Onchidoris bilamellata

Onchidoris bilamellata, common name the rough-mantled doris, is a species of sea slug, a dorid nudibranch, a shell-less marine gastropod mollusk in the family Onchidorididae.[1]

Onchidoris bilamellata
A live individual of Onchidoris bilamellata, head end towards the right
Scientific classification
Kingdom:
Animalia
Phylum:
Mollusca
Class:
Gastropoda
(unranked):
clade Heterobranchia
clade Euthyneura
clade Nudipleura
clade Nudibranchia
clade Euctenidiacea
clade Doridacea
Superfamily:
Onchidoridoidea
Family:
Onchidorididae
Genus:
Onchidoris
Species:
O. bilamellata
Binomial name
Onchidoris bilamellata
(Linnaeus, 1767)
Synonyms[1][2]
  • Doris bilamellata (Linnaeus, 1758)
  • Doris fusca Müller, 1776
  • Doris verrucosa Pennant, T., 1777
  • Onchidoris elfortiana Blainville, H.M.D. de, 1816
  • Doris leachii Blainville, H.M.D. de, 1816
  • Doris affinis Thompson, W., 1840
  • Doris lamellosa Johnston, G., 1842
  • Doris liturata Beck, H.H. in Möller, H.P.C., 1842
  • Doris echinata Lovén, S.L., 1846
  • Doris coronata Agassiz, L., 1850
  • Doris vulgaris Leach, W.E. in Gray, J.E., 1852
  • Onchidoris bilamellata liturata (f) Beck, H.H. in Bergh, L.S.R., 1878
  • Onchidoris bilamellata pacifica (f) Bergh, L.S.R., 1880
  • Ancylodoris baicalensis Dybowski, W., 1900

Distribution

This nudibranch has a wide distribution, mostly in colder intertidal waters to a depth of about 20 m. It has been found in the North Atlantic and the North Sea from Britain and France to the Norwegian Sea, Iceland and Greenland; along the North American coast as far south as Connecticut. It has also been recorded in the North Pacific in the Bering Sea, and from Alaska south to northern California.

These sea slugs sometimes occur in abundant numbers during breeding time, swarming with over 1,000 individuals per square metre, as has been observed on numerous occasions.[3][4][5][6] These swarms are all oriented in the same direction, determined by the flow of the tide. They follow each other at the same speed, forming columns, in different close-knitted rows.

Description
Onchidoris bilamellata with a rusty brown pattern

The maximum recorded body length is 38 mm.[7] They mostly show an abundant rusty brown pigment. But some individuals display a mixed pattern of colours, from a lighter brown colour to dark brown. Even fewer individuals are white, with brown color only in the rhinophores and the gills. A rare few are completely white, and yet they are not albinos, as their eyes are pigmented.

Onchidoris bilamellata has a broadly oval shape with its back covered with short, knobby papillae. Their antennae are comblike. The gills are arranged in two half rings on the back at the rear end and consist of 16 to 32 simple featherlike plumes.

The branchial ganglia are fused in Onchidoris bilamellata.[8]

Habitat

Minimum recorded depth is 0 m.[7] Maximum recorded depth is 55 m.[7]

Feeding habits

Onchidoris bilamellata feeds mainly on acorn barnacles in the genera Elminius and Balanus. It uses its rachidian tooth to chew away at the top plates of the barnacles and then sucks out the soft body.[9]

References
  1. Gofas, S. (2010). Onchidoris fusca (Müller O.F., 1776). In: Bouchet, P.; Gofas, S.; Rosenberg, G. (2010) World Marine Mollusca database. Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=140638 on 2010-11-05
  2. "Onchidoris bilamellata". Gastropods.com. Retrieved 5 November 2010.
  3. (in French) Pelseneer P. (1922). "Sur une habitude de Doris bilamellata". Annales de la Société royale zoologique de Belgique. 53: 28-32.
  4. Thompson T. E. (1984). "Migrations of Onchidoris bilamellata during tidal emersion: a refutation". Journal of Molluscan Studies. 50 (2): 123.
  5. Jim Anderson (2002). ".Onchidoris bilamellata - swarming in Scotland again". Sea Slug Forum. Retrieved 13 December 2009.
  6. "Onchidoris bilamellata aggregation in Maine, USA". Sea Slug Forum. Retrieved 17 December 2009.
  7. Welch J. J. (2010). "The “Island Rule” and Deep-Sea Gastropods: Re-Examining the Evidence". PLoS ONE 5(1): e8776. doi:10.1371/journal.pone.0008776.
  8. Alder J. & Hancock A. (October 1851). "Descriptions of two new species of nudibranchiate Mollusca, one of them forming the type of a new genus". Annals and Magazine of Natural History (series 2)8(46): 290-302, pls. 9-10.
  9. Naylor, Paul. 2005. Great British Marine Animals 2nd Edition, Deltor. ISBN 0-9522831-5-8
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