Morphological Characters Of Nibea Albiflora & Miichthys Miiuy And Genetic Research Of Nibea Albiflora Populations

Two most important commercial species, spotted maigre (Nibea albiflora) and Mi-iuy croaker (Miichthys miiuy) in part of the Yellow Sea & East China Sea, were analyzed by using some morphology means, such as biology observation,measurement and statistics analysis etc. As well as some genetics methods, such as isozyme analysis and mtDNA gene fragments sequencing comparison in order to exploit rationally the two Sciaenidae species and sustainably utilize them. Results of the research fill up the blank in the field of Sciaenidae species genetics. Meanwhile it is important to protect the genetics diversity of the marine fishes in our country.At the morphology aspect: Fistly, the biological characteristics of a Nibea albiflora population in the coastal waters of the Yellow Sea (Qingdao) and a Miichthys miiuy population in the East China Sea (Zhoushan) were analyzed in this paper. Morphological characters of the two species were described in detail. The frequency of body length and body weight in the two species were studied through conventional measurement and statistic analysis. The relationships between some biological parameters were analyzed. The relationship between body length (BL, cm) and body depth (BD, cm) of Nibea albiflora by separate regression curves as BD = 0.2847BL + 0.6121. The relationship between body length (BL, cm) and body weight (BW, g) of Nibea albiflora can be described with exponential equation: BW = 0.1682BL2.3052. The relationship between body length (BL, cm) and body depth (BD, cm) of Miichthys miiuy is expressed with a linear equation: BD = 0.2136BL + 0.6452. The exponential equation BW = 0.0568BL3.0295 was compatible for describing the relationship between body length (BL, cm) and body weight (BW, g) of Miichthys miiuy.Secondly, three natural Nibea albiflora populations (121 individuals) from the middle area of Yellow Sea(Qingdao), the north of East China Sea(Zhoushan) , the south of East China Sea(Xiamen) and a Miichthys miiuy population (24 individuals) were collected, 6 meristic characters and 7 measurement characters were analyzed by clustering, one-way ANOVA and principal components analysis. The result showed that highly significant difference in the morphological characters existed among the Miichthys miiuy population and the three Nibea albiflora populations else, such as Lateral scales,1st Dosal fin thorns,2nd Dosal fin rays,Lower gill rakers and Vertebrae (except the upper gill rakers),GH/AF,AB/AF,EF/AF,AC/AF,AI/AF,AD/AF and CD/AF .etc. Compared with the difference between the two species, the difference between the three populations of Nibea albiflora is much small. On the other hand, for the three Nibea albiflora populations, compared with the Qingdao population, it showed a trend of highly similarity between the populations of Zhoushan and Xiamen.At the genetics aspect: Firstly, horizontal starch gel electrophoresis was used to investigate the genetic structure of the three populations (Qingdao, Zhoushan and Xiamen) of Nibea albiflora. Ten loci were identified in the seven enzymes (G3PDH,IDHP,LDH,MDH,PGDH,PGM,SDH) analyzed. The proportions of polymorphic loci for populations were always 0.2. The average observed and expected heterozygosity ranged from 0.03 to 0.05 and from 0.03 to 0.04 respectively. The average number of efficient allele for each locus varied from 1.04 to 1.05. The genetic distance among populations were from 0.0004 to 0.0008, and the genetic similarity were from 0.9992 to 0.9996. The results showed that: There are not obvious genetic differentiation among the three populations of Nibea albiflora, respective genetic structures have not been established. It is said that different geographical populations haveobvious gene comunication between each other, so that the genetic difference between them is much tiny.Finally, With the method of PCR, the partial cytochrome b (Cyt b) gene was amplified to investigate three populations of Nibea albiflora and the differences were analyzed. By sequencing, the sequence of 420bp nucleotide was obtained. The average contents of T,C,A,G in the three populations of Nibea albiflora(Qingdao,Zhoushan and Xiamen) were 28.5%,31.0%,24.5% and 16.0%, respectively. The difference of the fifteen samples was much tiny. The contents of A+T of Cyt b gene fragments were always more than the contents of G+C within the three populations of Nibea albiflora. It was also found that the difference of the base sequences among fifteen samples was much tiny, belong to the difference level between species.