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RESEARCH ARTICLE
Contents Vol 108(1)

Reproductive anatomy of male Southern Emu-wrens (Stipiturus malachurus) and Striated Grasswrens (Amytornis striatus)

Melissah Rowe A B and Stephen Pruett-Jones A
+ Author Affiliations
- Author Affiliations

A Department of Ecology and Evolution, University of Chicago, 1101 East 57th Street, Chicago, Illinois 60637, USA.

B Corresponding author. Email: melissah@uchicago.edu

Emu 108(1) 68-73 https://doi.org/10.1071/MU07057
Submitted: 28 September 2007  Accepted: 12 February 2008   Published: 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.


Acknowledgements

We are grateful for the assistance and advice from Christina Rockwell, Wen Shen, Lionel Filewood, Jody Gates, Philippa Horton, David Hair, and David Turner. We thank Sarah Brown, Philippa Horton, and Jaynia Tarnawski for helping us with information regarding cloacal protuberances in emu-wrens and grasswrens. We are especially grateful to Belinda Cale for the cloacal protuberance data for the Thick-billed Grasswren. We also thank Trevor Price, Jill Mateo, and one anonymous reviewer for helpful comments on this manuscript. This research was supported by a National Science Foundation grant (to SP-J) and a Hinds Fund grant from the University of Chicago (to MR). All procedures were undertaken with approval from The University of Chicago Animal Care and Use Committee (ACUP# 71453). All work on the Striated Grasswren was approved by the Department of Environment and Heritage (South Australia) Wildlife Ethics Committee (Project No. 13/2004) and was conducted under a scientific permit (Q24832) and AW licence (No. 142). All work undertaken on the Southern Emu-wren was approved by the Director-General of New South Wales Department of Primary Industries Animal Care and Ethics Committee (Trim File No. 06/3846) and was conducted under a NSW NPWS scientific licence (S12048). Animals were administered pentobarbitone sodium under a permit to possess an S4 drug for administration (2006-60012). Finally, export of samples from Australia was approved by the Australian Government Department of Environment and Heritage (WT2005-10120 and WT2006-10958).


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