Chromosomes number and mitosis time of Siamese fighting fish (Betta splendens Regan, 1910)

Siamese fighting fish (Betta splendens) is originated from Southeast Asia and one of Indonesia’s most profitable exports commodity. However, scientific studies on Siamese fighting fish chromosomes remain limited. Chromosomal information is very useful for disclosing the diversity and genetic relationships of animals and provides clues to the most appropriate conservation measures for a species. Moreover, affordable chromosome visualization procedures are also a main concern for animal research. This research aims to determine the optimal chromosome preparation time, the best method for observing prometaphase, and the chromosomal characteristics of different types of betta fish based on their diploid numbers. The results showed that the optimal time for chromosome preparation is between 07:00 am and 12:00 pm and that the best method for observing chromosomes is the splash method from Kligerman and Bloom modified by soaking samples in colchicine for 11-12 h. The chromosome numbers of Giant, Plakat, Crown tail, and Halfmoon bettas are identical, i.e., 2n=42.