Clio andreae

Clio andreae (Boas, 1886a)


This is a shelled, uncoiled, pyramidally shaped, pelagic snail, up to 2 cm long. The shell is transparent, broadly triangular and oval in cross-section. The black body and visceral mass shines through the transparent shell. Growth lines are not prominent, the lateral sides are rounded in cross section. It is a good swimmer that feeds on phytoplankton and protozoa. It lives in the deep waters of all oceans. The juveniles are found at shallower depth (Clio andreae drawing, Clio andreae in perspective).

Taxonomic Description

Clio andreae has a straight shell, except for the posterior point which abruptly curves dorsally, it is slender and thin (Clio andreae in perspective). The ventral side is somewhat more convex than the dorsal one. The lateral ribs are well developed (Clio andreae lat.rib), straight and regularly diverging. The longitudinal ribs on dorsal and ventral sides and the transverse striation are faint or absent, both sides are flattened. (Clio andreae). The rear angle of the shell is small. Near the aperture the shell width is about one half to one third of the total shell length. The embryonic shell is separated from the rest of the shell by a clear ring. The embryonic shell is round without a terminal cusp, and curved ventrally in regard to the caudal point of the shell. Recently in the NW-Indian Ocean specimens with a cusp on the embryonic shell are found. The lateral ribs are not excavated, like in Clio balantium. The soft parts are dark brown to black and the posterior footlobe is very large (Clio andreae soft parts). The Clio andreae radula formula is 1-1-1.
The shell measures up to 20 mm long, and is 5 times as long as broad.


The juveniles are provided first with a perfectly round protoconch I that later grows out with the broad cylindrical protoconch II. A small cusp is sometimes present at the posterior tip but this is quickly worn off. Protoconch II does not have growth lines close together as in Gymnosomata. Still these Gymnosomata are frequently identified as Clio andraea or Clio polita (Almogi-Labin and Reiss, 1977).


Clio andreae is a protandric hermaphrodite. Strobilation may occur, in these cases the body is separated in two parts; a vegetative anterior section that swims away and a part that stays in the shell and that is entirely composed of reproductive tissues (Pafort-van Iersel and Van der Spoel, 1986). For a description of the strobilation see also Clio pyramidata.


Clio andreae is a phytophage and mesopelagic.


Clio andreae is a bathypelagic species found in the Atlantic Ocean where it penetrates far north into the Gulf Stream area, only three small populations have been found south of 5°N, viz. one off Cape Blanco, one off Cape Good Hope and one in the Argentine Basin. A single record is known from the Indian Ocean. It is also common in the N-Pacific Ocean, see the Clio andreae map. Dubious records in the Gulf of Panama and off California suggest that a large Pacific population is also present.
From the Mediterranean only few living specimens have been recorded (Rampal, 1966), but dead shells, perhaps, subfossil, have been frequently found.
Most authors consider this species as bathypelagic, while it is always emphasized that the young live near the surface in the upper 200 m. The temperature ranges from 3.32° to 6.21° C and salinity from 34.4o/oo to 35.55o/oo.

Geological Record

This species was known from the Late Quaternary of the Red Sea and the Pleistocene of the Mediterranean.


Cleodora andreae Boas, 1886: 80, 203, pl. 1, fig. 1, pl. 2, fig. 12, pl. 4, fig. 49, pl. 5, fig. 92 (Clio andreae type).
Holotype ZMUC damaged specimen (alcohol collection) and one radula slide in ZMUC.
Type locality: 33°30'S 11°E, Coll.: Andréa.