Biodiversity of the parasite fauna of the rodent genera Zyzomys Thomas, 1909 and Pseudomys Gray, 1932 from northern Australia

This study of the parasite fauna of five Australian rodents (Muridae: Hydromyinae: Conilurini) was undertaken to increase the knowledge of Australian parasite biodiversity. Trapping for Zyzomys argurus (Thomas, 1889), Pseudomys delicatulus (Gould, 1842), P. desertor Troughton, 1932, P. gracilicaudatus (Gould, 1845) and P. hermannsburgensis (Waite, 1896) (Rodentia: Muridae) was carried out at 16 locations in Queensland between 2004 to 2006. A total of 51 rats were captured and examined for parasites. In addition, 119 rats, from collections in the Queensland Museum and the University of Sydney, were examined. Finally, 57 samples of parasites collected from the above hosts and deposited at the Australian National Wildlife Collection (CSIRO) were identified. From these five rodent species, 15 species of ectoparasites and 17 species of endoparasites were recorded. Fifteen new host records and 14 new locality records were found. The ectoparasites comprised four species of Laelaps Koch, 1836 (Parasitiformes: Laelapidae), four species of chiggers (Acariformes: Trombiculidae), two species of fleas (Siphonaptera: Pulicidae, Pygiospyllidae) and two species of ticks (Parasitiformes: Ixodidae). Three new species of lice (Anoplura: Hoplopleuridae) were discovered. The 17 endoparasites, all helminths, comprised fourteen species of nematode and three species of cestode. There were 11 species of oxyurids (Nematoda: Oxyuridae, Heteroxynematidae), including 10 new species of Syphacia, two species of Odilia (Nematoda: Heligmonellidae), and one species of Nippostrongylus (Nematoda: Heligmonellidae). Three species of cestodes (Cestoda: Anoplocephalidae, Taeniidae, Davaineidae) were collected. There were no trematodes or acanthocephalans found in any of the rodents examined. No protistan parasites were found in tissue and blood samples taken from the rodents. The mean species diversity of parasites for each host rodent species was consistently low, with values of Simpsons Reciprocal Index ranging from 1.00 1.53. Possible factors contributing to this low diversity include habitat preferences, dietary ecology and social structure. There was no significant relationship found between host body weight and abundance of ectoparasites, or host body weight and species richness of helminths. The index of discrepancy (D) was used to evaluate the distribution of parasite species across host populations. Most parasites were found to have aggregated distributions within the host populations. The exception to this was two of the four species of laelapid mite, with values <5, indicating that they were common across host populations. The phylogenetic relationships of the Syphacia species occurring in the Australian bioregion were investigated using morphological characters. Relatively low resolution of the trees produced indicated that there may be a high degree of similarity between species. Two main clades were identified- a clade of genera of Syphaciini from Borneo was shown to be basal to the clade of species of Syphacia examined. Within the clade of the genus Syphacia, the new species identified in this study formed a single cluster on trees. There was no evidence, however, for strict coevolution of these worms and their hosts. Overall, the research presented here adds considerable knowledge to the previous paucity of information of the parasites of Australian native rodent species. This was achieved by contributing new host records, locality records and identifying and describing several new species. The relationships between conilurin rodents and their parasites suggests that coevolution plays a large part in the speciation of parasites, and that minimal host switching has occurred in the helminths of the conilurins of northern Australia.