Intraspecific variation in testis organisation and sperm head morphology of the delicate mouse (Pseudomys delicatulus): its possible causes and consequences
Eleanor Peirce A , TlalliAztlan Moya-Smith A C , Chris Leigh A D and William Breed B E
+ Author Affiliations
- Author Affiliations
A Medical School, University of Adelaide, Adelaide, SA 5005, Australia.
B Discipline of Biological Sciences, University of Adelaide, Adelaide, SA 5005, Australia.
C Present affiliation: Greater Lawrence Family Health Center, Lawrence, Massachusetts, USA.
D Present affiliation: Adelaide Microscopy, University of Adelaide, SA, Australia.
E Corresponding author. Email: bill.breed@adelaide.edu.au
Australian Mammalogy 44(1) 76-80 https://doi.org/10.1071/AM20057
Submitted: 26 August 2020 Accepted: 26 February 2021 Published: 30 March 2021
Abstract
The delicate mouse (Pseudomys delicatulus) ranges from Queensland to northern Western Australia. In this study the morphology of the cellular organisation of the testis and cauda epididymal spermatozoa are compared. Individuals from the mainland of the Northern Territory and Western Australia invariably have only 60–70% of the testes composed of seminiferous tubules with the interstitial tissue between the tubules containing abundant lipid rich Leydig cells, whereas the cauda epididymal sperm have highly polymorphic, often pear-shaped, heads and basally attached tails. In individuals from Queensland the seminiferous tubules make up approximately 80% of the testis, whereas in the cauda epididymides the sperm populations are generally less variable and have bilaterally flattened heads with the tail attached to the lower concave surface. These differences in the morphology of the delicate mouse testis and spermatozoa in these two geographic regions suggest differences in intensity of intermale sperm competition, with individuals from northern Western Australia and the mainland of the Northern Territory exhibiting monogamy whereas those from Queensland may exhibit some degree of intermale sperm competition and hence possibly have a polyandrous or promiscuous mating system. These findings support the suggestion that P. delicatulus, as currently recognised, contains at least one cryptic species.
Keywords: breeding system, cryptic species, delicate mouse, Pseudomys delicatulus, sperm competition, sperm head variability, testis morphology, testis organisation.
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