Sex-Dependent Plasticity in Osmoregulation of Three-Spined Sticklebacks Exposed to Freshwater

Freshwater adaptation in euryhaline fish species, such as the three-spined stickleback, involves a complex physiological response to maintain osmotic homeostasis. Hormone prolactin plays a central role in this process, primarily targeting gills and intestine. Research from Lomonosov Moscow State University has shed light on the sex-dependent differences in osmoregulatory function in sticklebacks.

Key Takeaways:

• The study found that female three-spined sticklebacks exhibited increased intestinal expression of ion transporter genes, such as NKCC1a and NCC, and decreased expression of the gene encoding a3a subunits of Na/K-ATPase, during freshwater adaptation.
• In contrast, only males showed an increase in the gene expression in the intestine, and both sexes exhibited a significant decrease in gene expression in the gills.
• The research supports the hypothesis of sex-dependent plasticity in osmoregulatory function in sticklebacks, with females exhibiting a more pronounced response to freshwater adaptation.
• The study concluded that this pattern aligns with the previously reported stronger activation of the prolactin axis in females during freshwater adaptation conditions.
• The research involved the measurement of expression levels of specific genes in the gills and intestinal tissues of male and female three-spined sticklebacks under acute and chronic freshwater adaptation conditions.

The study's findings have significant implications for understanding the mechanisms of osmoregulation in euryhaline fish species and the sex-dependent differences in this process.

Statistics:

• The study involved the measurement of expression levels of 6 specific genes in the gills and intestinal tissues of male and female three-spined sticklebacks.
• The research found significant increases in the expression of NKCC1a and NCC genes in the intestines of female sticklebacks during freshwater adaptation.
• A significant decrease in gene expression in the gills was observed in both male and female sticklebacks during freshwater adaptation.

Sources:

• Expression of Ion Transporter Genes in Gills and Intestine of Male and Female Gasterosteus aculeatus L. Three-Spined Sticklebacks during Freshwater Adaptation. Biochemistry-moscow, 2025;90(9):1227-1239.
• NewsRx. Research Results from Lomonosov Moscow State University Update Knowledge of Pituitary Gonadotropins (Expression of Ion Transporter Genes in Gills and Intestine of Male and Female Gasterosteus aculeatus L. Three-Spined Sticklebacks during ...). Life Science Weekly. October 21, 2025; p 5125.