Diacavolinia bandaensis Van der Spoel, Bleeker and Kobayasi, 1993
Overview
This is a small uncoiled thecosomatous pteropod, 0.5 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 well developed. Shell sculpture consists of faint growth lines and an extremely faint transverse striation. The broad dorsal lip has a notch, no constriction but a gutter with inner hump is present. Micro-zooplankton and phytoplankton are its food and it is a mucus feeder. It lives in the Indo-Malayan waters at shallow depths (Diacavolinia bandaensis).
Taxonomic Description
The hyaline shell is clearly triangular and is an intense brown colour especially along the ventral lip rim, the joint, and the centre of dorsal and ventral sides.
The dorsal lip has no notch on the broad rostrum, and no constriction; a small gutter crossed by the strong inner hump is present (Diacavolinia bandaensis upper lip). The ventral lip is large and shows a clear median depression. Ventral and dorsal lip rims are thickened. The sometimes reduced lateral spines are not bent, lanceolate or sharp; the gutter corners are moderately developed. The 13 ventral ribs are line-shaped and composed of a series of tubercles. The lateral lines are convex; the flanks are clearly present. The dorsal side is flattened, with well-developed central and moderate latero-dorsal ribs; the lock ribs are weak. The lock area is well visible with a ridge-like main tubercle and a well-developed lunar tubercle; the minor tubercle is absent; the link is well developed. There is no secondary lock system. The growth lines are normal and on the upperside of the dorsal shell sculpture ribs are found. A strong hump is present with a strong inner hump. The protoconch II area only moderately projects outwards. In the holotype the rounded caudal joint is 1.12 mm; the moon-shaped caudal fold is 0.88 mm long. There are no lip flaps; moderate lip bellies and large lip shoulders are present. In the holotype the lip angle is 155°, the lock angle is 73°, and the side angle is 76°. The aperture is narrow.
The length ranges from 4.60 to 3.72 mm and the width from 4.24 to 3.00 mm.
Juveniles
A special description for this form is not available, see Diacavolinia longirostris.
Reproduction
This species is a protandric hermaphrodite.
Ecology
This species is phytophagous.
Distribution
Diacavolinia bandaensis is only found in the Banda Sea and may be endemic to this area, see the Diacavolinia bandaensis map.
Others
Species most related to the present one are Diacavolinia angulosa and Diacavolinia pacifica. but these are smaller than Diacavolinia bandaensis and already have a fully developed notch so that the present species can neither be a growth form of Diacavolinia angulosa nor of Diacavolinia pacifica. Diacavolinia bandaensis may sometimes resemble specimens of Diacavolinia grayi but in the present species the caudal joint is always near the level of the lateral spine tips, while in Diacavolinia grayi the joint distinctly projects posteriorly below that level.
Types
Diacavolinia bandaensis Van der Spoel, Bleeker and Kobayasi, 1993: 144, fig. 19.
Holotype (ZMA. moll3.92.021) and 5 paratypes (ZMA. moll3.92.022) in ZMAN.
Type locality: 4°36.4'S 130°21.7'E, 0-102 m depth, Snellius II Exped., Stat. 9 trawl 1, 2 August 1984.
Etymology: This species was first collected in the Banda Sea, hence the name bandaensis.