Studies On Isozymes Of Glyptosternon Maculatum

Glyptosternon maculatum (Siluriformes: Sisoridae), is one of the Glyptosternoid catfish species. G. maculatum, inhabiting in the cold-waters of highland, only distributes in the middle-reach of Yaluzangbu River (the reach from Xietongmen to bomi) in Tibet, and in Brahmaputra River of India. There are some reports about G. maculatum mainly focus on its taxology, biogeography and the phylogeny of Glyptosternoid fishes. No reports on biochemical genetics of G. maculatum or other Glyptosternoid fishes were found.In present studies, 14 isozymes were investigated by polyacrylamid gel electrophoresis (PAGE). Muscle tissues of samples from 3 geographic groups, collected from Xietongmen reach, Lasha river and Niyang river (both the tributaries of Yaluzangbu River) in 2003, were used for PAGE analysis. The genetic identity (I) and genetic distance (D) were calculated by them to test the genetic differentiation among geographic groups located in different altitudes. Different tissues, including heart, liver, brain, eye, muscle, spleen and kidney of G. maculatum collected from Niyang river in 2005, were used for PAGE to analyze the tissue-specificity genetic variation appraised by the tissues with a high isozymic polymorphism. Some effective measures to protect the resource of G. maculatum population are suggested in the thesis, according to the condition of its habitat and genetic variation. So some referable knowledge and theoretical foundations generated during the studies can help the investigations and exploitations on natural resources of G. maculatum population as well as its protection.The main results are as follows:1. There was no sexual difference in isozymic expression.2. There was no significant biochemical genetic difference among geographic groups.3. There was no difference in isozymic expression between exo-celiac liver and celiac liver, which confirmed that the exo-celiac liver of G. maculatum has the same physiological function.4. Isozymic expression in G. maculatum has tissue-specificity. ADH isozymes was expressed in livers zymograms with the most bands and the strongest activity, while muscles with the least bands and weakest activity. AO isozymes only showed liver-type (Ao-A₄) with stronger activity and muscle-type (Ao-B₄). There were 5 bands with strong activity expressed in the liver EST zymograms, while only 1 band in brain and kidney, and no band was expressed in other tissues. GDH in the liver expressed dominantly, and in eye, with the weakest activity. Ldh-A₄ isozyme expressed dominantly in the muscle, while -B₄ isozyme dominated in liver, heart and spleen; Ldh-C₄ was found in the liver, spleen and kidney. There were supernatant (s) and mitochondrial (m) types found in MDH and MEP isozymes, both expressed dominantly in liver. No zymograms of GcDH and POD isozymes were pigmented in muscles. Only 1 band was examined in SDH zymograms in heart, eye and muscle, but 2 bands in other tissues. SOD was tested only one type of isozyme (m-SOD) in all tissues except the liver, in which expressed dominantly with 2 types (s-SOD and m-SOD).5. It was proved that the population of G. maculatum has a high isozymic polymorphism. Totally 14 polymorphic loci were found among 27 gene loci of the 10 tested isozymes. The whole percentage of polymorphic loci of G. maculatum is 0.5185. The P varies with the different tissues: muscle＞heart＞liver. The average heterozygosities (both Ho and He), ranging from 0.0201 to 0.0533 and from 0.0310 to 0.0485 (average 0.0370 and 0.0405), respectively, with the low ability of genetic variation, also vary with the different tissues: liver＞heart＞muscle.6. It was verified by chi-square test that the population of G. maculatum conforms to Hardy-Weinberg equilibrium.7. There are 6 polymorphic loci which were divergent from Hardy-Weinberg equilibrium. The genetic divergence index suggested that there was heterozygote excess in Adh-A (when expressed in liver) and Ldh-B (when in heart and liver) loci. And there was a serious phenomenon of heterozygote deficiency in Adh-B (when in heart and muscle), s-Mep-A (when in muscle), s-Mep-B (when in heart and muscle) and rn-Mep-C loci (when in liver). Further more, null alleles were found in the s-Mep-A and -B loci.