title: Micropyle number is associated with elevated female promiscuity in Lepidoptera.
abstract: In the majority of insects, sperm fertilize the egg via a narrow canal through the outer chorion called the micropyle. Despite having this one primary function, there is considerable unexplained variation in the location, arrangement and number of micropyles within and between species. Here, we examined the relationship between micropyle number and female mating pattern through a comparative analysis across Lepidoptera. Three functional hypotheses could explain profound micropylar variation: (i) increasing micropyle number reduces the risk of infertility through sperm limitation in species that mate infrequently; (ii) decreasing micropyle number reduces the risk of pathological polyspermy in species that mate more frequently; and (iii) increasing micropyle number allows females to exert greater control over fertilization within the context of post-copulatory sexual selection, which will be more intense in promiscuous species. Micropyle number was positively related to the degree of female promiscuity as measured by spermatophore count, regardless of phylogenetic signal, supporting the hypothesis that micropyle number is shaped by post-copulatory sexual selection. We discuss this finding in the context of cryptic female choice, sperm limitation and physiological polyspermy.
authors.affiliation: School of Life Sciences, Joseph Banks Laboratories, University of Lincoln, Lincoln LN6 7TS, UK giossa@lincoln.ac.uk.
authors.forename: Graziella
authors.identifier: 0000-0001-6813-4361
authors.initials: G
authors.lastname: Iossa
authors.affiliation: School of Biological Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK.
authors.forename: Matthew J G
authors.initials: MJ
authors.lastname: Gage
authors.affiliation: School of Life Sciences, Joseph Banks Laboratories, University of Lincoln, Lincoln LN6 7TS, UK.
authors.forename: Paul E
authors.identifier: 0000-0002-7159-936X
authors.initials: PE
authors.lastname: Eady
mesh_terms: D000818:Animals; D002080:Butterflies / Q000166:cytology / Q000502:physiology*; D005260:Female; D005306:Fertilization; D008297:Male; D009036:Moths / Q000166:cytology / Q000502:physiology*; D010063:Ovum / Q000166:cytology* / Q000502:physiology; D010802:Phylogeny; D012726:Sexual Behavior, Animal; D013093:Spermatogonia / Q000502:physiology
keywords: Lepidoptera; cryptic female choice; micropyle; polyspermy; sperm competition; spermatophore count