Functional and evolutionary implications of the cellular composition of the gill epithelium of feeding adults of a freshwater parasitic species of lamprey,Ichthyomyzon unicuspis

This paper provides the first description of the cellular composition of the gill epithelium of feeding adults of Ichthyomyzon unicuspis Hubbs and Trautman, 1937 (silver lamprey), a parasitic species of lamprey that is confined to fresh water. The surface layer of this epithelium consists solely of pavement cells and intercalated mitochondria-rich cells, which are the only cell types found in all freshwater stages of lampreys and thus considered responsible for the uptake of Na+ and Cl- in hypotonic environments. This epithelium does not contain, however, the chloride cells present during the marine parasitic phase of anadromous lamprey species, such as Petromyzon marinus L., 1758 (sea lamprey), and which are responsible for secreting excess Na+ and Cl-. The absence of this cell type in parasitic adults of I. unicuspis also differs from its presence in parasitic adults of landlocked P. marinus and metamorphosing individuals of the exclusively freshwater nonparasitic species Lethenteron appendix (DeKay, 1842) (American brook lamprey), and which thus reflects the retention of a cell type that was crucial for osmoregulation during the marine phase of their respective anadromous parasitic ancestors. The absence of chloride cells in I. unicuspis is consistent with the hypothesis that Ichthyomyzon, which is at or close to the base of the phylogenetic tree for Northern Hemisphere lampreys (Petromyzontidae), evolved in fresh water or has been confined to fresh water for a very long period

Hydroxyl radical consumption following photolysis of vapor-phase hydrogen peroxide at 266 nm: Implications for photofragmentation laser-induced fluorescence measurements of hydrogen peroxide

The decay of OH concentration following photolysis of room-temperature vapor-phase hydrogen peroxide is studied as a function of photolysis fluence at 266 nm in an open air environment. The rate of decay is found to increase with increasing photolysis fluence, i.e., with increasing number of photodissociated H2O2(g) molecules. Single-exponential functions approximate the OH concentration decay rather well, even for higher photolysis levels, and the decay time is shown to be inversely proportional to the H2O2(g) concentration. For fluences of about 450 mJ/cm(2) the difference between a single-exponential decay and measured data is becoming evident after approximately 150 mu s. Calculations based on a chemical kinetics model agree well with experimental data also for times > 150 mu s. By combining the model with measurements, the actual photolysis levels used in experiments are estimated. The best fit between measured data and the model suggests that about 1.1% of the H2O2(g) molecules are dissociated with a photolysis fluence of similar to 450 mJ/cm(2), in reasonable agreement with a Beer-Lambert based estimation. Excitation scans did not unfold any differences between OH spectra recorded at different photolysis fluences

Evaluating Genetic Structure Among Resident and Migratory Forms of Bull Trout (Salvelinus Confluentus) in Northeast Oregon

Many salmonids express multiple behavioural forms within the same population, representing an evolutionary adaptation to a heterogeneous environment. For bull trout, resident and migratory forms co-occur in streams, but it is unknown whether the two forms assortatively mate. We assessed genetic differentiation between resident and migratory bull trout (using eight microsatellite loci) in the South Fork Walla Walla River. We PIT-tagged and fin-clipped bull trout and assigned individuals to behavioural subpopulations based on movement patterns. The pair-wise FST value between resident and migratory subpopulations (0.0037) was statistically insignificant, and individual-based analyses of structure using both multivariate and Bayesian approaches showed a lack of genetic structure within the population. These results have important implications for assessing population status and management; while the population may be managed as a single reproductive unit, the phenotypic variation within this population may have fitness consequences and thus merits conservation