- Maximal shell size appears to vary geographically (=6 mm in the western tropical Pacific [Souleyet, 1852], 4 mm in the North Atlantic and Indian Oceans [Richter, 1986, 1974] and 2 mm off Hawaii [Seapy, 1990a,b] and eastern Australia [Newman, 1990]).
- Shell transparent with thin walls and keel
- Shell surface smooth, lacking raised sculpture on the spire whorls
- Spire very small, compact and somewhat elevated, consisting of about 2-1/2 whorls; spire whorls somewhat rounded and distinct from each other due to deep sutures (see fourth SEM image below)
- Keel tall, with a truncate leading edge (see first SEM image below)
Figure. Scanning electron micrographs of a 1.2 mm Atlanta lesueurii, viewed from the right side (upper left), the shell spire (upper right), the right side tilted (lower left), and the spire tilted (lower right). Scale bars = 0.5 mm (upper and lower left) and 100 µm (upper and lower right). © Roger R. Seapy
- Coloration: in Hawaiian waters juveniles lack body coloration (see second title illustration), but with growth the spire tissues take on pink (see first title illustration) to pinkish-violet (see photograph below) coloration
Figure. Specimen of a male Atlanta lesueurii retracted into its shell. Note the pinkish-violet coloration of the spire tissues. Shell diameter = 1.5 mm. © Roger R. Seapy
- Eyes type b, with a large lens (see first title illustration; also, in enlarged view the transverse slit in the distal pigmented tissue of the right eye can be discerned)
- Operculum type b; thin
- Radula type I; largest in the genus Atlanta
- Shape triangular
- Lateral teeth monocuspid (Richter, 1961)
- Number of tooth rows can exceed 100 in older adults (Richter and Seapy, 1999)
Diel vertical distribution patterns of Atlanta lesueurii (among the 13 species of heteropods in the study) were investigated off leeward Oahu, Hawaii in waters overlying a bottom depth of 2,000 m (between 9 and 11 km offthe coast) by Seapy (1990b). heteropods were collected during day and night periods using paired, opening-closing BONGO nets at 50-m depth intervals between the surface and 200 m and at 200-300 m and 300-400 m. Three or four replicated tows were taken in each depth interval. A. lesueurii was found to be the most abundant species, with a maximal density of 59 individuals per 1,000 m3 in a daytime 0-45 m depth interval. at a station ). The species ranged from the surface to 140 m during both day and night periods. There was an apparent partial populational migration from a depth interval of 45-90 m during the day to 0-45 m at night. However, high variability in densities between the replicated tows in each of the depth intervals resulted in statistically non-significant differences between day and night periods for each of the depth intervals.
In a subsequent study off leeward Oahu (Seapy, 2008), duplicate tows were taken with a MOCNESS mutiple, opening-closing net system during day and night periods at three stations located 1, 5 and 15 nm off the island in fall and spring sampling periods. Mean densities were computed (as numbers of individuals beneath 100 m2 of ocean surface) during day and night periods at each station. As in the 1990b study, A. lesueurii was the most abundant species in the fall, although it was a close second to A. plana in the spring. Comparisons were made using the nighttime density data to avoid issues such as daytime net avoidance and to include increased nighttime abundances resulting from possible nocturnal vertical migrator species. A. lesueurii was found to be most abundant at the offshore (15 nm) station during both seasons. Offshore to inshore abundance decreased most dramatically in the fall; from mean nighttime densities of 480 (15 nm) to 124 (5 nm) to 37 (1 nm) individuals beneath 100 m2 of ocean surface. At the 15 nm station the species ranged downward to the greatest depths; to the 120-160 m depth interval in the spring and to the 80-120 m depth interval in the fall. Clear evidence for nocturnal vertical migration was only seen in the spring at the 1-nm station (10-m depth intervai tows were taken in the upper 100 m at this shallow-water station). Highest abundances were recorded between 60 and 30 m during the day to 30 m to the surface at night.
No one has provided updates yet.