| The red swamp crayfish, Procambarus clarkii, native species in the south-central of United States and the northeastern part of Mexico, has been a dominant species after induced into China since 1929. The IMP contents of muscle in different populations of the red swamp crayfish were measured by HCLP, the genetic diversity and genetic differentiation of different polulations of the red swamp crayfish were analyzed by microsatellites DNA molecular method and the relationships between morphological characters and genetic diversity of populations, between genetic differentiation and the IMP content in muscle were discussed. The main results were as follows:The IMP content in fresh muscle was lower and increased with the time. It reached the peak in the second day. The IMP contents did not differ significantly between the first day and the second day, so that it could be measured between 24 hours and 48 hours. The IMP contents of the red swamp crayfish in five natural populations and an artificial breeding population in muscle of the red swamp crayfish varied from 2.060 to 2.796mg/g, which was higher relatively. The IMP contents in muscle of the red swamp crayfish among Zhenjiang population, Shaobohu population and Gaobaohu population were not significantly different(P>0.05), but significantly lower than those in Weishanhu population and significantly higher than those in artificial breeding population(P<0.01). It indicated that the artificial breeding had an important effect on the flavor of the muscle in the red swamp crayfish.The differences of the body weight, bodylength, carapace length and muscle content of the red swamp crayfish among the six populations reached a remarkably significant level (P<0.01).The body weight of Weishanhu population were significantly different from those of the other five populations (P<0.05), and the body weight of other five population were not significantly different (P>0.05). The bodylength of Zhenjiang population were significantly different from those of the Shaobohu population, Gaobaohu population, Hongzehu population and Weishanhu population(P<0.05), but were not significantly different from that of Xinghua population. There was not significantly different among the bodylengthes of the Shaobohu, Gaobaohu, Hongzehu and Weishanhu populations. The carapace length of Weishanhu population were significantly more than those of Zhenjiang, Hongzehu and the artificial breeding population(P<0.05), and were not significantly different with others(P>0.05).The pincers length of Zhenjiang population were significantly lower than those of Weishanhu population and the artificial breeding population(P<0.05).The muscle content of Zhenjiang population were significantly lower than others(P<0.05).The number of alleles and effective alleles amplified from seven microsatellite locus varied from 3.00 to 10.00 and 1.93 to 3.56, respectively. The polymorphism information content (PIC) per locus ranged from 0.3919 to 0.6715 which showed that five loci were high-polymorphic while the other two were both medium-polymorphic. The mean values of observed heterozygosity (Ho), expected heterozygosity (He) and the polymorphism information content of the seven loci were 0.5615,0.6288 and 0.5460, respectively. The results above implied that the genetic diversity of the red swamp crayfish was high-leveled. The average fixation index (F) was above zero, indicating that heterozygosity was lost in the population. The distributing range of genetic differentiation index (Fst) was from 0.0206 to 0.0935 per locus and the mean value all loci was 0.0584. It implied that about 5.84% of the genetic variation existed in intrapopulation, while 94.16% of the variation existed in interpopulation. At the species level and the population level, there were significant deviations from Hardy-Weinberg equilibrium in Shaobohu and Hongzehu populations. The loci of PclG08 of zhenjiang population showed significantly imbalance, the one of PclG28 of Gaobaohu population showed significantly imbalance, the one of PclG04 and PclG08 of Weishanhu population showed significantly imbalance,and the one of PclG04 , PclG07, PclG08, PclG28, PclG29 and PclG17 of Xinghua artificial breeding population showed significantly imbalance.PIC and He values of Zhenjiang population were the highest among all populations, while PIC, Ho and He values of Weishanhu population were the lowest among all populations. However, PIC, Ho and He values did not differ significantly among all populations (p>0.05). Also, CV values of the morphological characters had no significant relationship with the genetic diversity (p>0.05). Mean pairwise genetic differentiation index (Fst) and gene flow (Nm) between Zhenjiang and Shaobohu populations were 0.0104 and 23.8328, respectively. While Mean pairwise Fst and Nm values between Weishanhu and Shaobohu populations were 0.0551 and 4.2879, respectively. It meant that the genetic differentiation between Weishanhu and Shaobohu populations had reached a medium level, but the genetic differentiation among other four populations was limited.The genetic distance (GD) and UPGMA cluster analysis were almost the same as from the genetic differentiation. Mean pairwise GD value between Weishanhu population and the other four populations was more than that among the other five populations. UPGMA cluster analysis showed Zhenjiang population and Shaobohu population clustered one firstly, and then clustered Gaobaohu population, Hongzehu population in turn. The Weishanhu population and Xinghua population were clustered as one.Pearson correlation analysis of morphological parameters and IMP contents showed that the relation between pincers length and IMP contents in pincers muscle or rump muscle was significant (r=0.857,P=0.029;r=0.853,P=0.031); the relation between other four morphological parameters and IMP contents was no significant(P> 0.05); Pearson correlation analysis revealed that the five characters and the coefficient of variation in IMP had no significant correlation (P> 0.05), and the population patterns of variation and IMP had no significant relationship.PclG07, PclG08 of red swamp crayfish had significant effect or a higher significant impact on body weight, body length, carapase length; PclG02 of red swamp crayfish had significant impact on the length of sequestration and muscle content; PclG28 of the swamp crayfish had significantly effect on the carapase length, respectivly. It seemed that these locus could be used for early selection of swamp crayfish corresponding characters and molecular marker-assisted selection.The relation of PclG08 loci and IMP content in carapase muscle was significant in the population of Zhenjiang; the relation of PclG28 and IMP content in carapase muscle was also significant in the population of Shaobohu; PclG17 loci and IMP content in rump muscle was remarkably significant in the population of Weishanhu; the relation of PclG02, PclG29 and IMP content in carapase muscle, PclG07, PclG08 and IMP content in rump muscle were significant or remarkably significant in the population of Xinghua. we could try to use these locus for early selection. |
