DISCODORIDIDAE

  Discodoris lilacina
(Gould, 1852)

Relevant Synonyms
Discodoris fragilis (Alder and Hancock, 1864)
Discodoris concinna (Alder and Hancock, 1864)
Discodoris concinniformis Bergh, 1888

Misidentification*

* Records of Discodoris fragilis (currently regarded as a synonym of D. lilacina) in NE Atlantic and Western Mediterranean belong in fact to the similar species D. confusa Ballesteros et al., 1985.

 drawing: Tuvia Kurz    

SHORT DESCRIPTION
Body flat, oval, with the posterior end of the foot covered by the notum. Mantle firm and rough to the touch. Dorsum covered by numerous, small conical tubercles, which are larger near the central area. Ventrally, the anterior border of the foot is grooved and notched. Head with a pair of small oral tentacles. Gill composed up to nine tripinnate brachial leaves, that can be retracted into a pocket beneath the mantle. Rhinophores lamellate.

color : animal pale greyish brown in overall appearance, with several rounded or oval dark brown spots of different sizes, being larger in the central region of the dorsum. Sometimes, two white patches in the dorsal midline, but obscured in heavily pigmented specimens. Along the innermost sides of the mantle margin, two lines of large, oval, black spots. The ventral side of the foot and mantle margin are covered with numerous brownish spots of various sizes.

common size : adult usually reach up to 60-70 mm in length.

DISTINGUISHING CHARACTERISTICS
D. lilacina belongs to a worldwide species-complex of doridaceans with a pattern of brown-spoted greyish coloration and tuberculated notum. All these species are quite similar in external appearance and they are indistinguishable if the internal anatomy is not studied.

BIOLOGY / ECOLOGY
Probably feeds on siliceous sponges. The spawn forms a wide and flat coiled egg ribbon, of 2-4 coils, up to 80 mm in diameter. This species is characterised by its ability to autonomise large sections of the mantle when disturbed.

habitat : intertidal or shallow water in the Indo-Pacific, usually under dead coral slabs. The specimen recorded in Israel was dredged 40 m deep; the specimen from Lebanon found in rocky bottom at 2-3 m depth.


1st Mediterranean record
Israel, 1977 [1974].


DISTRIBUTION
Worldwide: common in the tropical and subtropical Indo-Pacific, from the Red Sea to Hawaii. Mediterranean: recorded first in 1974 from Haifa Bay, Israel as Discodoris concinna Barash and Danin, 1977a); later in Lebanon (collected by G. Bitar and H. Zibrowius, Valdés and Templado, 2002).

ESTABLISHMENT SUCCESS
Very rare. Only two specimens found in the Levantine Sea.

speculated reasons for success :
-


MODE OF INTRODUCTION
Possibly via the Suez Canal.


IMPORTANCE TO HUMANS
None.


KEY REFERENCES

  • Barash A. and Danin Z., 1977a. Additions to the knowledge of Indo-Pacific Mollusca in the Mediterranean. Conchiglia, 13(5-6): 85-116.
  • Edmunds M.E., 1972. Opisthobranchiate Mollusca from the Seychelles, Tanzania, and the Congo, now in the Tervuren Museum. Revue de Zoologie et de Botanique Africaines, 85(1-2): 67-92.
  • Rudman W.B., 1999. Discodoris lilacina (Gould, 1852). Available via Sea Slug Forum http://www.seaslugforum.net/disclila.htm. Australian Museum, Sydney.

 

  • Valdés A. and Templado J., 2002. Indo-Pacific dorid nudibranchs collected in Lebanon (Mediterranean Sea). Iberus, 20(2): 23-30.

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Last update : December 2003

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