Some biological characteristics of rotifers and the effect of different salinities, foods and start densities on the development of rotifer populations [Một số đặc điểm sinh học của luân trùng và ảnh hưởng của độ mặn, thức ăn, mật độ giống ban đầu lên sự sinh trưởng quần thể luân trùng (Brachionus)]

Abstract

Studies on the biological characteristics of rotifers and the effects of various salinities, foods and starting densities on the growth of rotifer populations were performed in 1998 – 1999. The results showed that: + The mean size of cultured rotifers (Brachionus rotundiformis – Type S) in Khanhhoa was 173.33 21.45 m (S – Type). In the temperatures of 27 - 280C, the age at maturity was 18.13  1.76 hours; the interval between two spawning times was 3.93  0.53 hours; the total number of egg in one egg laying was 1-3 eggs; the total number of egg produced during one life cycle was 18.1  2.04 eggs; the length of the life cycle was 4.47  0.71 days. + The rotifer population developed best in salinities of 15 - 20ppt. + In the range of start densities from 5 to 30 inds/ml, higher start densities yielded, higher maximum densities. + The best food for rotifers was micro-algae, followed by yeast, mixture of micro-algae and yeast also gave the good result so this could be used to reduce the cost of rotifer production.