Chromosome evolution of family Belontidae Fishes in
family Belontidae are member of order Perciformes. Most
of fishes in order Perciformes have diploid chromosome
number (2n)=48 and all chromosomes exhibited as telocentric.
As such, all ancestor chromosomes could be
telocentric with 2n=48 [11]. For the family Belontidae,
there are only 16 of all 46 species that have the
cytogenetic information. They have been distributed only
in South East Asia, India, Pakistan and Korea. Of all the
fifteen species found in Thailand, seven have been
investigated for their chromosomal details. The species
in family Belontidae show a variable chromosome
number ranging from 2n (diploid) = 16 to 2n=48,
however most show 2n=46 and 2n=48 which could beassumed as the diploid ancestral number. According to the
report of Calton and Denton [1] that demonstrated the 2n=
16 of chocolate gourami (S. osphromonoide), it is believed
that decrease in chromosome number may have been
derived as a consequence to frequent centric fusion or
tandem fusion, on the pattern observed in common
barking deer (Muntiacus muntjak).
The cytogenetic study of genus Trichogaster and
Trichopsis in Thailand [4, 8, 14] show 2n=46 as all
telocentric chromosomes. This shows that all species in
these genera have high similarity suggesting that their
ancestors conserve primitive chromosomal characteristics.
For the genus Betta there are reports of variable diploid
chromosome number (2n)=34 and 42 and increasing
amount of bi-arm chromosome [8]. The chromosomal
evolution of this genus may have resulted from the centric
fusion and pericentric inversion that lead to the less
chromosome number and also the increasing of fundamental
number (NF).