There are over 40 species and subspecies within the genus of Hypselodoris and none of which are listed on the IUCN Red List (1)(2). This seaslug, endemic to the Mediterranean , can grow up to 13cm long and has a light blue body with many yellow lines and spots. In some cases it can even appear to be entirely yellow in colour (3) (4). It is one of the largest nudibranchs within the Mediterranean, with a frill like body structure and a dominant gill tuft. Similar to Opisthobranchs, they have a large set of rhinophores at the head, with a set of gills at the end of the body (5). Juvenile species often have three lines along the dorsum, while the adults pattern is more complicated with numerous brown or entire lines. The lines often also reach the rhinophoral sheaths, forming a yellow circle around the edge of the rhinophoral sheath and then continuing forward (6). On the head, two labial tentacles are found, with a foot located below the dorsum. The foot is longer than the dorsum, with the exposed part forming a type of yellow spotted tail (3).
The majority of predation occurs during the planktonic larval state, with adults using camouflage and an array of toxins to ward of chemicals. The use of bright colour is suggested to be so that potential predators are warned off (7). If the Giant Doris becomes disturbed, it has been noted to retract both its rhiophores and branchial plumes into its plumes. It can take many minutes for the species to relax and expose them once more. If it is severly disturbed, it often forms a ball by bending its foot longitudinally, showing only the coloured parts (3).
Nudibranchs, such as H.picta, reproduce by exchanging packets of sperm from mature individual to another. In some case, communal mating groups can occur. After matine, both individuals produce egg masses, with some large individuals producing millions of eggs. The majority of nudibranchs begin their life as free swimming planktonic larvae. Once they have found a suitable food source, they settle and soon grow into adults. The life cycle of nudibranchs in general is very short, usually one or two months and in the majority of cases, no more than a year (7).
The Giant Doris can be found in the sublittoral zone, from the shallow waters all the way down to about 50m (4).
Nudibranchs of the genus Hypselodoris can be found throughout the Mediterranean and along the subtropical coasts of both the east and west sides of the Atlantic. Hypselodoris picta in particular can only be found within Mediterranean shores and apart from H. villafranca is the only species found on the eastern side of the Atlantic (4) (6).
As a carnivore, the Giant Doris has been noted to feed on sponges, encrusting hydroids and coral polyps (5). It tends to prefer the sponge of the genus Dysidea and Ircina (3) (4). The Giant Doris extracts metabolites from the sponges it consumes for defense, as they are toxic to most predators (3).
Not evaluated under the IUCN Redlist (2).
Description written by Kathryn Woodward (2009)
(1) ZipcodeZoo, 2009. Hypselodoris (genus). [Online] Available at: http://zipcodezoo.com/Key/Animalia/Hypselodoris_Genus.asp [Accessed 02 September 2009].
(2) IUCN, 2009. IUCN Red List. [Online] Available at: http://www.iucnredlist.org/search [Accessed 02 September 2009].
(3) Pontes, M., 2000. Nudibranchs: Hypselodoris picta. nudibranch NEWS.
(4) Wirtz, P. & Debelius, H., 2003. Mediterranean and Atlantic Invertebrate Guide. Hackenheim, Germany: ConchBooks.
(5) Wood, L., 2002. Sea Fishes and Invertebrates of the Mediterranean Sea. London: New Holland Publishers (UK) Ltd.
(6) Rudman, W.B., 2000. Hypselodoris picta (Schultz, 1836). [Online] Available at: http://www.seaslugforum.net/factsheet.cfm?base=hypspict [Accessed 02 September 2009].
(7) University, S.C., 2009. Order Nudibranchia (Nudibranchs). [Online] [Accessed 02 September 2009].