Anatomy & Physiology

Figure 1. Labelled diagram of dorsally opened
Littorina littorea with some transparency shown
for clearer anatomy. Redrawn from Fretter &
Graham, 1962.


Figure 2. Labelled diagram of a female Littorina littorea 
removed from its shell and viewed from the right side. 
The distinction between head-foot and the visceral mass
can be seen with the head-foot on the right of the mantle
edge (skirt) and the visceral mass on the left.
Redrawn from Fretter & Graham, 1962.

The anatomy of C. parthenopeum can be divided into two parts, the head-foot and the visceral mass. The visceral mass is contained within the shell and cannot be extruded. The head-foot on the other hand is capable of being extruded to achieve movement and feeding, and is readily retractable into the mantle cavity when in danger. This is achieved by the columellar muscle, which runs from the columellar to the head-foot (Graham, 1988).

Head-foot

Figure 3. Labelled diagram of the external anatomy
of the prosobranch, Buccinum undatum, with its
foot and proboscis extended.
Redrawn from After Cox, L.R., 1960
(Ruppert et al. 2004)


The head-foot is comprised of, as the name states, the head and foot of the animal. It is ventrally placed and bears the main sensory organs, penis in males, and also serves as its means of locomotion. The head consists of the mouth, cephalic tentacles and eyes. The other sensory organ, the osphradium, is located with the mantle cavity. The foot consist of the muscular part of the body with which the animal achieves locomotion. The operculum, a post-dorsal calcareous plate, can also be found on the foot. The operculum seals the aperture of the shell when the head-foot is retracted. (Ruppert et al., 2004; Graham, 1988).

Visceral mass

The visceral mass is located dorsally on top of the head-foot, containing the main viscera and bears the evidence of torsion (Kermack & Barnes, 1988).