Reproductive seasonality in the Tete veld rat (Aethomys ineptus) (Rodentia: Muridae) from southern Africa

Authors

  • S. P. Muteka,

    1. Mammal Research Institute (MRI), Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
    2. Department of Animal Science, University of Namibia, Windhoek, Namibia
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  • C. T. Chimimba,

    1. Mammal Research Institute (MRI), Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
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  • N. C. Bennett

    1. Mammal Research Institute (MRI), Department of Zoology and Entomology, University of Pretoria, Pretoria, South Africa
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Correspondence
Christian T. Chimimba, Mammal Research Institute (MRI), Department of Zoology and Entomology, University of Pretoria, Pretoria, 0002 South Africa.
Email: ctchimimba@zoology.up.ac.za

Abstract

Very little is known about the reproductive biology of the recently recognized Tete veld rat Aethomys ineptus. In the present study, we investigated the seasonality of reproduction in this newly recognized rodent using a number of histological and endocrinological parameters. Body mass, reproductive tract morphometrics, gonadal histology, and plasma testosterone concentrations in males and plasma oestradiol-17β and progesterone concentrations in females were assessed from a population in the north-central part of South Africa over a 12-month period in order to ascertain the pattern of reproduction in the species. Seminiferous tubule diameters in 59 males were significantly larger between September and February relative to between March and August. Although spermatogenesis was prevalent in the southern hemisphere winter (June–August), the number of spermatozoa in the epididymides decreased in the southern hemisphere spring (September–November), summer (December–February) and autumn (March–May). Testicular mass relative to body mass and testicular volume regressed between May and September but exhibited recrudescence between September and April, whereas plasma testosterone concentrations increased significantly between September and February relative to between March and August. Ovarian histology of 67 females showed corpora lutea to be present throughout the year, but decreased in number during winter, whereas mean plasma progesterone concentration increased significantly between August and November and again between February and April. This bimodal pattern of progesterone concentration suggests that up to two litters per breeding season may be raised by the Tete veld rat. Gravid females were found between October and April, whereas gravid or lactating females were conspicuously absent between May and September. Collation of all these data suggests that the Tete veld rat is a seasonal breeder with reproduction confined predominantly to summer and autumn months of the southern hemisphere. However, the presence of follicular development in females and the presence of corpora lutea outside the breeding season imply that the Tete veld rat may undergo spontaneous ovulation.

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