ANATOMICAL ADAPTATIONS TO SPERM COMPETITION IN SMITHS LONGSPURS AND OTHER POLYGYNANDROUS PASSERINES

Authors
Citation
Jv. Briskie, ANATOMICAL ADAPTATIONS TO SPERM COMPETITION IN SMITHS LONGSPURS AND OTHER POLYGYNANDROUS PASSERINES, The Auk, 110(4), 1993, pp. 875-888
Citations number
47
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Ornithology
Journal title
ISSN journal
0004-8038
Volume
110
Issue
4
Year of publication
1993
Pages
875 - 888
Database
ISI
SICI code
0004-8038(1993)110:4<875:AATSCI>2.0.ZU;2-L
Abstract
I compared the reproductive anatomy of the polygynandrous Smith's Long spur (Calcarius pictus) with two other polygynandrous passerines (Dunn ock [Prunella modularis] and Alpine Accentor [P. collaris]) and with a wide range of socially monogamous species. All three polygynandrous s pecies were found to have enlarged testes and cloacal protuberances (i .e. the site of sperm storage) compared to species with other mating s ystems. Testes lengths in polygynandrous species averaged 44% longer a nd cloacal protuberances 213% greater in volume than expected for the body sizes of these species. Testes mass in Smith's Longspurs comprise d 4.2% of adult body mass or more than twice (2.0%) that found in the congeneric and monogamous Lapland Longspur (C. lapponicus). Smith's Lo ngspurs also had larger cloacal protuberances, larger seminal glomera and higher sperm stores, suggesting a greater overall rate of sperm pr oduction than in Lapland Longspurs. In contrast, females of polygynand rous species did not show any consistent differences in the pattern of sperm storage due to increased sperm production by males, although th is needs to be evaluated more thoroughly. The enlarged male reproducti ve organs of Smith's Longspurs and other polygynandrous species appear to have evolved as a consequence of sperm competition, whereby large sperm reserves function to insure paternity through diluting or displa cing the ejaculates of rival males.