Emptying of the spermatophore and spermathecal filling in Culicoides melleus (Coq.) (Diptera: Ceratopogonidae)

Abstract

This paper completes the account of sperm transfer in Culicoides melleus. The events investigated here occupy the last 8 min of copulation and are concerned with transfer of spermatozoa and male accessory fluids to the spermathecae. It is proposed that transfer is effected by two complementary processes; the influx of fluid, by osmosis, into the spermatophore, and simultaneous withdrawal of fluid from the female system, principally the spermathecae. Arguments based on sperm motility as related to propagation of the flagellar wave of spermatozoa are developed to support these conclusions. Calculations show that the number of spermatozoa in the ejaculate cannot pass up the individual spermathecal ducts, by means of flagellar propulsion alone, within times that agree with observational data. The volume relationships of the spermatophore and female reproductive system are considered.