Possible influence of B chromosomes on the prevalence and abundance of intestinal nematode parasites of the yellow-necked mouse (Apodemus flavicollis)

Abstract

Background. B chromosomes are supernumerary chromosomes that have been discovered in over 1000 eukaryote species. They show remarkable variaton in structure and behaviour, their only common trait being their conditonal dispensability. The influence of these genetc elements on their carriers is stll debated, with the two most accepted models of their maintenance being the parasitc and the heterotc model. Objectves. The purpose of this study was to investgate the possible influence of B chromosomes on quanttatve characteristcs of intestnal nematode infecton in the yellow-necked mouse (Apodemus flavicollis). Material and Methods. A total of 305 mice were sampled across 18 localites on the territory of Serbia over five years. Every individual with more than 48 chromosomes was considered to have Bs. Afer dissecton, intestnal nematodes were extracted and identfed. An analysis of Bs influence on parasite prevalence and abundance was conducted, using the exact unconditonal test and generalized linear modelling respectvely. Results. Nine intestnal nematode species were detected in the host sample. In the total host sample, both prevalence and abundance of intestnal nematodes were greater in Bs carriers. Two nematode species, Aspiculuris tetraptera and Mastophorus muris, had signifcantly higher prevalence in the B+ subset of the host sample. Similarly, B chromosomes explained a signifcant proporton of abundance variaton of the nematode species Syphacia frederici, with its abundance greater in Bs carriers. Conclusion. While the results of this study show a possible connecton between Bs presence and higher prevalence and abundance of intestnal nematodes, this fnding is purely correlatonal. Previously published data indicate a complex effect of B chromosomes on host characteristcs and survival through various molecular pathways. Bs carriers may reap the benefts of increased survival prospects as a by-product of the selfsh behaviour of the chromosomes themselves, blurring the line between the parasitc and heterotc model.