| To study the growth and development characters of offspring of the Chinese Mitten Crab (Eriocheir sinensis) produced by female parents with varied body weight, we raised the offspring in the crab cages placed in a pond and performed four handlings (Fig. 1, 2). Group A: offsprings produce by females weighed 175.7 ± 5.3 g; group B: offsprings from females weighed 150.4 ± 5.8 g; group C and D: offsprings from females weighed 125.6 ± 5.5 g and 100.2 ± 5.9 g. The paternity of all the offspring were weighed 300.2 ± 9.6 g. We farmed 500 offspring of E. sinensis in each cage which is shaded by Altemanthena philoxeroides. We randomly sampled 30 offspring from each cage when 80%﹣85% individuals of the crab exuviated their shells according to the shelling curcles. Totally, we took 11 samples from each cage. We weighed each individual by analytical balance scale and measured hell length and width, body height by electronic digital calipers after drying their external water using absorbent paper. The took the vertical distance from the depression of head central to the tail as the shell length and the widest part of the shell is used as the shell width, the vertical distance between the highest point of the back and abdominal as the body height. We udsed Excel and SPSS 22.0 software to analyze our data. After 158 days of cultivation, the weight of offspring increased from 6.0 ± 0.5 mg to 7 599.8 ± 954.78 mg for group A, 6 232.7 ± 638.68 mg for group B, and 6 112.4 ± 854.63 mg, 5 316.0 ± 745.25 mg for group C and D,expectively. The specific growth rate of offspring in group A was significantly higher than those in group D (P < 0.05). The weight of group A was significantly higher than B, C, D group after 6﹣11 times molting (P < 0.05); The weight of D group was significantly lower than those in group A, B, C at the 6th, 7th, 10th, 11th times of molting (P < 0.05) (Fig. 3, Table 2). The shell length of individuals in group A was significantly longer than those in group B, C, D group at the 7th, 8th, 10th, 11 th times of molting (P < 0.05); the shell length of individuals in group D was significantly short than those in group A, B, C after the 11th times of molting (P < 0.05) (Fig. 4, Table 2). Except the 3th times of molting, the shell width of offspring in group A was significantly wider than those in group B, C, D (P < 0.05); the shell width offspring in group D was significantly narrower than those in group A, B, C group after the 9th and 11th times of molting (P < 0.05) (Fig. 5, Table 2). Except the 3th and 6th times molting, the body height of individuals in group A was significantly higher than those in group B, C, D (P < 0.05); the body height of individual in group D was significantly lower than those in grougp A, B, and C after the 2th, 8th, 9th, 10th, 11th times of molting (P < 0.05) (Fig. 6, Table 2). The best composite indicator (weight, shell length, shell width, body height) of the juvenile crab was taken in the individuals in group A which was significantly better than those in group B, C, D (P < 0.05); The next best measurement was taken from in dividuals in group B and C. All the measurement taken from individuals in group D was worst. No any significant difference in all the measurement taken from individuals from group B and group C (P > 0.05), all the composite indicators from offspring in Group B and C were significantly better than the those from group D (Table 2). The highest survival rate was taken from group B which was 1.4%, 3.6%, 4.6% higher than those from group A, D and C respectively; this value from group A was 2.2% and 3.2% higher than that from group D and group C respectively. The survival rate from individuals in group D was 1.4% higher than that from group C (Table 3). Our study indicated that in the one year seed breed phase, the offspring produced by female parent with larger sizes had a superior growth traits than those produced by female parent with smaller sizes. |
