Local climate aridity influences the distribution of thelastomatoid nematodes of the Australian giant burrowing cockroach

Abstract

SUMMARYIn this study, we examined the effects of local climate aridity on the richness and composition of the thelastomatoid (Nematoda: Oxyurida) guild parasitizing the Australian giant burrowing cockroach, Macropanesthia rhinoceros (Blattodea: Geoscapheinae). In total, 9 thelastomatoid species parasitized this cockroach in north-eastern Australia (Queensland). Local observed richness ranged from 3 species (in Cooktown, Magnetic Island, Maiden Springs and Whitsunday Island) to 7 species (in Rochford Scrub). The lowest richness occurred in both relatively wet and dry climates, and the highest richness was in moderate climates. Three species, Cordonicola gibsoni, Leidynemella fusiformis and Travassosinema jaidenae, were found at all 13 collection sites. One species, Geoscaphenema megaovum, was found exclusively in dry to moderate climates. The remaining species, Blattophila sphaerolaima, Coronostoma australiae, Desmicola ornata, Hammerschmidtiella hochi and Jaidenema rhinoceratum, were found in moderate climates only. We hypothesize that the egg is the stage in the thelastomatoid life-cycle most vulnerable to the effects of adverse climate and that the geographical distribution for each species is, in part, bound by environments that are too dry, resulting in egg desiccation, and by environments that are too wet, resulting in decreased oxygen uptake across the egg-shell and in osmotic lysing.