A1 Journal article (refereed)
Asymmetries in reproductive anatomy : insights from promiscuous songbirds (2019)

Calhim, S., Pruett-Jones, S., Webster, M. S., & Rowe, M. (2019). Asymmetries in reproductive anatomy : insights from promiscuous songbirds. Biological Journal of the Linnean Society, 128(3), 569-582. https://doi.org/10.1093/biolinnean/blz100

JYU authors or editors

Publication details

All authors or editorsCalhim, Sara; Pruett-Jones, Stephen; Webster, Michael S.; Rowe, Melissah

Journal or seriesBiological Journal of the Linnean Society



Publication year2019


Issue number3

Pages range569-582

PublisherOxford University Press

Publication countryUnited Kingdom

Publication languageEnglish


Publication open access

Publication channel open access

Publication is parallel published (JYX)https://jyx.jyu.fi/handle/123456789/66466


Directional asymmetry in gonad size is commonly observed in vertebrates and is particularly pronounced in birds, where the left testis is frequently larger than the right. The adaptive significance of directional asymmetry in testis size is poorly understood, and whether it extends beyond the testes (i.e. side-correspondent asymmetry along the reproductive tract) has rarely been considered. Using the Maluridae, a songbird family exhibiting variation in levels of sperm competition and directional testis asymmetry, yet similar in ecology and life history, we investigated the relative roles of side-correspondence and sperm competition on male reproductive tract asymmetry at both inter- and intraspecific levels. We found some evidence for side-correspondent asymmetry. Additionally, sperm competition influenced directional asymmetry at each end of the reproductive tract: species experiencing higher levels of sperm competition had a relatively larger right testis and relatively more sperm in the right seminal glomerus. Within red-backed fairy-wrens (Malurus melanocephalus), auxiliary males had relatively more sperm in the left seminal glomerus, in contrast to a right-bias asymmetry throughout the reproductive tract in breeding males. Given that the number of sperm is important for competitive fertilization success, our results suggest that sperm competition shapes reproductive asymmetries beyond testis size, with likely functional consequences for male reproductive success.

Keywordsreproductive behaviouranatomyasymmetrytesticlesspermatozoapasseriformes

Free keywordsMaluridae; reproductive evolution; sperm competition; testis size

Contributing organizations

Ministry reportingYes

Reporting Year2019

JUFO rating1

Last updated on 2024-08-01 at 16:34