Tylodina perversa (Gmelin, 1791)
Class: Gastropoda Cuvier, 1797
Subclass: Heterobranchia J.E. Gray, 1840
Clade: Euthyneura Spengel, 1881
Clade: Umbraculida Odhner, 1939
Superfamily: Umbraculoidea Dall, 1889 (1827)
Family: Tylodinidae J.E. Gray, 1847
Genus: Tylodina Rafinesque, 1819
Species: Tylodina perversa (Gmelin, 1791) [Patella]
- Patella perversa Gmelin, 1791
- Tylodina atlantica Gray J.E., 1856
- Tylodina citrina Joannis, 1853
- Tylodina punctata Rafinesque, 1814
- Tylodina punctulata Rafinesque, 1814
- Tylodina punctulata Gray J.E., 1856
- Tylodina rafinesquii Philippi, 1836
- Tylodinella trinchesii Mazzarelli, 1897
The specimens of this species do not usually exceed 40 mm in length, although some animals have been cited as “giants” that measured up to 75 mm in length. The overall coloration of the animal (head, mantle, sides of the body, foot and rhinophores) is intense and uniform yellow. The body is high, the mantle is not completely developed so it is covered by the shell, which is slightly conical with the apex directed backwards, of pateliform type, like limpets, and covers almost all the animal’s dorsum when it is in rest, when the animal is moving both the head and foot stand out of the shell. Typically, the shell is not very calcified and usually it is covered by a flaky organic cover (periostracum). On the shell’s surface there are brownish radial grooves, which do not reach the apex, and concentric growth grooves. The head has a pair of long rhinophores, auriculate, and thicker on the base. The eyes are located just before the rhinophores. The head is extended forward in a cephalic veil from which two short triangular oral tentacles protrude. The gill, located on the right side of the animal, and protected by the shell, consists of about 10 bipinnate lamellae also colored yellow. The anal opening is located behind the base of the gill and the genital orifice can be seen just behind the right oral tentacle. The foot is very large, yellow and has radial grooves around its margin.
This curious opisthobranch is always associated with its food species, the sponge Aplysina aerophoba, from which also gets the body pigment, called “uranidine”. The animal is very cryptic, so it is not easy to locate it in the sponge. Since the sponge is in photophyllic environments, between 0 and 10-15 m deep, this is the depth at which the opisthobranch lives. These animals, while feeding on the surface of the sponge excavate a cavity on it, and often are found buried inside. It has been said that this species also feeds on the abundant cyanobacteria present in the tissues of the sponge. Experimental studies in the laboratory have found that it can feed also on sponge Aplysina cavernicola, a sponge that lives in caves and scyaphillic environments and that becomes dark upon exposure to air. T. perversa takes profit of the sponge several alkaloids to avoid predation, by expelling them in mucus when disturbed. Like a sponge, when the animals are exposed to air their yellow body becomes dark brown, almost black. The spawns of T. perversa are also yellow and also contain defensive alkaloids.
- Tylodina, derived from greek [tulos] = anything protruding or rising like a lump, knob or knot.
- Perversa, from latin [perversus] = reversely rotated, skewed, defective, wrong, that went wrong, probably referring to how the protoconch evolved (Bill Rudman) or to its excellent camouflage on the sponge
T. perversa is an eminently Mediterranean species that has been cited in some locations like the European Atlantic, the British Isles, Canary islands, St. Helens, Madeira, Azores and Cape Verde. In the Mediterranean it can be found all along the coasts, both in Eastern and Western basins, and in the Iberian Peninsula it is known in both the Atlantic and Mediterranean coast. Also cited in the Balearic islands. In the Catalan coast it can be seen in whatever habitat that allows the food sponge to live.
| : OBIS|
: GROC 2010-2011
: Enric Madrenas
: João Pedro Silva
: Bernard Picton
| : OPK|
: Manuel Ballesteros.
: M@re Nostrum
: Altres fonts
: Marine Regions
References for the species: Tylodina perversa
- Portugal: Calado and Urgorri (1999), Calado et al. (1999).
Gibraltar: García-Gómez et al. (1989).
Andalucía (Med.): Templado et al. (1993b), Ocaña et al. (2000), Peñas et al. (in press).
Levante: Templado, Talavera and Murillo (1983), Templado et al. (2002).
Catalunya: Vicente (1964), Ros (1975, 1978b), Ros & Altimira (1977), Altimira et al. (1981), Domènech et al. (2002), Becerro et al. (2003), M@re Nostrum [Cala Rovellada (Colera) 8/1998, Cap Ras (Llançà) 11/1998, Cap de Bol (El Port de la Selva) 8/1998, Illa Portaló (Cadaqués) 10/1998, Illa Mateua (L'Escala) 5/1998 y 9/1998, Cala Aiguafreda (Begur) 10/1997].
Baleares: Templado (1982a).
Canarias: McAndrew (1857), Odhner (1931, as T. citrina), Pruvot-Fol (1954), Nordsieck (1972), Pérez-Sánchez and Moreno (1990), Malaquias and Calado (1997), Ortea et al. (2001, 2003), Moro et al. (2003).
Madeira: Watson (1897, as T. citrina and T. rafinesque), Nobre (1937), Nordsieck and García-Talavera (1979), Wirtz (1999), Malaquias et al. (2001), Wirtz and Debelius (2003).
Azores: Dautzenberg (1889, as T. citrina), Wirtz (1998), Ávila et al. (1998), Ávila (2000), Malaquias (2001).
Sources: Cervera et al., 2004, Ballesteros, 2007, McDonald, 2006 and other sources.
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