AGE-RELATED DEFICITS OF LONG-TERM-MEMORY IN THE CRAB CHASMAGNATHUS

Short- and long-term memory in adult crabs Chasmagnathus granulatus of different age are evaluated in two learning paradigms: habituation to a visual danger stimulus and appetitive conditioning. No difference b etween young, middle-aged and aged animals is found in short-term habi tuation with 15 training trials. A good level of retention of the habi tuated response at 24 h is exhibited by young and middle-aged crabs bu t a poor one by aged crabs. When the training-to-testing interval is l engthened to 48 h or the training session reduced to 7 trials, young a nd middle-aged crabs continue to show long-term habituation but aged i ndividuals exhibit no retention at all. As regards appetitive conditio ning, young, middle-aged and aged crabs present similar short-term mem ory with 5 training trials and similar long-term memory when tested at 24 h, but an age-related deficit in long-term retention is exhibited when the intersession interval is lengthened to 48 h or the training r educed to 3 trials. Thus, a reduction of long-term memory related to a ge is demonstrated in the crab Chasmagnathus. Since it is shown in two different learning paradigms, the possibility of explaining the defic it in terms of a failure in memory mechanisms due to aging rather than as a consequence of ontogenetic shift in the crab's behavior is discu ssed.