Halgerda formosa
Bergh, 1880

Order: NUDIBRANCHIA
Suborder: DORIDINA
Family: Dorididae

DISTRIBUTION

western Indian Ocean.

PHOTO

UPPER: Pereybere, Mauritius, Indian Ocean. Site: Le Grand Aquarium. Depth: 10m. Size: about 3cm. October 17, 2002 Photo: Marina Poddubetskaia
LOWER: original colour figures of Halgerda formosa published by Bergh (1888 - Pl 77, figs 10, 11).

This species was previously identified with H. punctata, a species described from Ceylon as 'whitish-grey, rather translucent with yellow papillae on mantle' and purple spots on foot and a few also on mantle' (Rudman, 1978 - Zanzibar, Gosliner, 1987 - South Africa).

However Fahey & Gosliner (1999) have concluded that the species illustrated here is H. formosa Bergh, 1880 and that H. punctata is a similarly coloured but distinct species. One external difference they note is that while H. formosa has distinct low ridges lined with yellow or orange, in H. punctata the ridges are indistinct and there are yellow tubercles. Another similarly coloured species is Halgerda toliara which can be distinguished as follows:
•H. formosa (Bergh, 1880) - yellow reticulate pattern - some black spotting around mantle skirt, and small whitish pustules near edge.
•H. toliara Fahey & Gosliner, 1999. - yellow reticulate pattern - no black spots on mantle, small yellow pustules near edge.

References:
• Fahey, S. & Gosliner, T.M. (1999) description of three new species of Halgerda from the western Indian ocean, with a redescription of Halgerda formosa, Bergh, 1880. Proceedings of the California Academy of Sciences, 51(8): 365-383.
• Fahey, S.J. & Gosliner, T.M. (2001) On the genus Halgerda (Nudibranchia: Halgerdidae) from Western Australia with descriptions of four new species. Bollettino Malacologico, 37(5-8): 55-76.
• Rudman, W.B. (1978) The dorid opisthobranch genera Halgerda and Sclerodoris from the Indo-West Pacific. Zoological Journal of the Linnean Society 62: 59-88.

Authorship details
Rudman, W.B., 1999 (November 18) Halgerda formosa Bergh, 1880. [In] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/factsheet/halgform

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