Geology topics

D. R. Buhler

Publications and source records attributed to D. R. Buhler.

4 recordsLinked to original sources

USGS2002

Status and opportunities for genomics research with rainbow trout

The rainbow trout (Oncorhynchus mykiss) is one of the most widely studied of model fish species. Extensive basic biological information has been collected for this species, which because of their large size relative to other model fish species are particularly suitable for studies requiring ample quantities of specific cells and tissue types. Rainbow trout have been widely utilized for research in carcinogenesis, toxicology, comparative immunology, disease ecology, physiology and nutrition. They are distinctive in having evolved from a relatively recent tetraploid event, resulting in a high incidence of duplicated genes. Natural populations are available and have been well characterized for chromosomal, protein, molecular and quantitative genetic variation. Their ease of culture, and experimental and aquacultural significance has led to the development of clonal lines and the widespread application of transgenic technology to this species. Numerous microsatellites have been isolated and two relatively detailed genetic maps have been developed. Extensive sequencing of expressed sequence tags has begun and four BAC libraries have been developed. The development and analysis of additional genomic sequence data will provide distinctive opportunities to address problems in areas such as evolution of the immune system and duplicate genes. ?? 2002 Elsevier Science Inc. All rights reserved.

Conference Paper↗

USGS2001

Declining ring-necked pheasants in the Klamath Basin, California: II. Survival, productivity, and cover

Cover condition and its influence on nesting success, survival, and body condition of ring-necked pheasants (Phasianus colchicus) were evaluated at Tule Lake National Wildlife Refuge (TLNWR) and Lower Klamath National Wildlife Refuge (LKNWR). Inadequate nesting cover was responsible for extremely low nest success early in the nesting season at TLNWR. Later in the season at TLNWR, spring-planted crops provided cover to conceal nesting and renesting hens; however, only 0.07 young were produced (to 1 August) per hen during the study. The extremely low reproductive rates were well below those required to maintain a stable population. At TLNWR, most adult mortality during spring and early summer (before crops provided adequate cover) apparently resulted from predation by golden eagles (Aquila chrysaetos). This mortality occurred weeks before insecticide applications. Hard winters (cold temperatures and heavy snowfall) periodically reduce the pheasant population in the Klamath Basin and again greatly reduced numbers during the last year of this study. Unfortunately, pheasant populations declined under the conditions found during this study and were unable to recover from the hard winter of 1992 to 1993. Mean body mass and tarsal length of adult hen pheasants at TLNWR, which is intensively farmed, were less than those for hens at LKNWR, which is not intensively farmed. Results of our study suggest that TLNWR hens may have been nutritionally stressed, and that the amount and distribution of vegetative cover needs to be improved at TLNWR. Habitat management of edge cover along agricultural crops should feature perennial grasses and legumes with small tracts of land interspersed throughout the agricultural fields to provide alternative cover for wildlife in general including pheasants.

Northwestern Naturalist↗

USGS1998

Declining ring-necked pheasants in the Klamath Basin, California: I. Insecticide exposure

A study of organophosphorus (OP) insecticide exposure was conducted on a declining population of ring-necked pheasants (Phasianus colchicus) associated with agricultural lands at Tule Lake National Wildlife Refuge (TLNWR) during the summers of 1990–92. Findings at TLNWR were compared with a nearby pheasant population at Lower Klamath National Wildlife Refuge (LKNWR) not subjected to intensive farming or OP insecticide applications. Direct toxicity of anticholinesterase (antiChE) compounds (in this case methamidophos) killed 2 young pheasants (91 and 92% brain acetylcholinesterase [AChE] inhibition), but no deaths of adult radio-equipped hens were ascribed to direct insecticide intoxication. However, within 20 days postspray of OP insecticides, 68% (28 of 41) of the adult pheasants collected at TLNWR were exposed to antiChE insecticides, and exhibited brain AChE inhibition of 19–62%, with 15% (6 of 41) showing >55% brain AChE inhibition. The lack of radio-equipped hens dying was unexpected because >50% brain AChE inhibition has been frequently used as a ‘diagnostic tool’ for evaluating cause of death from antiChE insecticides. No young were radio-equipped, so the extent of the effects of insecticide exposure on the survivorship of young was unknown. It is concluded that insecticide exposure was not the major factor impacting the pheasant population (see Grove et al., in press), although some young were acutely intoxicated. However, the loss of insects killed by insecticide use may have contributed to food shortages of young pheasants, indirectly influencing survival.

California↗

USGS1961

Chemotherapy of hexamitiasis in fish

Heramita salmonis , the causative agent of hexamitiasis in salmonoid fishes, is endemic in most trout and salmon hatcheries throughout North America. The etiologic agent, a protozoan flagellate, ostensibly causes cellular damage in the caecal mucosa of afflicted fishes. It is also believed that heavy infections may interfere with normal growth by direct competition with the host for available nutrients in the intestinal tract. While the role of this supposed pathogen is relatively unclear, its presence in test fishes at this laboratory has caused considerable concern during the conduct of controlled nutritional studies. Although McNeil et al (1941) showed that the incidence of Hexamita infections is widespread, hexamitiasis appears to be commercially important only in turkeys (Almquist and Johnson, 1951) and fish (Davis, 1953). Very little has been reported on the protozoacidal effects of various drugs on the Hexamita infections in fish (Fish and McKernan, 1940; Smith and Quistorff, 1940; and Nelson, 1941). The most widely used chemotherapeutic agents are p-carbamidobenzene arsonic acid (carbarsone) and mild mercurous chloride (calomel). Initial attempts at this laboratory to control the parasite in infected fish populations using these two drugs at the recommended concentrations demonstrated that the former was erratic in effectiveness and the latter was toxic and produced loss in fish weight. The present study, therefore, was undertaken to find more effective therapeutic agents which would be palatable, non-toxic, and still effectively eradicate the protozoan from fish.

Journal of Parasitology↗