55 — Bubble shell, Bulla quoyii

Bulla quoyii, Mount Beach,
Mount Maunganui, 2015.

Bulla quoyii, Okahu Bay, Auckland, 28/11/15

Bulla quoyii (centre right), within it's
 mucous 'nest'. The light-coloured material
to the left is also part of the nest.
Okahu Bay, Auckland, 28/11/15.

There are a few species of bubble shell (Bullidae) in New Zealand. Bulla quoyii Gray, 1843 is the largest (~50mm) and one of the most common. It's found throughout North Island and the top of the South, plus southern Australia. They like sheltered waters and can often be found amongst sea grass meadows (Zostera sp.).

They are thought to be herbivorous, feeding on Enteromorpha sp. and other green algae (Malaquias et al., 2009). Rudman (1971) reported that in deeper sub-tidal waters they can also feed on red algae, e.g., Pterocladia lucida.

As with other Bulla species, they can sometimes be found within a mucous nest, which the snail builds. However, I've not yet been able to discern the function of this nest—perhaps it's an aid to camouflage at low tide or while the animal feeds...
















More info:

Malaquias, M. A. E., Berecibar, E., Reid, D.G., 2009. Reassessment of the trophic position of Bullidae (Gastropoda: Cephalaspidea) and the importance of diet in the evolution of cephalaspidean gastropods. Journal of Zoology, 27, 88–97.

Rudman, W. B., 1971. Structure and functioning of the gut in the Bullomorpha (Opisthobranchia). Part 1. Herbivores. Journal of Natural History, 5, 647–675.

Seaslug forum: http://www.seaslugforum.net/find/bullquoy