The relationship between immunocompetence, parasite load and reproductive effort in the highveld mole-rat (Cryptomys hottentotus pretoriae) Roberts 1913.

Abstract

Life-history theory is based on the notion that resources are generally limited in nature, and that organisms have to allocate these resources amongst different physiological systems to maximise their survival and fitness. Therefore life-history traits such as maintenance, growth and fecundity are very often negatively associated with each other. Since the immune system plays a prominent role in fitness and survival of an organism it often features in life-history trade-offs particularly with respect to reproductive effort. This thesis focused predominantly on the interactions between immune function and reproductive effort in the highveld mole-rat, Cryptomys hottentotus hottentotus as well as other factors that may influence these two vital systems. In the first chapter interactions between reproductive effort and immune function in 22 female highveld mole-rats (5 reproductive females and 17 non-reproductive females) is investigated by stimulating reproductive competition amongst females within colonies and monitoring hormonal and haematological parameters. Behavioural observations focusing on agonistic, grooming and sexual behaviour is also included in this chapter mostly as tool to identify reproductive competition amongst females. The second chapter deals specifically with the effect of the season, gender and reproductive status on a febrile response to an exogenously administered pyrogen. Lipopolysaccharide, a protein produced by gram negative bacteria, was used to induce fever in 37 mole-rats during both winter and summer months. The final chapter explored the relationships between parasite infestation and host gender and reproductive status while concurrently identifying some of the parasites associated with the highveld mole-rat. A total of 46 mole-rats were assessed for intensity of gastrointestinal parasites, 131 for prevelance of cestodes by faecal examination and 85 for intensity and prevalence of ectoparasites. A possible relationship between host group size and intensity of parasitism is explored. Seasonal patterns of the parasites found is also investigated and related to possible seasonal variation in immune function.