博士 / 國立臺灣海洋大學 / 環境生物與漁業科學學系 / 92 / ABSTRACT
The resident and migratory types of grey mullets Mugil cephalus have been distinguished by seasonal capture in the coast of Taiwan. However, adults and juveniles can not be separated morphologically into resident and migratory populations. Allozyme analysis was applied to estimate genetic variation between two types of grey mullets and to test whether they belong to different populations. After starch gel electrophoresis, glucose-6-phosphate isomerase (GPI) exhibited allelic polymorphism. The resident type contained GPI-A*135 and GPI-B, and the migratory type contained GPI-A*100 and GPI-B. In addition, GPI activity of the resident and migratory types expressed different kinetic patterns, and GPI activities of locus A showed two distinct profiles between the two types of mullets. The results broadly revealed that GPI-A allelic frequency was not regulated by environmental changes in resident juveniles even after 6 months thermal acclimation. These findings suggest that the GPI-A allelic difference can be used for population discrimination.
The cirumtropically distributed grey mullet (Mugil cephalus) which occurs in waters surrounding Taiwan on the western Pacific fringe is divided into at least two stocks (migratory and residential), but questions regarding the level of genetic divergence and gene flow between them remain to be answered. To cast more light on this, allozyme variations at 21 presumptive gene loci of 1217 adult grey mullet from 15 localities and 4 gene loci from 1522 juveniles from 3 localities were analyzed. The observed heterozygosity (Ho) widely ranged from 0.003 (Kaohsiung) to 0.031 (Nagasaki), and the higher overall mean Fst of 0.303 indicates a very great genetic differentiation among the samples investigated. The results of the investigation for all localities indicated that the frequency of the GPI-A genotype significantly changed with latitudes, e.g., an increase in GPI-A* 135/135 homozygote frequencies and GPI-A* 100/100 frequencies were well correlated with latitudinal cline. The GPI-A genotype in all migratory populations was almost exclusively the GPI-A* 100/100 homozygote. During the life history of the grey mullet, the frequency of the GPI-A* 100/135 heterozygote significantly decreases with age. These data indicate that each GPI-A genotype represents the highest fitness in some portion of the environment.
| Identifer | oai:union.ndltd.org:TW/092NTOU5451002 |
| Date | January 2004 |
| Creators | Chao-Sheng Huang, 黃朝盛 |
| Contributors | , 陳哲聰, 李信徹 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 162 |
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