Peraclis depressa (non Vayssiére, 1913) Meisenheimer, 1906a

Overview

This is a pelagic snail with a left coiled shell, 0.3 cm high; it has 3 whorls and a deep suture without radial crests. The spire is depressed. A short keel ends in a distinct aperture tooth. The aperture is wide, the base of the aperture is pointed towards the keeled rostrum. The shell surface shows a regular structure of spiral lines which sometimes constitutes a reticulate pattern. The wings are fused into a swimming plate. This species lives usually at great depths in the Atlantic Ocean (Peraclis depressa).

Taxonomic Description

The shell is only slightly elongate and composed of three whorls with a deep suture. The spire is depressed, with whorls quickly increasing in size. A tooth-like protrusion is visible in the inner angle of the upper aperture border which is turned upwards and lies close to the apex. The aperture tooth has a keel which runs only over a short distance, along the upper whorl. Radial striae between the suture and keel are lacking. Outer aperture border regularly rounded. Columella provided with a very strong keel which continues into the rostrum; the columellar membrane is relatively well developed, but not broad. The umbilicus is clearly visible and wide. The rostrum is invisible in apical view. The shell surface has a regular structure of spiral lines which sometimes constitutes a reticulate pattern. The colour of the shell is white, only large specimens have a yellowish apex, the keel is horny to yellow. The operculum, with five whorls, has no radial striae.
Shell measurements of the type specimen: height 3.0 mm, maximum diameter 2.5 mm.

Juveniles

The juveniles have a small left coiled shell. A special description is not available.

Reproduction

This species is a protandric hermaphrodite.

Ecology

This species is phytophagous and mesopelagic.

Distribution

This species is typical for the E-Atlantic occurring in the eastern and southern basins, see the Peraclis depressa map. There is no proof of its occurrence in equatorial currents.

Types

Peraclis depressa Meisenheimer, 1906: 125, pl. 5, fig. 12.
Syntypes: HMEB S6725a, 3 spec., HMEB 56725b, 1 spec., HMEB 56725C, 1 spec. (alcohol collection) (Dr. Kilias in let.).
Type locality.: 11°S 19°W; 32°5'S 8°30'W ; 21°N 32°W. Coll.: CDSE stat. 11-X-I901; stat. S-XI-1901; stat. 13-X-I903.

Kingdom Animalia
Phylum Mollusca
Class Gastropoda
Subclass Euthyneura
Order Thecosomata
Suborder Pseudothecosomata
Family Peraclididae
Genus Peraclis
Species Peraclis depressa

Status in World Register of Marine Species

Not included in WoRMS database

Scientific synonyms and common names

Peraclis depressa (non Vayssiére, 1913) Meisenheimer, 1906a

Synonyms

Peraclis depressa n. sp. (non Vayssiére, 1913) Meisenheimer, 1906a: 125
Peracle depressa Tesch, 1913c: 76

Haagensen, D. A., 1976 Caribbean zooplankton. Part II. Thecosomata. Off. Nav. Res. Dept. of the Navy. U. S. Govt. Print Off. Washington D. C.: 551-712.

Meisenheimer, J., 1906a. Die Pteropoden der deutschen Südpolar-Expedition 1901-1903. Deutsch. Südpol.-Exp. 1901-1903, 9 (Zool.) 1(2): 92-153, pls 5-7.

Starobogatov, J. I., 1971. Ordo Thecosomata; ordo Gymnosomata; ordo Heteropoda. In: Polevoy Zool. Inst. Akad. Moscou. opredeliteli planktona (without page or figure numbers, not bound, mimiographed). [in Russsian]

Tesch, J. J., 1913c. Mollusca, Pteropoda. In: F. E. Schulze. Das Tierreich. Eine Zusammenstellung und Kennzeichnung der rezenten Tierformen 36. Berlin (Friedberger and Sohn): i-xvi, 1-154, 108 figs.

Spoel, S. van der and Heyman, R. P., 1983. A comparative atlas of zooplankton. Biological patterns in the oceans. Bunge, Utrecht; Springer Verl., Berlin: 1-186.

Spoel, S. van der, 1976c. Pseudothecosomata, Gymnosomata and Heteropoda. Bohn, Scheltema & Holkema, Utrecht. 484 pp. 246 figs.

Vayssiére, A., 1915a. Mollusques euptéropodes (ptéropodes thécosomes) provenant des campagnes des yachts Hirondelle et Princesse-Alice (1885-1913). Résul. Camp. Scient. accompl. yacht par Albert Ier, prince souverain de Monaco 47: 1-226, 14 pls.

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