Ref ID : 7504
Frode Thorhauge; Growth and life cycle of Potamothrix hammoniensis (Tubificidae, Oligochaeta) in the profundal of eutrophic Lake Esrom. A field and laboratory study. Arch.Hydrobiol. 78(1):71-85, 1976
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In the deep profundal of Lake Esrom, Denmark, growth of Potamothrix hammoniensis was most rapid in spring and autumn, and negative at low oxygen concentrations during late summer. Growth still occurred at 2 degrees C, but its rate decreased at low temperatures. A late autumn turn-over resulted in a new generation of low average weight, and in breeding individuals of a high mean weight in the following summer. The occurrence of these latter was associated with decreased predation. High densities of Chironomus anthracinus larvae decreased, but could not prevent, growth and reproduction of P. hammoniensis. The 1956 generation bred first at four years old at 20 m depth, but at two or three years old at 11 m. At shallower depths the annual number of degree days was higher and the period with very low oxygen concentrations, if occurring, of only short duration.