Summary

Cymatium (Monoplex) parthenopeum belongs to the family Ranellidae, also known as Cymatiidae, and are also part of the Prosobranchs, formerly Prosobranchia. The family consist of molluscs gastropods that have medium to large sized heavy shells which are made up of multiple varices and covered with a brownish yellow coloured periostracum. Species found in Australia have only been recently discovered in other parts of the world, resulting in locally named species adopting older European names, with some Australian names kept as names of subspecies in some cases (Beu, 1985). 

C. parthenopeum are completely torted, snail shaped animals with a spirally coiled shell and asymmetrical visceral mass. They have a well developed head which bears a pair of cephalic tentacles as well as lateral eyes located at the base. It achieves locomotion via a wide creeping foot. It has a single monopectinate ctenidum (gill), gonopore, nephridiopore and anus which can be found in the mantle cavity. The gut is U-shaped due to torsion. It has a prosobranch heart that is made up of a ventricle and one or two atria. Its streptoneurous nervous system is coupled with well developed sensory organs such as eyes, osphradium, statocysts and chemoreceptive organs. The columellar muscle which runs from the foot to the visceral mass is responsible for the retraction and extrusion of the head and foot from the mantle cavity (Ruppert et al., 2004). They are gonochorisitic, oviparous animals which produce teleplanic veliger larvae (Ruppert et al., 2004; Pechenik et al., 1984).

Gastropods in this family are also carnivores, either active hunters, grazers or scavengers. C. Parthenopeum has been observed as a carnivorous grazer, feeding on bivalves and ascidians, using its radula and possibly secretions from its salivary glands to subdue and consume its prey (Laxton, 1971).