DIETARY CHOLINE REQUIREMENTS FOR SPERM MOTILITY AND NORMAL MATING ACTIVITY IN DROSOPHILA MELANOGASTER

¹ Department of Biology, Knox College, Galesburg, Illinois 61401

1. Adult D. melanogaster raised on a carnitine-supplemented diet fail to reproduce unless choline is included in their diet. The sterility is due primarily to a lack of motile sperm but carnitine-raised adults also mate much less readily than choline-raised adults. Carnitine-raised females are fertile, however, when inseminated by choline-raised males. Supplementation of the diet with 5.7 x 10^-4 M choline for 5 days will correct the sterility of carnitine-raised males provided 7 additional days elapse before the fertility test. All males possess some motile sperm by day 8 following the initial choline meal but females mated to test males do not lay eggs that hatch at the optimal level until day 12. Thus, 5 days of feeding are required for the accumulation of sufficient choline for optimal fertility but it is not until 7 days after the choline feeding period that a maximum number of motile sperm are formed. A choline meal of less than 5 days in duration results in less than optimal male fertility, whereas a feeding period longer than 5 days is required for optimal fertility if choline is fed at a concentration less than 5.7 x 10^-4 M. The choline requirement for the development of motile sperm is very specific; betaine homocholine, sulfocholine, diethylcholine, monoethylcholine, carnitine, -methylcholine, 2-dimethylaminoethanol, and 2-methylaminoethanol failed to substitute for choline.

2. Choline may be required for the synthesis of phospholipid needed as an energy source for sperm motility. This requirement would be similar to the requirements of many vertebrate and invertebrate spermatozoa for a choline-containing phospholipid as an endogenous energy source for motility. Since D. melanogaster can not synthesize choline, the choline needed for sperm motility must be supplied by the diet.