Degeneration of CDCs and egg laying in the pond snail Lymnaea stagnalis

In the pond snail Lymnaea stagnalis egg laying is induced by multiple peptides, which are released by the neuroendocrine caudo-dorsal cells (CDCs). Egg laying in Lymnaea starts at about 50 days and increases initially with age to decreases again at an age of about 250 days. From that age on, the total number of animals that stop egg laying increases with age. The maximum age of Lymnaea is about 660 days. Lucifer Yellow fills of individual ventral CDCs showed reduced branching patterns in old animals. Immunocytochemical stainings demonstrated degeneration in ventral, dorsal and lateral CDCs. In animals that had stopped egg laying, CDCs could still be electrically activated. Regeneration studies after crushing the cerebral commissure showed that in old animals CDCs still can regenerate connections in the cerebral commissure. The properties of CDCs in old animals are discussed in relationship with possible mechanisms of cessation of egg laying in Lymnaea.