Acanthodoris pilosa

Acanthodoris pilosa (Abildgaard in Müller, 1789)

• Acanthodoris citrina Verrill, 1879
• Acanthodoris ornata Verrill, 1879
• Acanthodoris pallida Bergh, 1905
• Acanthodoris pilosa var. albescens Bergh, 1880
• Acanthodoris pilosa var. pallida Bergh, 1905
• Acanthodoris pilosa var. purpurea Bergh, 1880
• Acanthodoris pilosa var. zealandiae Bergh, 1905
• Acanthodoris subquadrata (Alder & Hancock, 1845)
• Doris bifida Verrill, 1870
• Doris flemingi Forbes, 1838
• Doris flemingii Forbes, 1838
• Doris laevis Gray M.E., 1850
• Doris nigricans Fleming, 1820
• Doris pilosa Abildgaard in Müller, 1789 (original)
• Doris quadrangulata Jeffreys, 1869
• Doris rocinela Leach, 1852
• Doris similis Alder & Hancock, 1842
• Doris stellata Gmelin, 1791
• Doris sublaevis Thompson, 1840
• Doris subquadrata Alder & Hancock, 1845

Description
Body usually measures about 40mm long, with a maximum recorded length of 55mm. The mantle completely covers the body, shaped like a dome. Body color is variable, and could be white, pale grey, yellow, brown or black. The light colored specimens, specially the juveniles, may have darker spots or freckles, and their internal organs can be seen by transparency. The mantle is heavily spiculated with long, thin, radially arranged spicules that make it soft to touch. It is also covered of soft, tall, conical tubercles that give it the characteristic pilose look, but these tubercles could be contracted making identification more difficult. The foot is translucent white, occasionally with dark spots on the sole, the upper side is freckled as the mantle. The foot is both anteriorly and posteriorly rounded, internal organs can be seen by transparency in the centre, and it protrudes beyond the mantle when the animal moves. The head has narrow oral veil that forms two blunt, rounded oral tentacles at the sides. It has long rhinophores, usually bent back and outwards, with a smooth stem and 10-24 lamellae (numbers increase with specimen size) in its distal portion, and a nipple on the tip. They emerge from low pallial sheaths with crenulated rims and share the same colour of the mantle, but the lamellae that could be frequently yellowish and occasionally bright orange. There are nine relatively big tripinnate gills of the same colour of the mantle, often with white axis and some white on the leaves, that are located around the anus, in the back of the dorsum.

Biology
It is found from the surface down to 170 m depth. It usually feeds on encrusting polyzoans of the genus Alcyonidium, also found on Flustrellidra hispida. It reaches maturity at 8mm long (Miller, 1958), and the spawn is a convoluted ribbon of white eggs of 64-76 microns in diameter, forming a two turns spiral, attached to the substrate by one edge. The gill leaves and could be retracted independently under the mantle if the animal is disturbed.

Etymology

• Acanthodoris. From Greek “akantha”, thorn, spine + “Doris”, a sea nymph in Greek mythology, wife of Nereus, nymph of the waters and mother of Nereids.
• Pilosa. From Latin “pilosus”, hairy, shaggy, covered with hair.

Distribution
There are reports from the Arctic Ocean (Faeroes and Iceland) down to Morocco, it is common around the British Islands and in both sides of the North Sea. It is present in both Northern American shores, from Greenland to Virginia in the Atlantic, and from Alaska to Vancouver in the Pacific. Acanthodoris pilosa is considered “dubia” in the Mediterranean. Considered common in Palermo, Italy by Philippi (1836) (as Doris stellata Gmelin in Linnaeus, 1791 fide Thompson and Brown, 1984), in fact this species has only been reported in the Mediterranean by Forbes (1844) for the Aegean Sea (Cattaneo-Vietti & Chemello, 1987).

Known georeferenced records of the species: Acanthodoris pilosa

Sources:
OBIS GROC 2010-2011 Enric Madrenas João Pedro Silva Bernard Picton GBIF	OPK VIMAR Manuel Ballesteros M@re Nostrum Altres fonts Marine Regions

More pictures

Acanthodoris pilosa by Alexander Semenov

Acanthodoris pilosa by Alexander Semenov

Acanthodoris pilosa by Alexander Semenov

Acanthodoris pilosa by José Carlos García Gómez

Acanthodoris pilosa @ Forth stuary, Scotland 24-04-2016 by Matt Barnes

Acanthodoris pilosa @ Forth stuary, Scotland 24-04-2016 by Matt Barnes

Bibliography

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Bibliography based on the works by Steve Long, 2006. Bibliography of Opisthobranchia 1554-2000 and Gary McDonald, 2009. Bibliographia Nudibranchia, with later updates from other resources.

Further reading

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