Parasite load of nematode species in Apodemus flavicollis: Effects of host spleen size, body mass, body condition and sex

Abstract

Background. In wild populatons of small rodents, different intrinsic and extrinsic factors affect variation in parasite burdens. The energetc status of animals has a great impact on the immune system, while environmental factors can change the relatonship between infecton and the host body conditon. We aimed to analyse the relatonship between relevant morphological traits and parasitological parameters in populatons of yellow-necked mice, Apodemus flavicollis (Melchior, 1834). Material and Methods. Nematode burdens were assessed in 49 A. flavicollis, from 7 different localities in Serbia. Morphometric data were measured for all captured mice. Spleen mass was used as a proxy of immunocompetence. The host body conditon, individual parasite load (IndPL), individual parasite species richness (IndPSR), prevalence, mean abundance and mean infecton intensity were calculated. Results. A total of 12 nematode species were recorded in A. flavicollis. The overall prevalence of infection was very high (100%). Individual parasite species richness (IndPSR) was signifcantly positvely correlated with body conditon (R2=0.173; p=0.003), and the same patern was observed in both sexes. Spleen size was also signifcantly positvely correlated with body conditon (R2=0.344, p<0.005) and body mass (R2=0.341, p<0.005). Contrary to expected, no parasitological indices (IndPSR and IndPL) were signifcantly related to spleen mass. Conclusion. Animals exhibitng beter body conditons are parasitzed simultaneously with a higher number of nematode species (i.e. their parasite infracommunites are richer). This could prevent any of them to become overabundant in host.