Paraclione longicaudata (Souleyet, 1852b)
Overview
This is a naked pelagic snail, up to 1 cm long with a slender, mainly transparent body, the visceral mass is seen through the body wall. The shape is slender and oval. The posterior footlobe is small or absent. There are two pairs of buccal cones. It hunts zooplankton as food. It lives in the Mediterranean, Atlantic and Indian Oceans in the upper water layers (Paraclione longicaudata drawing).
Taxonomic Description
Body small and very slender, pointed posteriorly. Chromatophores are found in the skin. The colour of the body is dark due to the black chromatophores which are found even on the wings. The posterior footlobe is absent in some specimens and when present small. The median tubercle is present in animals with and without posterior footlobes. Two pairs of buccal cones of the same type as in Clione, though larger, and beset with papillae, are present. A well developed anal field is present. The radula formula (Paraclione longicaudata radula) varies between 2-1-2 and 6-1-6 depending on age (specimens of 3 mm show the formula 3-1-3, those of 5 mm show a formula of 5-1-5 and those which are larger than 5 mm have a formula of 6-1-6). The median plate possesses one long spine on its free border and sometimes two reduced lateral ones. The jaw is reduced. The hook sacs are small, transparent, shallow depressions, each with less than 15 short curved hooks. Though a real lateral gill is absent; a transparent lacunar spot marks its place. A row of rugosities between the hook sacs represents the jaw. The penis, as described by Tesch, is composed of two compartments beset with small spines.
Body length up to 10 mm.
Morphology and Structure
The chromosome number is 32 (2N) (Thiriot-Quievreux, 1990)
Juveniles
A special description is not available.
Reproduction
This species is a protandric hermaphrodite.
Ecology
This species is a carnivore.
Distribution
It is the only widely spread species of the genus, occurring in the Atlantic and Mediterranean, near Madagascar, Arabian Sea and Indo-Malayan waters. No records are known in the Pacific Ocean. Most records are from near coastal localities. See the Paraclione longicaudata map.
Types
Clione longicaudata Souleyet, 1852: 286.
Holotype: MHNP (alcohol collection, dried) u.s.
Type locality: Atlantic Ocean. Coll.: Eydoux and Souleyet [1837].