Geographic variation of muscle adenylate kinase in the loach Misgurnus anguillicaudatus

Summary The electrophoretic pattern of the loach muscle adenylate kinase was composed of one or two major bands. Each major band was preceded by two minor bands. Three codominant alleles were postulated to segregate in loach. Each allele coded for one major band with different mobility. Adenylate kinase (AK. E.C. 2.7.4.3.) catalyses the reaction 2ADP ATP + AMP. and is known as a heat stable protein constituent of skeletal muscle. Electrophoretic variation of AK has been reported in the pika Ochotona r. rufescens (Vergnes et al. 1974). the teleostean fish Zoarces viviparus (Frydenberg & Si‐monsen, 1973), the mussel Mvtilus edulis (Ahmad et al. 1977). and the tunicate Ciona intestinalis (Schmidtke & Engel. 1980). In this note, individual variation of AK in muscle extracts of the fresh‐water fish Misgurnus anguillicaudatus is described. Loach were collected in ponds or purchased from fish shops (Table 1 & Fig. 1). Three populations (OS. AS and KN) were purchased from fish shops in Osaka. Akashi and Kanazawa cities, respectively. Their exact sampling locations were not known. For reference, the locations of these cities are indicated by an open circle in Fig. i. Fish were collected and stored frozen at – 20 o C at the sampling time given in Table 1. Muscle extracts were prepared and examined in the period February‐April 1981.The method for preparing muscle extract and‐the starch gel electrophoretic procedures were the same as those reported previously (Kimura, 1976). The amine‐citrate buffer system as described by Clayton & Tretiak (1972) was used. AK was stained by the method of Allendorf et al. (1977). After electrophoresis, an inhibition test was also performed by immersing the gel in 10 ‐3 M 5.5'‐dithiobis‐(2‐nitrobenzoate) solution for 30 minutes at room temperature. Under the electrophoretic condition used in the present study, all of the AK