The biology of Schizomus vinei (Chelicerata: Schizomida) in the caves of Cape Range, Western Australia

The chelicerate order Schizomida is represented in Western Australia by a single species, Schizomus vinei Harvey, from caves in the semi–arid Cape Range on the North West Cape peninsula. Schizomus vinei occurs in eight of 170 caves known from the range but is found only in areas where the relative humidity exceeds 92%. The schizomids are associated with a rich fauna (at least 11 species) mostly of detritivores, some of which show troglobitic adaptations. They prey on the cave animals that feed on detritus and are known to eat oniscoid isopods, millipedes, cockroaches, worms and S. vinei.
The size class structure of the population in cave C 118 was strongly skewed negatively suggesting that the smaller size classes occupy interstices of the infill of sumps. Schizomids in this cave were found to be distributed at random up to the third nearest neighbour. The minimum population size, with 95% confidence, was estimated to be 1323 individuals. Schizomus vinei grew very slowly in vivaria. One female produced nine eggs which did not survive.
Schizomus vinei has a high mean rate of water loss (470–4 mg g^-1 h^-1) and a low resistance to water loss (15–2 cm sec^-1); their resistance is about 10 x greater than that of a free water surface, but is about two orders of magnitude lower than that of some spiders and scorpions. Schizomus vinei excretes a clear fluid and may be ammonotelic.
Allozyme electrophoresis strongly suggests that individuals from the different caves are of the same species. Consideration of climate, age of separation of the caves and the general biology of the schizomids suggests that those caves containing schizomids may be linked.