Terminal Projection of Descending Interneurones Controlling Uropod Movements of the Crayfish Procambarus clarkii Girard

Abstract

Abstract Three types of descending interneurones (type A, B and C) that project into the terminal abdominal ganglion and control the movements of the uropod have been classified according to their physiological and morphological characters in the crayfish Procambarus clarkii (Girard) using intracellular recording and staining. They were activated by electrical stimulation of a small bundle of isolated fibres in a lateral portion of the ventral nerve cord containing the extension evoking fibres. The type A and B interneurones responded to each stimulus pulse with a spike in one-to-one fashion. The type A interneurones had antagonistic effects on uropod closer and opener motor neurones, while the type B interneurones coactivated both motor neurone types. The type C interneurones were activated indirectly by electrical stimulation and had antagonistic effects on the uropod motor neurones. The axons of the three types of interneurones descended in a dorso-lateral regions of the abdominal fifth–sixth connectiv...