Aquaculture, 18 (1979) 325- 336 325 o Elsevier Scientific Publishing Company, Amsterdam - Printed in The Netherlands COMPARATIVE KARYOLOGICAL STUDIES ON CHINESE CARPS TERESA MARIAN and ZOLTAN KRASZNAI Fish Culture Research Institute, Genetics and Breeding Department, P. 0. Box 4 7, H- 5541 Szarvas (Hungary ) (Accepted 15 May 1979) ABSTRACT MPiln, T. and Krasznai, Z., 1979. Comparative karyological studies on Chinese carps. Aquaculture, 18: 325- 336. Comparative karyological studies on Chinese carps (Ctenophary ngodon idella. Aris- tichthys nobilis, Hypophthalmichthys molitrix) w ere carried out to determine the possibilities of hybridization. The diploid chromosome number, the morphological distrid bution of chromosomes, the arm ratio, the total and relative lengths of chromosomes, the total length of chromosome sets, and the number of arms were determined. Cross-breeding of grass carp and bighead was tested, and resulted in viable progeny. Karyological analyses of the F, hybrid generation were made. The hybrid proved to be triploid. INTRODUCTION Herbivorous fishes were first introduced to Hungary in 1963. Since then, all three species -the grass carp zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDC (Ctenopharyngodon idella), the bighead (Aristichthys nobilis), and the silver carp (Hypophthalmichthys molitrix) - have become very important and are raised at fish farms throughout the country. Their economic significance is constantly increasing. Their fast growth qualities make it necessary to investigate the genetic background of these fish, and the possibilities of cross-breeding. This paper gives the results of karyological investigations of the three Chinese carps, including a new hybrid of grass carp and bighead produced on the basis of the results of these investigations. MATERIAL AND METHODS Fish weighing 20-80 g were used for the karyological research. Doses of 0.01 ml/g body weight colchicine solution were injected intraperitoneally (M&i&r and Krasznai, 1978). After 18-20 h the kidney was prepared and processed. Distilled water was used for hypotonising. Fixation was conduc- ted for 30 min in a freshly prepared and cooled mixture of methanol and acetic acid in a ratio of 3:l. Preparations were made using the routine