Hermaphroditism can compensate for the sex ratio in the Astyanax scabripinnis species complex (Teleostei: Characidae): expanding the B chromosome study model

Differential Expression of Genes Related to Sexual Determination Can Modify the Reproductive Cycle of Astyanax scabripinnis (Characiformes: Characidae) in B Chromosome Carrier Individuals

“…Studies on the reproductive cycle in this species demonstrated that B− females have reproductive activity from July to December, while B+ females present a reproductive peak shorter and later, from December to February [35]. This regulatory effect could cause, in the case of females, later ovary development, since B+ females presented lower expression of foxl2a compared to a B− female, and extending male spermatogenesis due to the upregulatory effect on dmrt1 expression reported for B+ males of A. scabripinnis [31] (Figure 4).…”

“…This regulatory effect could cause, in the case of females, later ovary development, since B+ females presented lower expression of foxl2a compared to a B− female, and extending male spermatogenesis due to the upregulatory effect on dmrt1 expression reported for B+ males of A. scabripinnis [31] (Figure 4). Such an extended reproductive period may contribute to the maintenance of this chromosome and consist of an important adaptive advantage that maintains populations in small high-altitude streams, which are constantly susceptible to intense environmental variations and predation [35,50,51]. Regarding a disproportional sex ratio, our sampling did not demonstate such a difference, mainly because we chose not to do that.…”

“…Amplification was performed under the following conditions: 3 min at 94 °C, 35 cycles of 90 s at 90 °C, 90 s at 52 °C, and 90 s at 72 °C; followed by a post-cycling extension for 5 min at 72 °C. The obtaining of mitotic chromosomes and fluorescent in situ hybridization (FISH) with a whole chromosome painting B probe was carried out according to Vicari et al [37] and Cornelio et al [35]. Hybridization occurred under high-stringency conditions (2.5 ng/µL probe, 50% formamide, 2×·SSC, 10% dextran sulfate).…”

“…In fish, B chromosome carrier males of A. scabripinnis presented higher levels of dmrt1 expression during the maturation stage [31]. In addition, a correlation of the sex ratio with B chromosome carrier individuals of A. scabripinnis was made, where seasonal distortions increased the sex ratio in favor of females [32,33,34,35]. Moreover, B-carrying females demonstrated a delay in the reproductive peak, suggesting a possible adaptive role of the B chromosome in the reproductive cycle [35].…”

Changing sex for selfish gain: B chromosomes of Lake Malawi cichlid fish

“…In addition, Bs have been shown to influence population sex ratio 6,9,10,24 . It has been suggested that this effect may be the result of B chromosomes interfering with the normal mechanism of sex determination 21,23,25,26 .…”