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Reproductive anatomy of male Southern Emu-wrens (Stipiturus malachurus) and Striated Grasswrens (Amytornis striatus)
Melissah
Rowe A B,
Stephen
Pruett-Jones A
A
Department of Ecology and Evolution, University of Chicago, 1101 East 57th Street, Chicago, Illinois 60637, USA.
B
Corresponding author. Email: melissah@uchicago.edu
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Emu 108(1) 68–73 http://dx.doi.org/10.1071/MU07057
Submitted: 28 September 2007
Accepted: 12 February 2008
Published online: 13 March 2008
Abstract
In birds, several features of male reproductive anatomy vary with the degree of promiscuity and the intensity of sperm competition. We describe the male reproductive anatomy of the Southern Emu-wren (Stipiturus malachurus) and the Striated Grasswren (Amytornis striatus) in the context of sperm competition. Male Southern Emu-wrens exhibited a very low relative testes size of just 0.6% of male body mass, lacked a cloacal protuberance and possessed a relatively small seminal glomera containing an average of just 12.6 × 106 sperm. Male Striated Grasswrens exhibited relatively small testes, comprising 1.78% of male body mass, and small cloacal protuberances. The relative size of the seminal glomera was also small and seminal glomera contained an average of 42.5 × 106 sperm. When compared with the well-studied fairy-wrens (Malurus) and based on male reproductive anatomy, it appears that emu-wrens experience a relatively low level, and grasswrens an intermediate level, of sperm competition.
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