Description

Shells in this family are bubble shaped, dark colored, and have a sunken spire. The aperture is as long as the shell and usually comma shaped, while the columella has a callus without folds. The shells are very thin. None of the Bullidae have an operculum. The mollusc can retract deeply into the shell, and may achieve some further protection by wrapping its parapodia and a head shield over the shell. These mantle parts also secrete polypropionate metabolites that are toxic and deterrent to predation by fish (Marin et al., 1999). In this and other respects, the Bullidae differ from other opisthobranchs like the Haminoeidae.

 

The Bullidae seem to have split off at an earlier evolutionary stage, within the Cephalaspidea clade, and only one family is found in the suborder, Bullacea. Members of the family inhabit sands in shallow water. Although they have a gizzard and have been considered to be ommnivorous by many earlier observers, light and scanning electron micrography of gastric contents in species from various locations now indicate they are principally dependent on diatoms and, secondarily, small algae Malaquias et al., 2009. Nevertheless, there is a fairly extensive, older literature at least suggesting that the they and other Cephalaspideans can be somewhat opportunistic, as regards their dietary.

 

Within the Opisthobranchia informal group, many share very thin shells (Acteonidae, Haminoeidae, Bullinidae, Hydatinidae, Diaphanidae, etc. Taxonomic classification is not entirely settled among these families because not enough is known about either the anatomy or metabolies of the living molluscs.

 

Classification

Class: Gastropoda

Informal Group : Opisthobranchia

Clade: Cephalaspidea

Suborder: Bulloidea

Family: Bullidae

Single Genus: Bulla

• Species: Bulla ampulla  
• Species: Bulla botanica (Australian Bubble)
• Species: Bulla gouldiana  
• Species: Bulla striata (Common Atlantic Bubble)

Bulla gouldiana (Pilsbry, 1895)
California Bubble

Bulla ampulla (Linn., 1758)
Ampulle Bulla

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