Geology topics

T. Craig Robinson

Publications and source records attributed to T. Craig Robinson.

4 recordsLinked to original sources

USGS2011

Olfactory sensitivity of Pacific Lampreys to lamprey bile acids

Pacific lampreys Lampetra tridentata are in decline throughout much of their historical range in the Columbia River basin. In support of restoration efforts, we tested whether larval and adult lamprey bile acids serve as migratory and spawning pheromones in adult Pacific lampreys, as they do in sea lampreys Petromyzon marinus . The olfactory sensitivity of adult Pacific lampreys to lamprey bile acids was measured by electro-olfactogram recording from the time of their capture in the spring until their spawning in June of the following year. As controls, we tested L-arginine and a non-lamprey bile acid, taurolithocholic acid 3-sulfate (TLS). Migrating adult Pacific lampreys were highly sensitive to petromyzonol sulfate (a component of the sea lamprey migratory pheromone) and 3-keto petromyzonol sulfate (a component of the sea lamprey sex pheromone) when first captured. This sensitivity persisted throughout their long migratory and overwinter holding period before declining to nearly unmeasurable levels by the time of spawning. The absolute magnitudes of adult Pacific lamprey responses to lamprey bile acids were smaller than those of the sea lamprey, and unlike the sea lamprey, the Pacific lamprey did not appear to detect TLS. No sexual dimorphism was noted in olfactory sensitivity. Thus, Pacific lampreys are broadly similar to sea lampreys in showing sensitivity to the major lamprey bile acids but apparently differ in having a longer period of sensitivity to those acids. The potential utility of bile acid-like pheromones in the restoration of Pacific lampreys warrants their further investigation in this species.

Oregon, Washington↗

USGS2006

Comparison of synthesis of 15α-hydroxylated steroids in males of four North American lamprey species

Recent studies have provided evidence that 15α-hydroxytestosterone (15α-T) and 15α-hydroxyprogesterone (15α-P) are produced in vitro and in vivo in adult male sea lampreys ( Petromyzon marinus ), and that circulatory levels increase in response to injections with gonadotropin-releasing hormone ( GnRH ). We examined four species from the Petromyzontidae family including silver lampreys ( Ichthyomyzon unicuspis ), chestnut lampreys ( I. castaneus ), American brook lampreys ( Lethenteron appendix ), and Pacific lampreys ( Entosphenus tridentatus ) to determine if these unusual steroids were unique to sea lampreys or a common feature in lamprey species. In vitro production was examined through incubations of testis with tritiated precursors, and 15α-T and 15α-P production was confirmed in all species through co-elution with standards on both high performance liquid chromatography ( HPLC ) and thin layer chromatography . In vivo production was proven by demonstrating that HPLC-fractionated plasma had peaks of immunoreactive 15α-T and 15α-P that co-eluted with standards through using previously developed radioimmunoassays for 15α-T and 15α-P. The possible functionality of 15α-T and 15α-P was further examined in silver and Pacific lampreys by investigating the effect of injection of either type of lamprey GnRH on plasma concentrations of 15α-T and 15α-P. Injections with exogenous GnRH did not affect circulatory levels of either steroid in silver lampreys, and only GnRH III elicited higher levels of both steroids in Pacific lampreys. The 15α-hydroxylase enzyme(s) for steroids appeared to present in adult males of all species examined, but the question of whether 15α-hydroxylated steroids are functional in these lamprey species, and the significance of the 15- hydroxyl group, requires further research.

General and Comparative Endocrinology↗

USGS2004

Distribution and relative abundance of fishes in littoral areas of Chief Joseph Reservoir, Columbia River

We surveyed fish assemblages in littoral areas of Chief Joseph Reservoir of the upper Columbia River to aid in understanding this ecosystem. Fish distributions and abundances were examined during April-July 1999 in relation to environmental conditions in the reservoir. We also compared the fish assemblages in Chief Joseph reservoir in 1999 to a past study conducted during 1974-1975, and to assemblages in other areas of the Columbia River. During 67 hr of electrofishing and 78 beach seine hauls in Chief Joseph Reservoir, 7460 fishes representing 8 families were collected. The majority of the catch was native – northern pikeminnow; redside shiners; longnose, bridgelip, and largescale suckers; and sculpins. The most abundant introduced species was walleye, and one species, rainbow trout, was mostly of net-pen origin. Larger sizes of suckers and northern pikeminnow were most abundant in the upper reservoir, likely due to upstream spawning migrations. The lower reservoir contained greater abundances of smaller fishes, and this area had lower flows, smaller substrates, and more complex shorelines that offered these fishes refugia. Only adult suckers displayed significant differences in abundances related to substrate. The relative abundances of species appeared to have changed since the 1970s, when the dominant fishes were northern pikeminnow, peamouth, largescale suckers, and walleye. Fish assemblage differences between Chief Joseph Reservoir and lower Columbia River reservoirs were also evident due to the morphology of the reservoir, its more northerly location, and the lack of fish passage facilities at Chief Joseph Dam. Our study is one of the few descriptions of fishes in the upper Columbia Rivers.

Washington↗

USGS2000

Gonadotropin-Releasing hormones in the brain and pituitary of the white sucker

The present study investigated GnRH forms within the brain of a representative of the order Cypriniformes, the white sucker, Catostomus commersoni, using HPLC, RIA, and immunocytochemistry . Several immunoreactive (ir) GnRH forms were identified in the brain of the white sucker by chromatography and radioimmunoassay , including ir-salmon GnRH, ir-lamprey GnRH-I and -III, and ir-chicken GnRH-II. Results from immunocytochemical studies were consistent with multiple GnRH forms distributed in different patterns, particularly for fibers. Neuronal perikarya containing ir-salmon GnRH and ir-lamprey-like GnRH were found laterally within the preoptic area and rostral hypothalamus . Cells containing exclusively ir-salmon GnRH appeared slightly more rostrally, but in the same region. Fibers containing ir-salmon GnRH and ir-lamprey-like GnRH were seen throughout the caudal telencephalon and extended into the diencephalon , toward the pituitary . Fibers containing ir-chicken-II-like GnRH were also seen in the caudal telencephalon, but were concentrated more dorsally in the diencephalon. Within the pituitary, fibers containing ir-salmon GnRH and ir-lamprey-like GnRH entered the neurohypophysis , but differed in their destinations. Fibers containing ir-salmon GnRH remained within the neurohypophysis, while fibers containing ir-lamprey-like GnRH targeted adenohypophyseal tissue. These findings are consistent with the hypothesis that multiple GnRH forms with multiple functions exist within the brain and pituitary of teleosts and provide further evidence of a lamprey-like GnRH within an early evolved teleost species.

General and Comparative Endocrinology↗