[The generation of locomotor rhythmicity in the nervous system of large and small individuals of the pteropod mollusk Clione limacina].

The marine pteropod mollusc Clone limacina swims due to rhythmic movements of its wings. The frequency of wing oscillations in young molluscs (2-6 mm long) is 5-6 Hz, while in adult molluscs (40-60 mm long) it is 1-2 Hz. The locomotor rhythm is generated by two groups of pedal interneurons (groups 7 and 8) capable of endogenous rhythmic activity. The interneurons generate prolonged action potentials, one potential per a locomotor cycle. Action potentials generated by interneurons in young molluscs are found to be shorter (30-40 ms) than in adult ones (100-150 ms). This difference in duration of the action potentials is a result of the higher frequency of the locomotor rhythm in young molluscs as compared with adult ones.