ocean:	★☆☆☆☆