Late Lunch Talk: A Molecular Evolutionary Approach to Sperm Heteromorphism
Late Lunch Talk by Emma Whittington
This Late Lunch Talk will be held on Zoom:
Meeting ID: 662 2886 1051
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Sperm heteromorphism is the enigmatic phenomenon in which a male produces multiple discrete sperm morphs in a single ejaculate, only one of which is fertilisation competent. We applied mass spectrometry-based proteomic techniques to the origin and maintenance of sperm heteromorphism in two species of butterflies and moths. In this taxonomic order, the incompetent sperm lack nuclear DNA entirely, with genomic content ejected during spermatogenesis, and often make up the majority of sperm produced by a male. Although it seems counterintuitive for males to invest presumably a considerable amount of resources into infertile sperm, sperm heteromorphism is almost universal in butterflies and moths. We characterised and compared the proteomes (all proteins contained within a sample) of both sperm types in the monarch butterfly (Danaus plexippus) and Carolina sphinx moth (Manduca sexta). Our results identified a burst of genetic novelty within this order, concurrent with the origin of sperm heteromorphism. Additionally, our comparative analysis of sperm types revealed that the infertile sperm type diverged more rapidly and was less complex with evidence of lineage specific gene loss. This may be consistent with a relaxation of selective constraints associated with fertilisation or adaptive responses to sexual selection.