Diacria danae

Diacria danae Van der Spoel, 1968a


This is a small, uncoiled, shelled thecosomatous pteropod, 0.2 cm or less long. It is globular with rounded ventral and dorsal sides and well developed ribs. The lateral spines are small. The caudal spine is absent as, in juveniles, the protoconch is broken off, leaving only a mark. Shell sculpture consists of faint growth lines and 3 dorsal striae. Micro- zooplankton and phytoplankton are its food and it is a mucus feeder. It lives in all oceans (Diacria danae).

Taxonomic Description

The rather globular shell is red-brown and semi-transparent. The dorsal lip is arch-shaped and borders a very narrow shell aperture. The ventral and dorsal sides are both heavily vaulted, and have striae near the aperture lips. The caudal spine mark is oval. Between the small lateral spines and the corners of the spine mark the curved lateral sides are thickened. Usually a faint median depression is present on the ventral side and lip. The aperture lips are thickened. A pair of closing mechanisms, less developed than in Cavolinia, are found in the aperture. The radula formula is 1-1-1. The dorsal ribs are typical, transverse striae on dorsal and ventral surfaces are moderately developed, the ventral surface is regularly vaulted, the lateral spines are well developed, about three dorsal striae are imbricate. (Diacria danae ventral ribs). In this species a 'Subtropical' and an 'Equatropical' form are distinguished (Leyen and Van der Spoel, 1982) which are separated on shell sizes only. As this is not a good taxonomic character they are not treated separately.
Shell length 1.4-2.1 mm, shell width 1.1-1.7, diameter of caudal spine mark 0.56-0.80 mm.


The juveniles closely resemble those of Diacria costata which are only slightly smaller. Like in all Diacria species, the juvenile shell are thrown off in adults leaving a mark (Diacria danae caudal spine mark).


This species is a protondric hermaphrodite.


This species is phytophagous.


This species lives in the Equatorial and Central waters of all oceans, see the Diacria danae map.

Geological Record

This form was found in the Pleistocene of the Mediterranean.


Diacria quadridentata forma danae Van der Spoel, 1968: 217, fig. 1.
Holotype: ZMUC (alcohol collection). Paratypes: ZMUC 11 spec. (alcohol collection).
Type locality: 2°57'S 99°36'E. Coll. CDAE, stat.3860vii.