Changes in growth and size of Keratella cochlearis (Gosse) in relation to some environmental factors in cultures

Keratella cochlearis (Gosse) was cultured non-axenically in Carefoot medium diluted with Erken water at 5 °C, 15 °C and 20 °C with Rhodomonas minuta (Skuja) as a food alga. The rotifer reached ca. 120 ind. ml^?1, having generation times of 2–7 days, a Q₁₀-value of ca. 2, and at the lowest temperature >20% longer posterior spines. When co-cultured with Chlorella sp., at 0–30 mg Ca l^?1 and 1.6 meq NaHCO₃ l^?1 in medium L 11 at 20 °C, the maximum generation time and individual numbers were 3–4 days and up to 100 ind. ml^?1, respectively. Animal numbers increased in relation to nutrient multiples, up to two multiples, of the culture medium L 16. Growth and length were reduced, although the width increased above two multiples of this culture medium. The trace metal tolerance was broad and increased additions of a metal mixture (L 11) slightly increased the length of the rotifers. No major changes in the length were observed when HCO₃ or Ca were varied in the culture medium (L 11), although a decrease in the length was noted in old cultures.