Laginiopsis trilobata Pruvot-Fol, 1922
[dubious species]
Overview
This is a naked pelagic snail, up to about 1.5 cm long, characterised by the three lobes on top of the proboscis. Only one specimen was ever recorded from the N-Atlantic. In 1954 Pruvot-Fol gave no account of this species of which only one specimen has ever been recorded, so one may conclude that it was a dubious species (Laginiopsis trilobata).
Taxonomic Description
Head and body separated by a clear incision. No ciliary rings present on the body. The long "proboscis" has two large and one small terminal lobe. The median footlobe is short and it shows a distinct median tubercle. The lateral footlobes are normally developed. The wings are long, undulated and triangular. The wings slightly resemble those of Cephalobrachia. The anterior tentacles are large, triangular, and like the footparts resembling those of Thalassopterus. Body shape is rounded. Contractility of wings, proboscis and footparts is probably small or absent as musculature is rare. The proboscis is the most remarkable structure in the animal. It is terminated by three large round lobes with circular and longitudinal muscles. In between the lobes the mouth is found dorsally, with the two buccal ganglia and buccal commissure, the connections run posteriorly downwards along the oesophagus. Posterior to the three lobes and slightly ventral two, small, conical tentacles are found. The real anterior tentacles are found on the head at both sides of the proboscis base. The dorsal tentacles are found in the typical position. Buccal organs such as jaws and radula are absent. The proboscis is to all probability not a real proboscis and the three lobes may be homologous with buccal cones as concluded from their inner organisation.
Total length 14 mm.
Structure and Morphology
Though the buccal organs are absent, the buccal ganglia are well developed with connections to the cerebral ganglia which, like the pedal ganglia, show no peculiar structures. The pleuro-visceral chain differs from that in other Gymnosomata in being less concentrated. There are five, instead of four ganglia, which renders the total number of ganglia to nine. The digestive tube is very aberrant. The oesophagus enlarges when entering the head parts. These parts form a large glandular sac in which the liver-gland debouches. Intestine and anus are normally present.
Juveniles
A special description is not available.
Reproduction
The sexual organs are of the normal type. It is thought to be a protandric hermaphrodite.
Ecology
The species is thought to be carnivorous.
Distribution
It is only known from its type locality in the N-Atlantic. See the Laginiopsis trilobata map.
Types
Laginiopsis trilobata Pruvot-Fol, 1922: 696. This species was collected only once, and described from an undamaged and uncontracted animal.
Holotype: MOM (alcohol collection) dissected.
Type locality: 37°13'N 19°10'W. Coll.: Expedition of the "Prince Alice" stat. 1905.