Aquaculture, 38 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA (1984) 335-345 Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands 335 AN INVESTIGATION OF ENZYME AND OTHER PROTEIN POLYMORPHISMS IN JAPANESE STOCKS OF THE TILAPIAS zyxwvutsrqponmlkjih ~REOCHR~M~S~i~UT~CUS AND TILAPIA zyxwvutsrqponmlkjihgfedcbaZYXWVUTS ZILLJI Z.U. BASIAO’ and N. TANIGUCHI’ 1 Aquaculture Department, Southeast Asian Fisheries Development Center, Binangonan Research Station, Rinangon~n, Rizal (The Ph~lipp~nes~ z Koehi Universj~, Faculty of A~icul~re, 3200 Monobe, Nankoku 783 ~Japan~ Contribution No. 138 of the Aquaculture Department, Southeast Asian Fisheries Development Center. Reprint requests should be addressed to Ms. Z.U. Basiao. (Accepted 26 October 1983) ABSTRACT Basiao, Z,U. and T~~~h~, N., 1984. An investigation of enzyme and other protein poly morphisms in Japanese stocks of the tilapias Oreochromis niloticus and Tilapia zitlii. Aquaculture, 38: 335-345. Samples of Oreochromis niloticus and Tilapia zillii were collected from the hatcheries of Osaka Prefecture Fisheries Experimental Station and Shiga Prefecture Fisheries Experi- mental Station, Japan, respectively. The samples were used for screening polymorphisms in 13 enzymes, skeletal muscle proteins and hemoglobins by horizontal starch gel electro- phoresis. Among 35 loci examined, 12 loci for the 10 enzymes, sarcoplaamic protein and hemoglobins were polymorphic in 0. niloticue and 2 loci for 2 enzymes were polymor- phic in T. zillii. The observed numbers of phenotypes for respective loci agreed well with Hardy-Weinberg expectations. The genetic basis for each polymorph~m is discussed. This investigation provides basic information on the status of these tilapias in Japan. INTRODUCTION The tilapias are becoming an important species group for fish culture and applied research in many tropical and sub-tropical countries. They have been transferred intentionally or accidentally to various places outside their orig- inal areas of distribution and, since they interbred, have formed hybrids. This can make the morphometric identification of available stock difficult. Identification may be easier if electrophoresis is used along with traditional morphometric measurements. Electrophoresis of different proteins or enzymes has been widely applied in biological research. Many workers have shown that proteins and enzymes are useful genetic markers for fish in culture and breeding studies. Wohlfarth and Hulata (1983) have summarized recent work on applied genetics in 0044-8486l84/$03.00 0 1984 Elsevier Science Publishers B.V.