Ion movements in the nervous system of the American cockroach,periplaneta Americana (L.), influenced by toxaphene

Abstract

The effect of toxaphene upon ion fluxes of the central nervous system (CNS) of the cockroach, Periplaneta americana (L.), was studied in vitro. The CNS, divided into three sections (brain, thoracic, and abdominal), was exposed to 10 M toxaphene in saline containing ²⁴Na⁺, ⁴²K⁺, ³⁶Cl^‐, or ⁴⁵Ca⁺⁺. Uptake and efflux of these ions were evaluated. Toxaphene was responsible for significant increases in the internal levels of ⁴²K⁺ and ⁴⁵Ca⁺⁺, but had little affect upon Na or ³⁶Cl^‐ movements. The resulting concentration changes of the ions may be involved in the neural activity observed with toxaphene poisoning. Of the three CNS sections, significant changes were more numerous and occurred earlier in abdominal sections.     

Darwin's Fox: A Distinct Endangered Species in a Vanishing Habitat

The temperate rain forest of Chiloé Island, Chile, is inhabited by an endemic fox ( Dusicyon fulvipes ) first described by Charles Darwin and now designated Darwin's fox. Despite morphological differences, Darwin's fox has been considered only an insular subspecies of the mainland chilla fox ( D. griseus ). This follows the assumption that the island population, with an estimated population of less than 500, has been separated from the mainland chilla fox for only about 15,000 years and may have received occasional immigrants from the mainland. Consequently, this island population has not been protected as endangered or bred in captivity. Recently, a population of Darwin's fox was discovered on the Chilean mainland 600 km north of Chiloé Island. This population exists in sympatry with chilla and possibly culpeo ( D. culpaeus ) foxes, which suggests that Darwin's fox may be reproductively isolated. To clarify the phylogenetic position of Darwin's fox, we analyzed 344 bp of mitochondrial DNA control-region sequence of the three species of Chilean foxes. Darwin's foxes from the island and mainland populations compose a monophyletic group distinct from the two other Chilean fox species. This indicates that Darwin's fox was probably an early inhabitant of central Chile, and that its present distribution on the mainland may be a relict of a once much wider distribution. Our results highlight the ability of molecular genetic techniques to uncover historical relationships masked by recent events, such as local extinctions. The "rediscovery" of Darwin's fox as a distinct species implies that greater significance should be given to the protection of this species and its unique habitat and to documenting the extent of its mainland distribution.     

Radionuclide content of Las Vegas Wash sediments

The Las Vegas Wash is an excavated waterway channel which drains all surface water and effluent discharge from sewage-treatment facilitates from the greater Las Vegas Metropolitan Area to Lake Mead. Fine and course sediment samples were collected at 100-m intervals and analyzed to determine the distribution of gamma-emitting radionuclides in the lower 5,500 m of the Las Vegas Wash. Results indicate depletion of long-lived fission products in upstream Wash sediments. However, trace levels of ¹³⁷Cs measured in downstream sediments suggest the resuspension and transport of radioactive fallout within the Wash. Levels of ⁴⁰K, ²³²Th, ²³⁵U, and ²³⁸U found in Wash sediments were consistent with levels typically found in southeast Nevada soils.