Two new genera and two new species of the mite family Neopygmephoridae (Acari: Heterostigmata) associated with small mammals from USA

Two new monotypic genera and two new species of the mite family Neopygmephoridae (Acari: Pygmephoroidea) associated with small mammals are described from USA: Crossdania gen. nov. with the type species Crossdania tubulosa sp. nov. associated with Northern grasshopper mouse, Onychomys leucogaster (Rodentia: Cricetidae) and Great Basin pocket mouse, Perognathus parvus (Rodentia: Heteromyidae), and Theriodania gen. nov. with the type species Theriodania venusta sp. nov. associated with Merriam's kangaroo rat, Dipodomys merriami (Rodentia: Heteromyidae).

Prevalence of cutaneous evaporation in Merriam's kangaroo rat and its adaptive variation at the subspecific level

Previous estimates suggested that ventilatory evaporation constitutes the major source of water loss in kangaroo rats (Dipodomys spp.). We quantified rates of water loss in Merriam's kangaroo rat (Dipodomys merriami) and demonstrate the degree to which acclimation to a particular thermal and hydric environment plays a role in the intraspecific variation in water loss evident in this species. We draw the following conclusions: (1) that water loss varies intraspecifically in Merriam's kangaroo rat, in association with habitats of contrasting aridity and temperature; (2) that animals from more xeric locations have lower water loss rates than those from more mesic sites; (3) that most water loss is cutaneous, with ventilatory evaporative water loss contributing, at most, only 44% to total evaporative water loss; and (4) that intraspecific differences in rates of water loss are not acclimatory, but fixed. After acclimating under the same conditions, xeric-site animals still show a 33% lower rate of evaporative water loss than mesic-site animals.