Studies on comparative population growth of some species of the rotifer Lecane (Rotifera).

We compared the population growth patterns of 5 species of the rotifer genus Lecane [(L. quadridentata (Ehrenberg, 1830), L. cornuta (Muller, 1786), L. papuana (Murray, 1913), L. unguitata (Fadeev, 1925) and L. pyriformis (Daday, 1905)] ranging in adult average body size from 30 to 140 Lm. All species were cultured under laboratory conditions for 25-30 days using the green alga Scenedesmus acutus as the exclusive diet, at a density of 1.0 X 106 cells ml-1 at 24oC. Regardless of the species, lecanids reached their peak population densities after 4 weeks. Peak population densities ranged from 15 to 320 ind. ml-1, depending on body size. There was an inverse curvilinear relation between body lengths and peak population abundances (densities) of the Lecane species. Egg ratios (eggs per female) for the tested species were <0.6 during the exponential phase but declined to 0.1 (or lower) as the population density increased. The rates of population increase for the lecanids were in general lower (0.10 to 0.21 day-1) than other well-studied rotifer species including members of Brachionidae.