Thliptodon antarcticus Meisenheimer, 1906a
Overview
This is a small naked pelagic snail, smaller than 0.4 cm long, with a mainly transparent body, the visceral mass is seen through the body wall. The wings are small, implanted laterally in the middle of the barrel-shaped body. It is a rather quick swimming carnivorous species. It is epipelagic and mesopelagic occurring in all oceans usually at great depth (Thliptodon antarcticus).
Taxonomic Description
Body transparent, rounded to oval, head and body parts are nearly of the same size. The three footlobes are usually fused. The median footlobe is short and pointed. No median foot tubercle present. The Thliptodon antarcticus radula formula is 3-1-1-1-3. The median plate is very slender, band-like and it shows a fine dentation, or an undulated anterior border. The intermediate plate distinctly differs from that in the other species in having a slightly curved spine at its tip. This spine bears a dentation resembling the dentation in median plates of Cephalobrachia. The three lateral plates are slender with straight margins; they are composed of a basal part and a top part attached to it with a free articulation. There are about 9 to 13 rows. The hook-sacs about 3 mm deep, each containing 30 to 50 hooks. Gullet bladders present. The penis shows an accessory sucker. It is possible that the specimens described by Meisenheimer (1906b) from the Antarctic seas indeed belong to a separate species, but in the original description nothing is found which distinguishes it from Thliptodon rotundatus.
Body length up to 4 mm.
Juveniles
A special description is not available.
Reproduction
This species is a protandric hermaphrodite.
Ecology
This species is a carnivore.
Distribution
This species is sympatric with Thliptodon diaphanus but is much more restricted in its distribution. So far it is known from the N-Atlantic, Indian Ocean, Antarctic waters and Tasman Sea. As it is also found in tropical waters, it does not seems to avoid cold waters as shown in the Thliptodon antarcticus map. Its occurrence in the Antarctic centre, however, needs special attention as this record is given by Meisenheimer and it concerns a sample from the Valdivia Expedition from which many tropical organisms were found at an extreme southern locality.
Types
Thliptodon antarcticus Meisenheimer, 1906: 144.
Holotype: HMEB 56752.c. (alcohol collection) u.s.
Type locality: Coll.: CDSE stat. 13-II-1902.