FEMALE REPRODUCTIVE AGING IN THE POND SNAIL LYMNAEA-STAGNALIS

Egg laying activity of the pond snail Lymnaea stagnalis changes with a ge. Initially there is an increase of egg laying activity. At an age o f about 250 days egg laying activity starts to decrease and eventually ceases. Lymnaea thus has a clear post-reproductive period during its life cycle. In order to locate mechanisms which are responsible for th e cessation of egg laying activity electrophysiological, behavioural a nd injection experiments were done and the morphology of the neurons c ontrolling egg laying activity (the caudodorsal cells, CDCs) were stud ied. On the basis of the results of the foregoing experiments and obse rvations it is hypothesized that due to degeneration of particular CDC s in old animals, input to the egg laying control system is terminated resulting in cessation of egg laying.