匙吻鲟仔稚鱼摄食前后生长规律与体脂肪酸组成研究

Growth Regulation and Fatty Acid Composition of Larval and Juvenile Chinese Paddlefish Before and After Feeding a Diet

为了掌握匙吻鲟(Polyodon spathula)仔稚鱼摄食前后的生长规律及其能量代谢情况,研究了孵化后第3、5、7、13、19、25天匙吻鲟仔稚鱼生长特征与体脂肪酸组成变化。结果表明,摄食前匙吻鲟仔鱼全长(L_1)生长方程为:L_1=0.1288t_1+0.7134(3≤t_1≤7),R^2=0.9993;摄食后匙吻鲟仔稚鱼全长(L_2)生长方程为:L_2=0.9133e^(0.0785t_2)(7<t_2≤25),R^2=0.9913;2个阶段全长(L)生长方程为:L=0.8948e^(0.0796t)(3≤t≤25),R^2=0.9950。摄食前匙吻鲟仔鱼体重(W_1)生长方程为:W_1=0.0035t_1-0.0032(3≤t_1≤7),R^2=0.9932;摄食后仔稚鱼体重(W_2)生长方程为:W_2=0.0061e^(0.1893t_2)(7<t_2≤25),R^2=0.9948;2个阶段体重(W)生长方程为:W=0.0049 e^(0.2004t)(3≤t≤25),R^2=0.9911。2个阶段匙吻鲟仔稚鱼体重(W)与全长(L)的幂函数关系为:W=0.007L^(2.513)。前仔鱼期,随着孵化天数的增加,匙吻鲟饱和脂肪酸(SFA)比例显著升高(P<0.05);单不饱和脂肪酸(MUFA)比例显著下降(P<0.05);多不饱和脂肪酸(PUFA)比例无显著变化;其中,亚油酸(C_(18)∶2 n-6)、α-亚麻酸(C_(18)∶3 n-3)、n-6 PUFA比例显著下降(P<0.05),EPA(C_(20)∶5 n-3)、DHA(C_(22)∶6 n-3)、n-3 PUFA比例显著升高(P<0.05);摄食生物饵料后,随着孵化天数的增加,匙吻鲟SFA比例先升高后下降(P<0.05);MUFA比例先下降后升高再下降(P<0.05);PUFA比例先升高后下降再升高(P<0.05);其中C_(18)∶2 n-6先升高后下降,EPA、DHA呈相反趋势(P<0.05),C_(18)∶3 n-3先升高后下降再升高(P<0.05)。研究表明,随着孵化时间的延长,摄食前匙吻鲟仔鱼全长和体重均呈线性增长,摄食后均呈指数增长,2个阶段匙吻鲟仔稚鱼全长和体重均呈指数增长,体重与全长呈幂函数关系;前仔鱼期,匙吻鲟仔鱼对体内不同脂肪酸利用顺序为MUFA>n-6 PUFA>n-3 PUFA和SFA;摄食后,生物饵料脂肪酸组成对匙吻鲟仔稚鱼脂肪酸组成的影响日益显著。

During early development, fish go through a series of physiological and behavioral changes in response to their environment. This is the most vulnerable period for fish survival and is the critical stage for tissue and organ development. To better understand the growth regulation and energy metabolism of paddlefish （Polyodon spathula） larvae and juveniles before and after feeding, the growth characteristics and the fatty acid composition of paddlefish larvae and juveniles were characterized on day 3, 5, 7, 13, 19, 25 after hatching. The results provide a reference for continued research on the fatty acid nutritional needs and formulation of diets for paddlefish larvae and juven- iles. The test fish were reared in an indoor cement pool at 19 -23~C, DO 5.5 -8.0 mg/L, pH 7.2 -8.5 and NH4＋ GO. 2 mg/L and began to feed on zooplankton consifting of Cladocera and Cyclops on day 6 after hatching. Thirty paddlefish were sampled on days 3, 5 and 7, and 10 paddlefish were sampled on days 13, 19 and 25. The total length, weight and fatty acid composition for all sampled fish were measured. Based on the data collected, growth rates were expressed as a function of time. Total length （cm） , prior to feeding diet, was L1 = 0. 1288t1 ＋ 0.7134 （ where t is growth time, 3 ≤t1 ≤ 7, R2 = 0. 9993 ） and, after feeding diet, L2 = 0.9133 e0.0785t2 （7 〈 t2 ≤ 25, R2 = 0. 9913） , and, over the entire experiment, L = 0. 8948e0.0796t （3 ≤t ≤ 25, R2 = 0. 9950）. The growth rates with respect to weight （g） were expressed as W1 =0. 0035tl -0.0032, before feeding （3≤t1≤7, R2 =0. 9932）, W2 = O. 0061 e0.1893,2, after feeding （7 〈 t2≤25, R2 = 0. 9948 ）, and W = 0. 0049e0.2004t （3≤ t≤ 25, R2 = 0. 9911 ） over the entire experiment. The relationship between weight and total length of the paddlefish larvae and juveniles was described by a power equation, W = 0. 007L2 513. During the pre-larvae stage, the saturated fatty acids （SFA） of paddlefish significantly increased with time, monounsaturated fatty acid （MUFA） decreased dramatically, and polyunsaturated fatty acids （PUFA） had no evident change. Among the PUFAs, linoleic acid （Cts： 2n-6）, a-lino- lenic acid （C18： 3 n-3） and n-6 PUFAs significantly decreased, EPA （C20：5 n-3）, DHA （C22： 6 n-3） and n-3 PUFA significantly increased. After feeding the diet, SFA for paddlefish larvae and juveniles initially increased and then decreased and MUFA showed a decrease-increase-decrease pattern. PUFAs presented an increase-decrease-in- crease pattern; CIs： 2n-6 increased and then decreased, EPA and DHA decreased and then increased and Cls： 3n-3 displayed an increase-decrease-increase pattern. In conclusion, the total length and weight of paddlefish larvae before feeding grew linearly, but growth was exponential after feeding. Generally, the total length and weight of paddlefish larvae and juveniles grew exponentially during early development and the relationship between weight and total length was best described by a power function. During the pre-larvae stage, the utilization of different fatty acids by paddlefish larvae was in the order of MUFA 〉 n-6 PUFA 〉 n-3 PUFA and SFA. After feeding the diet, the fatty acid composition of paddlefish larvae and juveniles was gradually and significantly affected by the fatty acid composition of the food organism.