Karyotype of the hybrid between Clarias macrocephalus gunther and Pangasius sutchi Fowler
1987
Prasit Sittikraiwong
Clarias macrocephalus had 26 pairs of chromosome which consisted of 9 pairs of metacentric chromosome, 10 pairs of submetacentric chromosome and 7 pairs of acrocentric chromosome, the fundamental chromosome number was 90. Pangasius sutchi had 30 pairs of chromosome which consisted of 9 pairs of metacentric chromosome, 11 pairs of submetacentric chromosome and 10 pairs of acrocentric chromosome, the fundamental chromosome number was 100. Clarias-like hybrid had chromosome number of 82 (allotri-ploid, 3n=82) by obtaining 2 genomes (2n=52) from Clarias and one genome (n=30) from Pangasius. The chromosome set consisted of 27 metacentric, 31 submetacentric and 24 acrocentric chromosomes, the fundamental number is 140. Chromosome arrangement was found as follows: 17 sets of trivalent, 9 pairs of bivalent from Clarias and 13 chromosomes from Pangasius were univalent. The Pangasius-like hybrid had chromosome number of 56 (amphidiploid, 2n=56) by obtaining one genome (n=26) from Clarias and one genome (n=30) from Pangasius. The chromosome set consisted of 18 metacentric, 21 submetacentric and 17 acrocentric chromosomes, the fundamental number was 95. The chromosomes that could be arranged in bivalent were 17 pairs and 22 chromosomes were univalent. The "actual Clarias" hybrids were supposed to arise from gynogenesis.
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