Atlanta turriculata forma turriculata d'Orbigny, 1836
Overview
This is a small sized, dextrally shelled, pelagic snail, 0.3 cm in diameter with large eyes and a single swimming fin. There are 5.5 whorls. The buff or rosy shell is strongly flattened and keeled. The spire is very high and straight. The spire of the operculum is relatively small with two spiral lines of dots. It is a carnivore predating on relatively large zooplankton. This species occurs in the warm waters of the Indo-Pacific Ocean (Atlanta t. turriculata lateral, Atlanta t. turriculata oral view).
Taxonomic Description
The shell is buff or rosy, transparent and has up to 5.5 whorls. The spire is very high and shows an apical angle of about 40°(Atlanta t. turriculata lat). About 7 spiral lines form the sculpture of the protoconch II; the uppermost of these lines is keel-shaped. The high keel slightly penetrates between body whorl and spire (Atlanta t. turriculata 2). The whorl formula varies between 1 : 0.24 : 0.11 and 1 : 0.28 : 0.16. The eyes (type A) are rounded, cuboid in general shape and the retinal windows are very small. The operculum (type A) is rounded, the axial margin is round or obtuse; the gyre is relatively large, but the central part is relatively small and situated in the upper half of the gyre. The operculum is thick (Atlanta t. turriculata oper., Atlanta t. turriculata operc, Atlanta t. turriculata opercul, Atlanta t. turriculata op+sp). Two spiral rows of small dots or spines are found around the nucleus.
Shell diameter up to 3 mm.
Juveniles
The juveniles have a small dextrally coiled shell. The Atlanta t. turriculata juv. has a relatively high coiled shell with six velar lobes each with a dark chromatophore at the tip. The Atlanta t. turriculata veliger quickly become high coiled and than has the undulating spiral lines. The Atlanta t. turriculata juvenile when living shows the spire as a red nucleus. The Atlanta t. turriculata protoconch I is smooth, the protoconch II has spiral lines and the teleoconch has many spiral lines of small dots in young specimens.
Reproduction
In this species the sexes are separate.
Ecology
This is a carnivorous and epipelagic species.
Distribution
This species occurs in the warmer waters of the Indo-Pacific, see the Atlanta t. turriculata map.
Types
Atlanta turriculata d'Orbigny 1836: 173, pl. 20, figs. 5-11.
Types not found in MHNP, or BMNH were they should be present (cf. Gray, 1854).