EFFECTS OF ALKALINITY AND PH ON THE SURVIVAL, GROWTH AND NEONATE PRODUCTION OF DAPHNIOPSIS TIBETANA SARS

Daphniopsis tibetana Sars (Crustacea :Cladocera :Daphniidae)is a low-medium saline lake cladoceran showing wide but patchy distribution in plateau saline lake in Asia.In China, D.tibetana widely distributes in saline waters in Tibet, Qinghai province and Xinjiang province.In the present paper, D.tibetana were collected from Lake Namuka Co.The animals can live in diluted seawater via acclimatization.Effects of alkalinity and pH on the survival, growth and neonate production of D.tibetana Sars were studied under 16 ±0.5 ℃and S =15.5 ±0.5.The results showed that 24h LC50 of pH on D.tibetana were 4.18 and 10.84, and 48h LC50 of pH on it were 4.37 and 10.71 ;24h LC50 and 48h LC50 of alkalinity on D.tibetana were 529.43mmol/L and 503.69mmol/L, respectively.When D.tibetana was reared at pH 7 -8, growth and survival rate were significantly higher than those were reared at other groups.When D.tibetana was reared at pH7, intrinsic rate of increase (rm)was 0.3014/d, which was the highest of all tested groups.When at pH8, rm was 0.2924/d.Survival rates and growth rate of D.tibetana who reared at ALK =4.75 -18.9 mmol/L did not significantly differ.When alkalinity was 11.9 mmol/L, age at first production (d)was 18.70 ±0.65 d, which was lower than other groups.The rate of egg production of D.tibetana who were reared 11.9 and 18.9 mmol/L of alkalinity were 1.1671 and 1.1877, which were higher than those were reared at other groups.When D.tibetana was reared at 7.54 mmol/L of alkalinity, rm was 0.3425/d, which was the highest of all tested groups.At other tested groups, rm of D.tibetana were 0.2889 -0.3425/d.In terms of results, optimal pH and alkalinity of survival of D.tibetana were 7 -8 and 4.75 -18.9mmol/L, respectively