Orientation of Aplysia californica to distant food sources.

The behavior of the marine mollusc Aplysia was examined under different experimental conditions designed to determine the food searching strategy of the animals. In a small, open field tank with still water, the animals took an average of 42 min to find a piece of seaweed, even though the stimulus was never located more than 30 cm away from the animal. Observations of the animals indicated that their search was not directed, without a clear tendency towards the food, and during the course of a search, they often crawled through most of the area of the tank. The search time, the distance travelled, and the strategy of the search of the animals was similar for different types of seaweed. If animals were aroused into activity by the presence of seaweed extract, the time for them to contact a piece of odorless glass fiber paper in the open field was not significantly different than that for a piece of seaweed. The probability at which the animals contacted the seaweed, as a function of the distance travelled, resembled the detection probability determined according to a theory of random search. We thus propose that the aroused animals move in a random pattern until they are very close to the food. This strategy can be advantageous in still water since chemicals do not provide distinct gradients that can serve as cues for chemotactic orientation from distances greater than a few centimeters from the source. In a Y-maze in still water, Aplysia did not perform above chance in selecting the arm that contained the seaweed.(ABSTRACT TRUNCATED AT 250 WORDS)