Making more than one type of sperm – how do flies and moths do it?

Sperm heteromorphy (the production of more than one type of sperm) has evolved independently in a wide range of animals from insects, to molluscs, to fish. In these species the distinct sperm morphs differentially function in fertilisation and post-mating processes in the female reproductive tract indicative of specialisation within a fundamentally critical biological process. However, very little is known about how the morphology of different sperm types is reproducibly generated.

We have used both a dipteran Drosophila pseudoobscura, which makes three sperm types, and a lepidopteran Galleria mellonella, which makes two sperm types, to investigate the transcriptional regulation of differential sperm morphogenesis. RNAseq of single, cytologically identical, pre-meiotic spermatocyte cysts identified genes that are differentially expressed or alternatively spliced between cells with different developmental fates in both systems. Many genes predicted to function in transcription, cell cycle regulation, spermatid elongation and morphology were differentially expressed between primary spermatocytes destined to become different sperm. We discovered recently duplicated genes that showed differential expression of paralogues between morphs, suggesting that gene duplication and sub- or neo-functionalisation could be a driver of sperm specialisation.

Learn more about the speaker for this event