Crayfish (Cherax destructor) use tactile cues to detect and learn topographical changes in their environment

When placed in a rectangular aquarium (arena) containing no objects, blindf olded freshwater crayfish (Cherax destructor) explore by walking along the walls of the arena. Animals taken from their home tanks and placed in the a rena for a 40-min trial each day habituate and exhibit a reduction in their exploratory activity over 4 trials, despite their lack of continuous expos ure to the arena. Dishabituation (i.e. an immediate increase in exploratory activity) occurs when animals were placed in the arena after the introduct ion of short partitions projecting at right angles from the walls. The dish abituation was interpreted as indicating that the animal can detect differe nces in the spatial configuration of the arena topography. Using dishabitua tion as a measure, we found that animals responded not only to the presence or absence of the partitions but also to changes in the position of the pa rtitions. Animals with immobilized or lesioned second antennae no longer re sponded to configurational changes in the spatial arrangement of the partit ions in the arena. We conclude that Cherax destructor relies upon the tacti le input from its second antennae to detect topographical changes in the en vironment and that such topographical changes can be retained for at least 24 h. For an organism that forages in and defends a home territory on a dai ly basis, this seems to be an ecologically relevant time scale.