Inter and intra-population phenotypic and genotypic structuring in the European whitefish Coregonus lavaretus, a rare freshwater fish in Scotland.

This study revealed between-lake genetic structuring between Coregonus lavaretus collected from the only two native populations of this species in Scotland, U.K. (Lochs Eck and Lomond) evidenced by the existence of private alleles (12 in Lomond and four in Eck) and significant genetic differentiation (FST = 0·056) across 10 microsatellite markers.

Are phenotypic traits useful for differentiating among a priori Coregonus taxa?

A key for three putative species apparently found in three geographic areas, i.e. Coregonus clupeoides (in Scotland), Coregonus stigmaticus (in England), and Coregonus pennantii (in Wales) given in a recent review was tested quantitatively using 544 individuals from nine populations.

Has habitat heterogeneity promoted phenotypic and ecological sub-structuring among a Coregonus lavaretus population in a large Scottish lake?

Differences in stable-isotope values, morphology and ecology in whitefish Coregonus lavaretus were investigated between the three basins of Loch Lomond. The results are discussed with reference to a genetic investigation to elucidate any substructuring or spawning site fidelity. Foraging fidelity between basins of Loch Lomond was indicated by δ¹³C and δ¹⁵N values of C.

The effect of lens depression on the components of outflow resistance.

The effect of lens depression on resistance to flow through the inner wall of Schlemm's canal, circumferentially along the canal, and through the collector channels was measured in enucleated eyes. In one series of experiments the anterior chamber was perfused while canal pressure was monitored, thus allowing us to estimate inner wall resistance and a combination of canal plus collector-channel resistance. In a second series of experiments the inner canal wall was blocked with oil while the canal was perfused, allowing us to measure both circumferential flow resistance and collector-channel resistance.

Schlemm's canal: the effect of intraocular pressure.

We have shown that in the excised eye when oil in the anterior chamber has made the trabecular mesh impermeable, resistance to circumferential flow along the canal increases moderately as transmural pressure is increased. At the same time, resistance to outflow from the canal through the collector channels increases markedly as transmural pressure is increased from low levels to 35 or 40 mm Hg. We have suggested that the usual primary defect in open-angle glaucoma is reduced facility of the inner canal wall and that collapse of the canal with reduction of filtering area and plugging of collector channels is a secondary effect.