Effect of temperature on development and growth of the raptorial cladoceran Leptodora kindtii under laboratory conditions

1. Leptodora is a key species in many temperate freshwater systems, but so far its role in the food web could not be properly evaluated because detailed information about its secondary production was lacking. As we wanted to estimate the secondary production of Leptodora, we measured its development and growth rates in the laboratory. 2. Employing improved methods to estimate growth and instar durations, we cultured Leptodora kindtii in the laboratory at four constant temperatures (15, 17.5, 20 and 25 °C). Growth in length and development times of eggs and instar stages were assessed. 3. Growth rates at 15, 17.5 and 20 °C were similar, but at 25 °C growth was distinctly faster. At 17.5 °C we observed seven juvenile instar stages before the first adult instar stage was reached. [KEYWORDS: cladocera ; invertebrate predator ; laboratory culture pelagic ; zooplankton]

Effects of predation and food on the population dynamics of the raptorial cladoceran Leptodora kindtii

We assessed the trophic status of Leptodora kindtii in the food web of a shallow, eutrophic lake in which 0+ age group fish were the main predators. The mean biomass of 0+ fish during three successive years varied from 0.39 g dry wt m-2 in the first year to 0.05 g dry wt m-22 in the second year to 2.49 g dry wt m-2 in the third year. In the years with high fish biomass, densities of small-bodied (<1-mm) cladocerans (e.g., Bosmina spp., Chydorus sphaericus) were relatively high, whereas in the year with low fish biomass, densities of large-bodied Daphnia galeata were high, and densities of small-bodied cladocerans were lower. During the three study years, the predation pressure of juvenile fish and biomass and production of Leptodora were negatively correlated. Despite the low 0+ fish biomass in the second year, the Leptodora population densities were high only during the first part of the growing season. The elevated Leptodora mortality in July coincided with the lowest observed densities of smallbodied cladocerans, preferred prey items of Leptodora, and with an abundance of large-bodied Daphnia, the preferred food for 0+ fish. We conclude that the population dynamics of Leptodora during the growing season is predominantly regulated by direct predation effects.

Probability Integrals of the Multivariate "t" Distribution

Results on probability integrals of multivariate "t" distributions are reviewed. The results discussed include: Dunnett and Sobel's probability integrals, Gupta and Sobel's probability integrals, John's probability integrals, Amos and Bulgren's probability integrals, Steffens' non-central probabilities, Dutt's probability integrals, Amos' probability integral, Fujikoshi's probability integrals, probabilities of cone, probabilities of convex polyhedra, probabilities of linear inequalities, maximum probability content, and Monte Carlo evaluation. Copyright 2007 The Authors. Journal compilation (c) 2007 International Statistical Institute.