title: Growth of two Pisidium (Bivalvia, Sphaeriidae) species in the laboratory.
abstract: Growth of Pisidium casertanum and P. subtruncatum from the profundal of the eutrophic Lake Esrom was followed at four temperatures in the laboratory. The growth rate of both species increased with increasing temperature, but the maximum in P. casertanum was attained at 12° C, instead of at 20° C as in P. subtruncatum. The variation of Q10of growth in relation to animal weight was of similar form in both species at higher temperatures (6-12°C) but opposite at low temperatures (2-6°C). In the latter case Q10of P. casertanum had a peak and that of P. subtruncatum a low value at a corresponding size preceding maturity. At constant temperatures growth curves of the form y=a+bx+cx2were obtained, where y is weight in μg and x is time in days. The growth of both species under natural conditions was simulated by use of the experimental growth rate equation and natural birth periods, sizes at birth, and temperature cycles. These simulations gave a maximum life span of 2.5-3 years for P. casertanum and 3.5-4.5 years for P. subtruncatum. The latter species showed slower growth rates at the low or medium temperatures prevailing in the profundal of this lake. A comparison with growth in nature reveals that the simulation overestimated growth in case of P. casertanum.
authors.affiliation: Freshwater-Biological Laboratory, University of Copenhagen, 51 Helsingørsgade, DK-3400, Hillerød, Denmark.
authors.forename: Ismo J
authors.initials: IJ
authors.lastname: Holopainen