Diacavolinia vanutrechti Van der Spoel, Bleeker and Kobayasi, 1993 forma meisenheimeri Van der Spoel, Bleeker and Kobayasi, 1993
Overview
This is a large uncoiled thecosomatous pteropod, 0.8 cm long. It has a flat dorsal side with moderately developed ribs. The ventral side is vaulted. The caudal spine is absent and a caudal spine mark is not left as the ventral and dorsal sides grow together. The lateral spines are small but pronounced, usually hook-shaped. Shell sculpture consists of growth lines and faint transverse striation. The dorsal lip has a small notch, a gutter and sometimes a small constriction, usually there is no inner hump. Micro-zooplankton and phytoplankton are its food and it is a mucus feeder. It lives in Pacific Ocean at shallow depths (Diacavolinia v. meisenheimeri 2).
Taxonomic Description
The hyaline colourless shell is not triangular. The dorsal lip usually has a notch in the slender rostrum. There is sometimes a constriction and a gutter is present. The ventral lip is moderately sized and shows a clear median depression. The lateral spines are strongly bent and hook-shaped; the gutter corners are small. The 21 thin ventral ribs are slightly comb-shaped. The lateral lines are convex and the flanks are moderately developed. The dorsal side is somewhat flattened, with a moderate central rib, latero-dorsal ribs and lock ribs. The lock area is small, having a small main tubercle on a ridge, a small lunar and very small minor tubercle; the link is also small. A second lock mechanism midway between the lateral spine and the normal lock area is present. The growth lines are typical. A hump is absent. The protoconch II area does project moderately with a moderate caudal joint. In the holotype it is 1.12 mm; the caudal fold, 1.20 mm long, is slightly moon-shaped and the left and right fold form an angle. There are no lip flaps; weak lip bellies and moderate lip shoulders are present. The aperture is wide. In the holotype the lip angle is 152°, the lock angle is 75°, and the side angle is 83° (Diacavolinia v. meisenheimeri). The holotype has a shell length of 6.80 mm, the width is 4.16 mm.
The shell length ranges from 7.76 to 4.32 and width from 4.96 to 2.96.
Juveniles
A special description for this forma is not available, see Diacavolinia longirostris.
Reproduction
This species is a protandric hermaphrodite.
Ecology
This species is phytophagous.
Distribution
Diacavolinia vanutrechti forma meisenheimeri is found so far in the open ocean of the Central Pacific Ocean, see the Diacavolinia v. meisenheimeri map.
Types
Diacavolinia vanutrechti forma meisenheimeri Van der Spoel, Bleeker and Kobayasi, 1993: 136, fig. 8.
The holotype (ZMUC. gas 155) is preserved in the ZMUC.
Type locality: 18°53'S 163°02.5'W, 0-300 m depth, CDAE, Stat. 3580 iii.
Etymology: The name is given in honour of Dr. J. Meisenheimer who in, 1905, was the first to give a full overview of the distribution of pteropods.