A Study On The Morphology And Genetics Of Lota Lata Linnaeus And Gadus Macrocephalus Tilexius

Burbot(Lota lota Linnaeus) and pacific cod(Gadus macrocephalus Tilesius) are important economic species in the family of cod. In the recent years, the resources of both species have been destroyed because of enviroment and over exploitation prolems. In the present study, the basic biological characteristics of burbot and pacific cod were studied in order to explore the basic biological features of both species and provide reference for its culture production.In addition, there are have been some debates on the classification of burbot and pacific cod, especially the subspecies taxonomic of burbot. But it is unwarranted to define any species or subspecies by only one taxonomic method. Steady and complicated morphology is an important method to study classification of fish. Horizontal starch gel electrophoresis has been applied to population genetics, species distinguish and heredity breeding. The sequence of cytochrome b have been extensively applied to classification and phylogenetic relationgships of fish. So we study the posture characteristics, the skeleton system, isozyme and the sequence of mtDNA cyt b gene, the results indicated that:1. Systematic measurement of the posture characteristics of burbot was compared between Eerqisi and Amur, significant variation was found in 24 posture characteristics and 6 of which were significant at subspecies level, the relationship formula between body length and weight of burbot and pacific cod is shown below:W=0.0168L2.7823(r=0.9800) w=0.5615L2.0062 (r=0.81173)2. Both burbot and pacific cod have well-developed nasals, frontal, opisthotic, and squamosal bones, but they have not orbitosphenoid, basisphenoid, pseudomesia bar, and supplemental maxilla. The outside of maxillary consists of premaxillary. There are teeth on the vomer. Supraoccipital and frontal are connected, and the right and left parietal are detached. Their caudal fins are equal tail. Most differences ofskeleton system between burbot and pacific cod are still on the shape, size or the developed degree of the crest.3. Of the 6 enzymes assayed routinely, 9 gene loci were found: PGM*, G3PDH-1*, G3PDH-2*, IDHP*, LDN*, MDH-1*, MDH-2*, SOD-1*, SOD-2*. There is a complete replacement of alleles at G3PDH-1* between burbot in Amur river and Eerqisi. Isozyme analysis indicated complete replacement of 9 gene loci between burbot and pacific cod.4. Partial segment of mitochondrial cytochrome b gene were sequenced for burbot from Amur river and Eerqisi river. Comparing data with those from genebank, the results indicated that burbots in Amur river were isolated from North America phylogroup and Eurasian-Beringian phylogroup. The genetic distance between burbot and pacific cod is 0.195, they diverged 9.745MY ago applying a divergence rate of 2%/ MY.In general, burbots in Amur river are a different phylogroup. We will continue to study whether the burbot in other places of Amur river and in Yalu river are similar to those studied in the present srudy. We hope that the results can make inference to the phylogenetic relationships of burbots worldwide.