Annual cycle and morphology of lice parasitizing two sympatric African small mammals (Micaelamys namaquensis and Elephantulus myurus)

Abstract

Host-parasite relationships are complex because hosts use certain mechanisms (grooming, immune response) to get rid of the parasites while parasites try to evade these mechanisms. At the same time, these mechanisms are energetically costly to the host and can lead to poor body condition which in turn results in increased parasite infestation. Furthermore, the distribution and development of parasites are mainly affected by environmental (abiotic) and host/parasite (biotic) factors. Lice of the suborder Anoplura are permanent haematophagous ectoparasites that spend their entire life cycle on the host. Due to this close relationship, most studies have reported that lice are mainly affected by biotic rather than abiotic factors. Although parasites in general have become the focus of scientific research interest, the life history traits of sucking lice are still poorly understood. The current study aimed at evaluating the effects of abiotic and biotic factors on louse prevalence and abundance as well as their feeding and reproductive patterns. Furthermore, the study evaluated the impacts of abiotic and biotic factors on the on the body size of lice parasitizing two sympatric host species, namely the Namaqua rock mouse (Micaelamys namaquensis) and the Eastern rock sengi (Elephantulus myurus) from South Africa. Hosts were captured seasonally at two localities for a period of one year. All ectoparasites were collected (lice, ticks, mites and fleas) and host body weight and sex were recorded. Lice were identified and counted. Images of each louse specimen collected were taken at 45X magnification. Five body measurements (body length, abdomen length, abdomen width, head length and head width) were taken for each louse specimen using imageJ programme. A total of 454 M. namaquensis were captured of which 61 were infested with 975 lice from three species Hoplopleura aethomydis, Hoplopleura patersoni and Polyplax praomydis, but the prevalence and abundance for the latter were low. Furthermore, 147 E. myurus were captured and 23 were infested with 202 Neolinognathus elephantuli. All louse species (H. aethomydis, H. patersoni and N. elephantuli) exhibited different seasonal patterns in abundance. Hoplopleura aethomydis peaked in autumn, H. patersoni in summer and N. elephantuli peaked in winter. These patterns may be linked to differences in their life cycle length. Host age significantly affected louse abundance and this might be due to age-dependent differences in immune defences. Abiotic factors affected feeding patterns of all three louse species. Different reproductive patterns were observed between co-infecting H. aethomydis and H. patersoni. Only H. patersoni exhibited seasonal patterns in body size. Louse sex significantly affected the feeding patterns of lice except N. elephantuli. All louse species were sexually dimorphic (i.e. females larger than males) and this may be linked to different IV reproductive activities between sexes. This is the first study to analyse the effects of abiotic and biotic factors on the body size, feeding and reproductive patterns of sucking lice parasitizing small mammals. Therefore, future experimental studies manipulating these factors will shed more light on the impacts of these factors on the life history traits of lice.