Milne-Edwards, 1848
Description
— Larva. Veliger with left-coiled shell.
— Adult. Body variously detorted. The shell may be external, internal, reduced or lost. Ctenidia and mantle cavity usually reduced or lost. Operculum usually absent. Hermaphroditic; the reproductive organs are at the right-hand side of the body. Most marine, benthic species. The pelagic Order Thecosomata and the Order Gymnosomata are the pteropods, with and without shell respectively.
World-wide there are about 3000 species of opisthobranchs and 5% of these have been recorded from the shallow waters of the North Sea. Of these species, 30% are infaunal, the remainder epifaunal.
The opisthobranch subclass is polyphyletic; numerous evolutionary lines of early prosobranchs have achieved success by abandoning total reliance upon a rigid external shell. In fact, the 'sea-slug' facies have arisen many times in more or less independent lines of evolution. [After Thompson, 1988].
The following species of pelagic Opisthobranchia occur in the area:
Clione limacina
Clione limacina f. filifera
Clione limacina f. gracilis
Clione limacina f. limacina
Clione limacina f. minuta
Pneumodermopsis ciliata
Pneumodermopsis paucidens
Clio andreae
Clio cuspidata
Clio pyramidata
Styliola subula
Limacina lesueuri
Limacina retroversa
Limacina retroversa f. balea
Limacina retroversa f. retroversa
The following species of benthic Opisthobranchia occur in the area (De Kluijver et al., 2000a):
Acanthodoris pilosa
Acteon tornatilis
Adalaria proxima
Aegires punctilucens
Aeolidia papillosa
Aeolidiella glauca
Akera bullata
Alderia modesta
Aldisa zetlandica
Ancula gibbosa
Aplysia punctata
Archidoris pseudoargus
Armina loveni
Asperspina brambelli
Berthella plumula
Cadlina laevis
Calliopaea bellula
Colpodaspis pusillus
Corambe obscura
Coryphella browni
Coryphella gracilis
Coryphella lineata
Coryphella pedata
Coryphella pellucida
Coryphella verrucosa
Cuthona amoena
Cuthona caerulea
Cuthona concinna
Cuthona foliata
Cuthona gymnota
Cuthona nana
Cuthona pustulata
Cuthona rubescens
Cuthona viridis
Cylichna cylindracea
Dendronotus frondosus
Diaphana minuta
Doto coronata
Doto cuspidata
Doto dunnei
Doto fragilis
Doto millbayana
Doto pinnatifida
Doto tuberculata
Elysia viridis
Embletonia pulchra
Eubranchus cingulatus
Eubranchus doriae
Eubranchus exiguus
Eubranchus farrani
Eubranchus pallidus
Eubranchus tricolor
Eubranchus vittatus
Facelina bostoniensis
Facelina coronata
Favorinus blianus
Favorinus branchialis
Geitodoris planata
Goniodoris castanea
Goniodoris nodosa
Hermaea bifida
Hero formosa
Janolus cristatus
Janolus hyalinus
Jorunna tomentosa
Limacia clavigera
Limapontia capitata
Limapontia depressa
Limapontia senestra
Lomanotus genei
Lomanotus marmoratus
Microhedyle lactea
Okenia leachii
Okenia quadricornis
Onchidoris depressa
Onchidoris fusca
Onchidoris inconspicua
Onchidoris luteocincta
Onchidoris muricata
Onchidoris pusilla
Onchidoris sparsa
Philine angulata
Philine aperta
Philine catena
Philine pruinosa
Philine punctata
Philine quadrata
Philine scabra
Philinoglossa helgolandica
Placida dendritica
Pleurobranchus membranaceus
Polycera dubia
Polycera faeroensis
Polycera notha
Polycera quadrilineata
Retusa obtusa
Retusa truncatula
Retusa umbilicata
Rostanga rubra
Roxania utricula
Runcina coronata
Scaphander lignarius
Tenellia adspersa
Tergipes tergipes
Thecacera pennigera
Tritonia hombergi
Tritonia lineata
Tritonia plebeia
Volvulella acuminata