Search results for "river lamprey"
showing 3 items of 3 documents
Selection of spawning substratum by European river lampreys (Lampetra fluviatilis) in experimental tanks
2014
The selection of spawning substratum by the river lamprey (Lampetra fluviatilis) was studied in two experimental tanks with different flow conditions. In both tanks, four gravel sizes mixed with 15% sand were available to the test animals. In the tank with the lower current speed, lampreys selected in favour of the finest (2–8 mm) gravel size available against gravel sizes 4–20 mm and 8–40 mm. Selection was also significantly different in the tank with higher current speed where selection against the medium-sized substratum (4–20 mm) was evident, but there were no differences between selection for gravel sizes 2–8 mm, 2–40 mm and 8–40 mm relative to availability. Substratum selection and ob…
Migratory behaviour and holding habitats of adult river lampreys (Lampetra fluviatilis) in two Finnish rivers
2015
The effect of environmental factors on migratory activity of adult river lampreys entering the Kalajoki and Perhonjoki, rivers in Finland, for spawning was studied using correlation and regression analyses. Telemetric tracking of 60 individuals was utilized to study the migratory patterns and holding habitat requirements of adult river lampreys. The increases in the river discharge, wind forcing towards the river mouth and speed and magnitude of river water cooling had positive effects on the numbers of lampreys entering the rivers whereas the increase in the illumination intensity of the moon had a negative effect on their migration activity. Radio-tagged lampreys typically passed slow-flo…
Vitellogenin from female and estradiol-stimulated male river lampreys (Lampetra fluviatilis L.)
2001
The influence of estradiol-17β (E2) on vitellogenesis is well documented for a number of oviparous craniates. We have examined the role that estradiol-17β plays in the induction and regulation of vitellogenin synthesis in the maturing European river lamprey, Lampetra fluviatilis. In both females and males the estradiol-17β concentrations in the plasma reached comparable maximum values in March, only a few weeks before spawning. Throughout the spawning run, the vitellogenin titer in the blood of females remains rather constant while the ovary volume increases. In contrast, we never found circulating VTG in untreated male lampreys. The synthesis and secretion of the yolk precursor molecule ca…