Description Body smooth and elongated, up to 30mm long, limaciform, with the middle of the dorsum higher than the rest of the body, and a tappered posterior end. It is white in color, with generally elongated spots, reddish brown or orange, distributed more densely on the dorsum and scarcely on the flanks, but in the caudal region, which frequently has a spot (yellow in younger specimens) near the edge of the foot. It has two pairs of curved dorsal processes (which give the genus its name), usually tilted backwards and with the distal zone pigmented yellow to slightly more than half its total length (turning gradually to orange or reddish brown in adult specimens): The first pair is placed next to the rhinophores, while the second pair is placed next to the gills. The two oral tentacles, longer and thinner than the dorsal processes, are yellow throughout their length. The foot has two white tentacles in its anterior side, hook shaped and widened by their base. The rhinophores are perfoliated and have between 13 and 17 lamellae. The eyes are located right behind the rhinophores. It has three partially contractile tripinnate gills, arranged around the anus; the central gill leaf is larger (with up to 10 branches in larger specimens) and is located in a more anterior position than the lateral ones. The genital opening is located on the right side of the body, near the base of the extra-branchial process. The dark internal organs can be observed by transparency through the dorsum in the middle zone of the body.
Biology The specimens found in the Mediterranean are usually found on sponges such as Scalarispongia scalaris (Trainito & Doneddu, 2014). It is assumed that, as in the other species of Trapania, it feeds on entoprocts, which usually grow on the surface of the porifera. The spawn consists of a white scalloped ribbon adhered to the substrate by one of its edges. The coloration of Trapania orteai is similar to that of T. maculata, although the general shape of the spots and their number varies. T. maculata usually has a large spot on each flank (not described in British specimens), which does not exist in T. orteai. T. orteai‘s propodial tentacles are white (yellow in T. maculata) and the tentaculiform palaeal processes are significantly shorter than in T. maculata. Another similar species is T. aureopunctata, but the spots on T. orteai are larger and more abundant and have a stronger orange color. In addition, in T. aureopunctata the rhinophores, oral tentacles, gills and tail are white and there are one or two spots in lateral processes.
Trapania. The original generic name of this species was Drepania, proposed by Lafont in 1874. Pruvot-Fol in 1931 proposed changing the generic name to Trapania to disambiguate it from Drepania Hübner, 1816 (a group of lepidoptera). Madame Pruvot-Fol does not indicate the origin of the name, but there are two theories: the first would be dedicated to the city of Trapani, the province capital of western Sicily; the second would be inspired on the original generic name Drepania, derived from the Greek “Drepane” which means “sickle” and presumably refers to the shape of the appendages located on the sides of the rhinophores and gills in this genus. Pruvot Fol would have chosen the new name on the basis that it has the same meaning, but not the same sound and thus avoid confusion.
Orteai. Dedicated to Dr. Jesús Ortea Rato, Spanish malacologist of the Department of Zoology of the University of Oviedo, in recognition of his fruitful work in the study of the opisthobranchs.
Distribution To date it has only been observed on the Atlantic coast of the Iberian Peninsula, in the Algarve (Gavaia et al., 2003) and on the coasts of Cádiz and Huelva, including the Mediterranean area of Tarifa (Cervera & García Gómez , 1989). The Bay of Naples (Italy) hosts a good population in what would be the first clear reports for the Mediterranean Sea (Fabio Russo, pers.comm., Trainito & Doneddu, 2014). The observation of a solitary specimen in Bajo de Piles, in Cabo de Palos (Murcia) by Julio Martínez on 7/12/2017 would be the first confirmed report for the Iberian Mediterranean coasts, while the observation made on 26/10/2019 by Enric Pena of a single specimen 3 meters deep in Torredembarra would be the first for Catalan shores.
Known georeferenced records of the species: Trapania orteai
Cattaneo-Vietti, R., and T. E. Thompson. 1989. Mediterranean opisthobranch molluscs: a zoogeographic approach. Bollettino Malacologico (Pubblicazione Mensile Edita dalla Societa Italiana di Malacologia) 25(5-8):183-204.
Cattaneo-Vietti, R., R. Chemello, and R. Giannuzzi-Savelli. 1990. Atlante dei nudibranchi del Mediterraneo. La Conchiglia, Rome 264 pp, 14 pls. (104 clr. ill), line drawings.
Cervera, J. L., and J. C. García-Gómez. 1989. Dos nuevas especies de Trapania Pruvot-Fol, 1931 (Gastropoda: Nudibranchia) del sur de España. Bollettino Malacologico 24 (9-12): 189-204.
Cervera, J. L., J. Templado, J. C. García-Gómez, M. Ballesteros, J. Ortea, F. J. García, J. Ros, and A. A. Luque. 1988. Catálogo actualizado y comentado de los Opistobranquios (Mollusca, Gastropoda) de la Península Ibérica, Baleares y Canarias, con algunas referencias a Ceuta y la isla de Alborán. Iberus, supl. 1: 1-84.
Cervera, J. L., G. Calado, C. Gavaia, M. A. E. Malaquías, J. Templado, M. Ballesteros, J. C. García-Gómez, and C. Megina. 2004. An annotated and updated checklist of the opisthobranchs (Mollusca: Gastropoda) from Spain and Portugal (including islands and archipelagos). Boletín Instituto Español de Oceanografía, 20 (1-4): 1-111. L.
Cervera, J. L., J. C. García-Gómez, and C. Megina. 2000. A new species of Trapania Pruvot-Fol, 1931 from the Bay of Cadiz, with remarks on other Trapania species (Nudibranchia: Goniodorididae). Ophelia 52(1): 17-24.
Flanders Marine Institute. 2018. Maritime Boundaries Geodatabase: Territorial Seas. Maritime Boundaries Geodatabase. (http://www.marineregions.org/).
Garcia, F. J., and H. Bertsch. 2009. Diversity and distribution of the Gastropoda Opisthobranchia from the Atlantic Ocean: A global biogeographic approach. Scientia Marina. 73: 153–160.
García-Gómez, J. C.2002. Paradigmas de una fauna insólita; Los moluscos opistobranquios del estrecho de Gibraltar (Serie Ciencias) 20: 397 pp. Instituto de Estudios Gibraltareños. Algeciras, Cádiz, Spain.
Gavaia, C., M. A. E. Malaquias, G. Calado, and V. Urgorri. 2003. New records of Portuguese opisthobranch molluscs. Journal of Conchology 38 (2): 101-118.
Long, S. J.2006. Bibliography of Opisthobranchia 1554-2000. Bayside Books & Press, Tustin, CA, U.S.A. 672p.
Martínez-Chacón, M.2018. Nudibranquios de la isla de Tarifa, pequeñas joyas del estrecho de Gibraltar. Junta de Andalucía. Consejería de Medio Ambiente y Ordenación del Territorio.