Effect on growth and reproduction of hormone immersed and masculinized fighting fish Betta splendens

Abstract

To produce all-male progenies in the fighting fish, Betta splendens, six groups of fry were subjected to discrete immersion treatment at different 17alpha-methyltestosterone (MT) doses (viz. 100, 200, 500, 700, 900, and 1,000 microg/l) for a constant duration (3 hr/day) and frequency (second, fifth, and eighth day after hatching). The treatment at 900 microg/l led to 98% masculinization and 71% survival at sexual maturity. Treated groups, which showed significant deviation from the 1:1 sex ratio, were classified into two different series: S1 and S2. The groups that showed nearly cent-percent masculinization were classified as S1, and the other groups were classified as S2. The S1 males showed remarkably slower growth and attained 3.5 cm total length compared to 6.0 cm attained by a normal male. The S2 males attained 5.4 cm total length. Apart from these morphological defects, both S1 and S2 males suffered functional (decreased sperm count and sperm motility) and behavioral defects (incomplete embracing during mating) in their reproductive ability, leading to approximately 50% and 30% reduction in fecundity per mating, respectively. The cumulative fecundity loss suffered by the S1 male during its active reproductive phase is discussed. When normal and sex-reversed males were presented, a female preferred the former. Progeny testing of the sex-reversed males showed the occurrence of 12.75% males, indicating the possible role of autosomal genes in the sex determination mechanism of this species. Discrete immersion treatment at optimal/super-optimal doses ensured not only a higher percentage of masculinization, but also a higher frequency of homogametic males (XX).

Identification of neomales in South American catfish Rhamdia quelen on the basis of the sex ratio in the progeny

“…This outcome does not occur in some species owing to the influence of other genetic and environmental factors (particularly temperature) on sex determination, in addition to the influence of sex chromosomes (Devlin and Nagahama, 2002;Kirankumar and Pandian, 2002;Desprez et al, 2006). Progeny tests with XX neomales of Betta splendens produced 13% males in the progeny, indicating the possible participation of autosomal genes in sex determination (Kirankumar and Pandian, 2002).…”

“…This outcome does not occur in some species owing to the influence of other genetic and environmental factors (particularly temperature) on sex determination, in addition to the influence of sex chromosomes (Devlin and Nagahama, 2002;Kirankumar and Pandian, 2002;Desprez et al, 2006). Progeny tests with XX neomales of Betta splendens produced 13% males in the progeny, indicating the possible participation of autosomal genes in sex determination (Kirankumar and Pandian, 2002). In Perca fluviatilis, crosses between normal females and neomales result in progeny comprising 95-100 % females, whereas normal males of this species generate an unbalanced sex ratio that could be in favor of either sex (Rougeot et al, 2002).…”

“…However, for some species, sex chromosomes and autosomal genes determine the sex, and the latter are influenced by genetic and environmental factors. This sex-determining mechanism would limit the development of all-female progeny using neomales or superfemale breeders (Devlin and Nagahama, 2002;Kirankumar and Pandian, 2002;Desprez et al, 2006).…”

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“…Published results document attempts to enhance the number of males per litter or to make the females look more colourful [33][34][35] . In Thailand, breeders have used a variety of concoctions to enhance the male/female ratio, e.g., mangosteen (Garcinia mangostana) leaf extract.…”

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“…The main factors affecting the success of sexreversal are the selection of the appropriate steroid (androgen), the reliability and simplicity of the applied protocol (including doses, feed preparation, and treatment timing related to gonadal development), and the synchronization of offspring production 5, 9-11 . All-male production of Siamese fighting fish has been achieved by immersing the fry in 17a-methyltestosterone (MT) solution using concentrations of 100-1000 mg/l at 2, 5, and 8 days posthatch (dph) 12 . Similarly, norethindrone with doses of 250-1250 mg/l for 3 h on 2nd, 5th, and 8th dph has produced all males 13 .…”