Limapontia senestra (Quatrefages, 1844)

Author: Ian Smith on 9 March 2011

Synonyms:Cenia cocksii Alder & Hancock, 1848; Acteonia senestra Quatrefages, 1844; Cenia corrugata Alder & Hancock, 1848;

Description

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Body (excluding appendages)
Up to 6mm long. Smooth body with no tubercles, occasionally wrinkled. Black or brown, with greyish white or yellowish white median dorsal patch, line of dorso-lateral patches (may merge into band) and metapodium (tail). Markings may be clear or indistinct. Anus a short distance behind mid point of body (often difficult to see, except when defecating).
Head
Black or brown, with whitish rhinophores and eye patches. Rhinophores on adults are digitiform (Thomson). When animal extended, ridges may run forwards from the rhinophores to front of head (Eliot), or basal half of tentacle may extend forwards as a vane. Juveniles start to develop rhinophores when about 2mm long.
Foot
Sole translucent pale showing greenish ovotestis spheroids and darker digestive gland. No propodial tentacles or extensions, but anterior of foot slightly swollen.

Key identification features

Thin digitiform tentacles on head when 2mm long or larger, with or without anterior ridge or vane.
Pale metapodium.
Anus a short distance behind mid point of body.
Not in brackish water, except Fleet lagoon, Dorset.

Similar species

Limapontia depressa

No tentacles or rhinophoral crests (but yellow-brown variety may have sharp edges to recessed yellow eye-area, in front of and below eye).
Pale metapodium (tail) absent or negligible.
Dorsal anus close to posterior.
In brackish or fully marine salinity (though slow to adapt to change in salinity).

Limapontia capitata

Curved rhinophoral crest[1] above and in front of, but not below, each eye, no digitiform rhinophore.
Dorsal surface of metapodium[3] (tail), eye areas and rhinophoral crests[1] all whitish.
Anus a short distance behind mid point of body.
Not in brackish water.

Ecology

Lower-, mid-, and, in north, even upper-shore pools, on its foodplants; Cladophora spp. Hermaphrodite. Hypodermic impregnation; sharp style on end of penis punctures body wall of mate to enable injection of sperm. Spawn; February – September. Egg mass contains up to 40 ova; unusually small number, but the largest eggs (diameter 0.4mm) on record, for any opisthobranch. No veliger larval stage; miniature adults hatch from eggs. Only European opisthobranch, apart from Runcina coronata, to have no trace of a shell at any stage of its embryonic development (Thompson, 1976). In fully marine salinity, except for anomalous population in the Fleet (brackish lagoon), Dorset, S. England.

Distribution and status

Orkney and Norway to French Atlantic coast (See GBIF map)
Widespread around Britain and Ireland. Often scarcer than L. capitata (Gascoigne), but in some places, such as Orkney, L. senestra very much the commoner species. (See UK interactive distribution map, N.B.N.)

References and links

Eliot, C.N.E. 1910. A monograph of the British nudibranchiate mollusca. London, Ray Society. Supplementary Volume.
Gascoigne, T. 1975. A field guide to the British Limapontidae and Alderia modesta. J. Conch. Lond. 28: 359 – 364.
Rudman, W.B. Sea slug forum
Thompson, T.E. 1976. Biology of opisthobranch molluscs 1. London, Ray Society.
Current taxonomy; World Register of Marine Species

Photo:

Limapontia senestra. Length 4.3mm. Pale patches weakly developed on dorsum and subdorsally. Pale digitiform rhinophores, eye patches and metapodium (tail). Medial notch in tip of metapodium. Yellowish penis below right eye. Orkney. March 1975.

Photo:

Limapontia senestra. Illustration from Eliot, 1910. Ovotestis spheroids visible through translucent foot. Ridges indicated above eye patches. Colour of dorsal markings on old illustration has apparantly deteriorated to greenish; should be yellowish white.

Additional images

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Recorded UK distribution

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