27 September 2005

A colorful predator: Gulella bicolor

This strikingly colorful land snail, sometimes placed in the subgenus Huttonella, is not native to the U.S. Its original homeland may be South Africa or India. It was first recorded in the U.S. in the early 1950s1. I found this specimen last July near Fort Myers, Florida.

Gulella bicolor, whose shell grows to be about 7 mm long, is a predator of other equally small snails. In one study, starving captive individuals of G. bicolor did not eat several plant species given to them2, suggesting that they are strict carnivores. Fortunately for native snails, Gulella's main prey appears to be Subulina octona, another introduced snail in southern U.S. I kept two specimens of Gulella for about a month and fed them very small juveniles of Subulina. Unfortunately, I didn’t have a chance to photograph the predators in action.

The information on this snail at some web sites is inaccurate. For example, the description at the Gulf States Marine Fisheries Commission web site states that “Living specimens appear two-toned since the shell is red-orange anteriorly, and yellow posteriorly.” It is not the shell that is colored red and yellow, but the snail’s body. The shell itself is translucent white.

1. Dundee, D.S. 1974. Catalog of introduced molluscs of eastern North America. Sterkiana. No. 55:1-37.
2. Dundee, D.S., and R.J. Baerwald. 1984. Observations an a micropredator, Gulella Bicolor (Hutton) (Gastropoda: Pulmonata: Streptaxidae). Nautilus 98:63-68.


Cindy M. said...

I find it utterly fascinating that this species has a transparent shell- I would never have been able to tell that from your photo, what an interesting little snail. Excellent photos too :)

Marcus said...

This species is recorded in Singapore and Malaysia too, see: rmbr.nus.edu.sg/rbz/biblio/43/43rbz091-113.pdf