• The Korean Journal of Zoology
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• v.32 no.3
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• pp.232-241
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• 1989

Two cytosol malate dehydrogenase allelomorphs are found in the Dark Chub, Zacco temmincki, a freshwater fish inhabiting Korean waters. Mdh-1MM(hereafter referred to as A-type) is distributed along the south and southeastern parts of Korea, whereas the B-type(Mdh-1MS) is found everywhere except the southeast. Several syrnpatric populations can be found in the southern areas with no hybridization between them. The pattern of geographic distribution would indicate that A-type is superior adaptation to colder water temperature; this is collaborated by evidence collected from a sympatric length of the Tongchon stream, Namhae. The relative warmth of the water along this portion of the stream's length was determined its altitude and the time of year. Frequency of B-types found was directly proportional to the relative warmth of the water and inversely proportional to the nurnber of A-types found in the sarne station. Current data tends to suggest that the B-type of Zacco temrnincki first differentiated from Zacco platypus approximately one million years ago (Yang et al., 1984) while A-type subsequently branched from B-type 300,000 years later(Yang and Mm, 1987) through a progressive adaptation toward colder temperature.