THE REPRODUCTION AND GROWTH PATTERN OF LARVAE OF BELLAMYA AERUGINOSA CULTURED IN RICE FIELD

Bellamya is an important freshwater snail, which widely distributes in different lakes. It has high nutritional value and is the main source of famous food, Liuzhou River snails rice noodle, and it had been mainly captured from the lake distributing in basin of the Yangtze River. With the implement of 10-year Fishing Ban on Yangtze River, the supply of wild Bellamya will be shut down. So, artificial culture become urgent and necessary. In order to supply Bellamya for Liuzhou River snails rice noodle, we carried out the experiment of reproduction and larval B. aeruginosa growth in rice field. The adult B. aeruginosa was captured from the lake in Hubei Province and transported to Liuzhou by truck in April, 2019. Then it was cultured in rice field with 667 m² area in Liuzhuo, Guangxi Zhuang Autonomous Region. It was cultured 150 kg in each field. B. aeruginosa was fed with compound feed, and was sampled in 0.25 m² area each month from May to November in 2019. The reproductive pattern and the brood amount were calculated. Meanwhile, the shell height, shell width, shell mouth width and body weight of larval B. aeruginosa were measured. The fitting equations and the growth equation were calculated. The main results were as follows: In rice field, the reproductive peak period of B. aeruginosa was in June. The reproductive cycle was 2 months during the reproductive period. The minimum body weight of reproductive individual was 0.9 g, and the minimum age of reproduction individual was 2 months. This result was similar to the results from the natural ecological group. The brood amount were significantly difference in different body weight groups, except in 1.00 g to 3.99 g groups, which were significantly related to body weight, and the heavier individual had the more brood mount. About the growth pattern, the rapid growth period of larval B. aeruginosa were June and July, then it is increased slowly from August. The relative growth rate of shell height were 47.95% and 36.99% in June and July, and the relative growth rate of body weight were 180.60% and 128.43% in June and July, respectively. This kind of growth pattern was similar to other aquatic organisms. In rice field, there were positive linear relationship between shell width/shell mouth width and shell height, and positive power regression between shell height and body weight. The fitting equations of the shell height and body weight of larval B. aeruginosa was W=0.0005 H^2.785. Using three different growth equations, i.e. Bertallanffy, Logistic, and Gompertz, fit the growth model between shell height and the growth time, and body weight and the growth time. All three growth equations were fitting good. The expression of shell height growth equation of larval B. aeruginosa in rice field was H_t=19.368/(1+3.608e^–1.056t). The height of inflection point was 9.684 mm, and the age of inflection point was 1.215 months. The maximum monthly increase was 5.113 mm. The expression of body weight growth equation was W_t=2.012e^{–5.051exp (–0.753t)}, and the inflection point weight was 0.740 g. The inflection point month age was 2.151 months, and the maximum monthly gain was 0.557 g. The growth of shell height and body weight showed allometric growth because the allometric growth factor b was 2.785 (b<3). According to our results, the reproductive peak period of B. aeruginosa was in June in rice field. The minimum age of reproduction individual was 2 months. The rapid growth period of larval B. aeruginosa was from June to July.