Idaliadoris depressa

Idaliadoris depressa
The nudibranch Idaliadoris depressa, Strangford Lough, Northern Ireland.
Scientific classification
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Gastropoda
Order:	Nudibranchia
Superfamily:	Onchidoridoidea
Family:	Onchidorididae
Genus:	Idaliadoris
Species:	I. depressa
Binomial name
Idaliadoris depressa (Alder & Hancock, 1842)
Synonyms [1] [2]
Atalodoris depressa(Alder & Hancock, 1842) superseded combination Doris depressaAlder & Hancock, 1842 Knoutsodonta depressa(Alder & Hancock, 1842) superseded combination Onchidoris depressa(Alder & Hancock, 1842)

Idaliadoris depressa is a species of sea slug, a dorid nudibranch, a shell-less marine gastropod mollusc in the family Onchidorididae. ^[1]

Description

(Original description) The body is notably depressed and transparent, with a pale sandy color and distinct spots of orange or reddish brown.

The cloak is covered in delicate, pointed papillae and contains strong, embedded spicules arranged in a transverse pattern across the back and diagonally on each side. The dorsal tentacles are a pale yellow.

The gill apparatus consists of ten to eleven very short, simple, and transparent white plumes, which are arranged in a horseshoe shape around the vent.

The foot is broad, with a truncated anterior end, and is a pale grayish-pink color. The veil above the mouth is large and semicircular. ^[3]

Distribution

This species was described from Whitley Bay, Northumberland, England. It is currently known from Norway south to the Atlantic coast of France and the Mediterranean Sea. ^[4] Reports from other parts of the world are doubtful and specimens from Brasil have been described as Knoutsodonta brasiliensis . ^[5]

References

1. MolluscaBase eds. (2025). MolluscaBase. Idaliadoris depressa (Alder & Hancock, 1842). Accessed through: World Register of Marine Species at: https://www.marinespecies.org/aphia.php?p=taxdetails&id=1618239 on 2025-09-09
2. Hallas J.M. & Gosliner T.M. (2015). Family matters: The first molecular phylogeny of the Onchidorididae Gray, 1827 (Mollusca, Gastropoda, Nudibranchia). Molecular Phylogenetics and Evolution. 88: 16-27, page(s): 25
3. Alder, J., & A. Hancock (1842) Descriptions of several new species of nudibranchous Mollusca found on the coast of Northumberland. Annals & Magazine of Natural History 9(55):31-36, page 32. This article incorporates text from this source, which is in the public domain .
4. Picton, B.E. & Morrow, C.C. (2015). Onchidoris depressa (Alder & Hancock, 1842). [In] Encyclopedia of Marine Life of Britain and Ireland. Accessed on 2016-1-15.
5. Rudman, W.B., 2003 (October 13) Onchidoris depressa (Alder & Hancock, 1842). [In] Sea Slug Forum. Australian Museum, Sydney.