ScienceAsia 5 (1979): 017-026 |doi: 10.2306/scienceasia1513-1874.1979.05.017

CYTOGENETIC STUDIES OF SIAMESE FIGHTING FISH (BETTA SPLENDENS REGAN)

SUPAPORN RATANATHAM^a and SUDSANONG PATINAWIN^b

Summary: Domesticated Siamese fighting fishes are characterized into short fin and long fin types. The short fin fishes are much more aggressive than the long fin type. The purpose of this study was to determine whether they belong to the same species based on karyotype and hybridization evidence.

          Metaphase karyotypes of the short and long fin types are similar. Diploid number and arm number are 42 and 56 respectively. Chromosomes are graded into 3 groups; the first sixteen pairs are large size, the 11th and 18th pairs are medium size. and the last three pairs are small size. The centromeric type consist of seven pairs of submetacentric and fourteen pairs of acrocenrric. In this investigation, heteromorphic sex chromosome was not detected. However, polymorphism of chromosome Number 3 was observed in both types of fish.

          Sixteen pairs of reciprocal crosses and twenty backcrosses were performed. The rates of hatching and surviral of F₁ offspring from the reciprocal crosses of the short fin and the long fin types show no statistically significant differences. Backcrosses of tell male and ten female F₁ offspring were completely fertile. Therefore. both types of Siamese fighting fish should be regarded as the same species, Betta splendens (Regan).

Download PDF

a Department of Biology, Faculty of Science, Mahidol University, Rama VI Rd., Bangkok, Thailand and
b Department of Biology, Faculty of Science, Chulalongkorn University, Phyathai Rd., Bangkok, Thailand

Received 20 December 1978