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Diacria maculata Bleeker and Van der Spoel, 1988

Overview

This is a medium sized pelagic snail, 0.9 cm broad. It has a typical colour patterns. The shell is uncoiled bilateral symmetrical with a long, sometimes broken, caudal spine. The colour pattern on the dorsal side consists of a continuous band of brown colour along upper and lateral shell margins; a separated patch of colour is found on the caudal half of the median dorsal rib. Ventrally a continuous band is found along upper and lateral shell margins, an irregular quadrangular colour patch is found on the upper half of the ventral side as well as a patch on the narrowing caudal part of the ventral side. It feeds on small plankton mainly phytoplankton in the epi- and mesopelagic depth of W-Atlantic and Pacific Oceans (Diacria maculata dorsal).

Taxonomic Description

The straight and sharp lateral spines are directed slightly caudally. The closing septum is of equal size as in Diacria t. tripsinosa. The dorsal side has 3 moderately developed ribs. The central rib is most elevated in the caudal part, the lateral ones in the middle. The lateral sides, between the spines and closing septum, are nearly straight and form an angle of 109°. Growth lines are evident on both sides. The colour pattern on the dorsal side consists of a continuous brown band along upper and lateral shell margins; a separated patch of pigment is found on the caudal half of the median dorsal rib. The ventral colour pattern (Diacria maculata 1) forms a continuous band along upper and lateral shell margins, an irregular quadrangular colour patch is found on the upper half of the ventral side as well as a patch on the narrowing caudal part of the ventral side. The upper lip is curved slightly dorsally. The ribs on the ventral side are distinct, the ventral aperture lip curves prominently ventrally.
The shell width is 8.8 mm, shell length is 7.3 mm, length between the lateral spines and closing septum is 3.2 mm, the distance between lateral spines and centre of upper lip is 5.7 mm, the width of shell aperture is 3.2 mm, the height of shell aperture 0.72 mm,and the aperture angle between lateral sides 109°.

Juveniles

The juvenile has a long dorso-lateral flattened needle-like shell with the lateral sides only diverging anteriorly. The protoconch I is globular. There is no sculpture on protoconch I or II. The lateral sides of protoconch II are thickened.

Reproduction

This species is a protandric hermaphrodite.

Ecology

This species is phytophagous. The shell is frequently covered by hydropolyps. It swims with two wings and sinks with retracted wings.

Distribution

This species is known from recent sediment samples in W-Atlantic and W-Pacific Ocean, see the Diacria maculata map.

Types

Diacria maculata Bleeker and Van der Spoel, 1988: 61, fig. 4, 5, 8, 9.
Holotype: USNM 283052 and 8 paratypes USNM 859099 Albatross Exp. stat. 5470, 560 fms estimated depth.
Type locality: sediment sample, Philippines, Lagonboy Gulf E. Luzon, 13°37'30"N 123°41'09"E.
Etymology. This species is named for the dorsal and ventral colour spot (maculata).

Diacria maculata