Sperm precedence, mating interval, and a novel mechanism of paternity bias in a beetle (Tenebrio molitor L.) |
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Authors: | J M Drnevich E F Hayes R L Rutowski |
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Institution: | (1) Department of Biology, Arizona State University, Tempe, AZ 85287-1501, USA e-mail: drnevich@asu.edu Tel.: +1-480-9654365, Fax: +1-480-9652519, US |
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Abstract: | When females mate with more than one male, the ensuing sperm competition leads to the evolution of male mechanisms that skew
paternity. Males of the yellow mealworm beetle (Tenebrio molitor) transfer a spermatophore to females during copulation, but sperm release and storage occur later. We investigated how the
interval between two matings with different males affects sperm precedence by varying the interval between the copulations
so that the second mating was either: (1) before sperm release from the first spermatophore (<5 min); (2) after sperm release
but before spermatophore ejection (15–20 min); (3) after spermatophore ejection but before sperm storage (4 h), or (4) after
complete sperm storage (24 h). We collected offspring over a period of 2 weeks and determined paternity by protein electrophoresis.
There was second-male sperm precedence in all treatments, but when the interval was <5 min, the second male usually (86% of
cases) had complete sperm precedence (i.e., P
2=1). Investigations into the mechanism of second-male sperm precedence during <5-min mating intervals indicate that sperm
release from the first spermatophore is inhibited, a phenomenon which has not been previously documented.
Received: 31 January 2000 / Revised: 9 June 2000 / Accepted: 26 August 2000 |
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Keywords: | Mating intervals Sperm precedence mechanisms Spermatophores Tenebrio molitor |
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