The function of gonopodial parts and behavioral pattern during copulation by Gambusia (Poeciliidae)

Abstract

Through the use of movie film and artificial female models, the position of the pectoral fin and the manner in which gonopodial parts are used during copulation by male Gambusia were investigated. The evidence suggests that before gonopodial thrust and copulation, the gonopodium is folded, positioned below the pectoral fin, and twisted with gonopodial ray 3 rotating beneath ray 5. This permits the spines of ray 3 to face laterally and the elbow of ray 4a to project upward and possibly contact or even in some cases lock with the pectoral fin. During gonopodial thrust, males of all 14 species of Gambusia which were studied were observed on occasion to rotate their body until they faced head to tail with females and models. This body rotation is in a direction that helps to maintain the direction of twist and folding of the gonopodium.