Zool 250
Best Annotated Bibliography 2002
Submitted by Kate Witkowska

Copeland, J. and M.M. Daston. 1989. Bioluminescence in the terrestrial snail Dyakia striata. Malacologia 30:317-324.

Bioluminescence is a widely occurring phenomenon throughout the animal kingdom and yet its adaptive function is generally poorly understood. Dyakia striata is the only known terrestrial mollusk to display this trait. Of what adaptive benefit might light emission then be to this species of snail?

Not all D. striata are capable of bioluminescence. Those that do, possess a luminescent organ located in the head-foot region of the body. It produces flashes of yellow-green light that vary in wavelength, duration and frequency. When irradiated with ultraviolet light, it fluoresces.

Snails were divided into two groups, based on their relative size (small and medium). Behavior patterns like locomotion, feeding and resting were observed in all snails under controlled conditions, which included variables like: air temperature and humidity as well as food, space and light availability. Experiments tested D. striata's response to flashes emitted from another species member and from an artificial source. In both cases, snails responded by increasing the frequency of light signal emission. In some cases 'natural' signaling resulted in physical contact between the snails. Most of the time, flashing occurred in active animals (moving or feeding).

The researchers found that flashing of one D. striata influenced flashing and, possibly, movement of a second snail. Bioluminescence was given behavioral function. They proposed that this form of signaling aids intraspecific communication, and furthermore is being used for aggregation of individuals.

(229 words)

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(posted Jan. 2003)