Homing behaviour and possible cognitive maps in crustacean decapods.

This review on homing in decapods, which has been shown by Herrnkind (1983) and Wehner (1992), indicates how scarce our knowledge is, not only on the physiological mechanisms involved in such behaviour but also on the reality and extent of the behaviour itself. The case studies cited (first part) show that among decapods (only ''reptants'' are considered here), some species seem to wander at random, some can keep within a more or less well defined home range with no particular ''home'' while yet others are known to relocate periodically a definite restricted goal. Although burrows and shelters are the primary homing goals, cases of relocation of food resources and mates have also been reported. Some decapods occupy a single shelter, while others tend to visit, on a more or less regular basis, a system of shelters. The second part of this review deals with the mechanisms involved in decapod homing. Apart from idiothetic mechanisms, visual cues certainly play the most important role among terrestrial or semi-terrestrial species. Chemical cues may play a role in benthonic species, although direct evidence for this is still lacking. In certain cases a cognitive map relying on a system of orienting cues can be inferred.