Independent evolution of atypical sperm morphology in a passerine bird

Spermatozoa exhibit striking morphological variation across the animal kingdom. In passerine birds, sperm exhibit considerable variation in size, yet the basic sperm phenotype is highly conserved; sperm are filiform, the head is corkscrew-shaped, and the midpiece is elongated and twisted around the flagellum. A significant departure from this typical sperm morphology has been reported in the sister species, the Eurasian bullfinch (Pyrrhula pyrrhula) and Azores bullfinch (P. murina). Here, we report a second evolutionary shift in passerine sperm phenotype in the nominate subspecies of the red-browed finch (Neochmia temporalis temporalis); sperm are non-filiform, with an ellipsoid head, and an extremely short midpiece restricted to the nuclear-axoneme junction. Additionally, we show that the sperm phenotype of the red-browed finch is similar to the putatively neotenous sperm described in the two bullfinch species. Using whole-genome data, we found no evidence that the unusual sperm phenot..., , , # Independent evolution of atypical sperm morphology in a passerine bird

Authors:
Melissah Rowe¹*, Daniel M. Hooper², Antje Hofgaard³, Laura L. Hurley⁴, Callum S. McDiarmid⁴, Ioanna Pataraia¹, Jan T. Lifjeld⁵, and Simon C. Griffith⁴

1 Department of Animal Ecology, Netherlands Institute of Ecology (NIOO‐KNAW), 6700 AB, Wageningen, The Netherlands.
2 Institute for Comparative Genomics and Richard Gilder Graduate School, American Museum of Natural History, New York, NY 10024, USA.
3 Electron Microscopical Unit for Biological Sciences, Department of Molecular Biosciences, University of Oslo, 0316 Oslo, Norway.
4 School of Natural Sciences, Macquarie University, Sydney, NSW 2109, Australia.
5 Natural History Museum, University of Oslo, 0318 Oslo, Norway.

* Author for correspondence: [[e-mail]](mailto:[e-mail])

In this study, we gather raw data on sperm size to investigate sperm morphology (sperm length) in the Australian Estrildidae grassfinch, the red-browed finch...,