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Are non-reproductive male highveld mole-rats, Cryptomys hottentotus pretoriae physiologically suppressed while in the confines of the natal colony?

Published online by Cambridge University Press:  01 May 2003

L. Janse van Rensburg ,
N. C. Bennett ,
M. van der Merwe ,
A. S. Schoeman  and
J. Brinders
L. Janse van Rensburg
Affiliation:
Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa
N. C. Bennett
Affiliation:
Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa
M. van der Merwe
Affiliation:
Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa
A. S. Schoeman
Affiliation:
Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa
J. Brinders
Affiliation:
Department of Veterinary Physiology, Onderstepoort, Pretoria 0002, South Africa
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Abstract

The highveld mole-rat, Cryptomys hottentous pretoriae is a social, subterranean, co-operative breeder with a high reproductive skew. The relationship between reproductive status and reproductive physiology in male highveld mole-rats was investigated. Testicular morphometrics, histological parameters, plasma testosterone concentrations and sperm motility parameters were studied in 31 males (14 reproductive and 17 non-reproductive males). Reproductive males were significantly larger than non-reproductive males, with testicular mass and volume corrected for body mass considerably larger for the reproductive males. Circulating plasma testosterone concentrations of reproductive males were not significantly higher than non-reproductive males (reproductive males 10.3±1.8 nmol l−1vs non-reproductive males 7.3±1.74 nmol l−1). Sperm motility parameters were measured, but no significant differences were found between reproductive and non-reproductive males. All 14 reproductive males had motile sperm, whereas 13 of the 17 (76%) of non-reproductive males possessed motile sperm. A typical ejaculate of a reproductive male contains 48.3% motile sperm characterized by a high percentage of flagellar defects, whereas the non-reproductive male has an ejaculate containing 45.6% motile sperm with a high percentage of head defects. It is apparent that non-reproductive males are not physiologically suppressed from reproducing. Moreover, the non-reproductive males are excluded from incestuous matings as a result of being the offspring of the reproductive female.

Keywords

mole-ratCryptomysreproductionspermatozoamotilitysuppression
Type
Research Article
Information
Journal of Zoology , Volume 260 , Issue 1 , May 2003 , pp. 73 - 78
Copyright
2003 The Zoological Society of London

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