Could the Immune System Be the Missing Link in Sole’s Reproductive Puzzle?

Faro, Portugal, 6 June 2025 | Study investigates how thyroid hormones regulate immune genes during sole metamorphosis and their potential link to reproductive dysfunctions in aquaculture

Larva lenguado senegalés (Solea senegalensis)

A study led by the Centre of Marine Sciences at the University of the Algarve, in collaboration with IFAPA El Toruño, has revealed that thyroid hormones play a central role in regulating immune-related genes during the metamorphosis of Senegalese sole (Solea senegalensis). Published in General and Comparative Endocrinology, the research offers valuable insight into the complex hormonal coordination underpinning early development-a factor that could help explain the species’ persistent reproductive issues in aquaculture settings.

Using transcriptomic analysis across six key stages of larval development, the researchers identified over 8,000 genes with differential expression. Among these were 133 candidate immune genes potentially regulated by thyroid hormone, 84 of which contained thyroid response elements in the promoter regions.

According to these researchers, “thyroid hormones modulates the expression of immune-related genes directly by regulating transcription through thyroid response elements or indirectly through interactions with other pathways.” This regulatory effect was particularly marked during intermediate and late metamorphic stages, coinciding with an upsurge in immune gene expression linked to functional maturation of the immune system.

The study pinpointed several biological processes enriched in thyroid hormone-regulated genes, including “leukocyte differentiation, T cell activation, cytokine production, regulation of innate immune response, and erythrocyte and leukocyte homeostasis,” as detailed in the article.

A noteworthy finding was a strong correlation between the expression of genes in the immune system and those within the hypothalamic-pituitary-thyroid axis. As the researchers explain: “a significant correlation was observed between the expression profiles of Hypothalamus–Pituitary–Thyroid axis and immune genes during larval development.”

While the primary focus of the study lies in immunological regulation, its implications may extend further. The authors propose that disruption in hormonal coordination during early stages could impact other biological systems, particularly reproduction-a longstanding challenge in Senegalese sole farming. Proper thyroid function during larval development, they suggest, could be key to ensuring healthy maturation and reproductive capacity in adulthood.

The identification of th-sensitive immune and endocrine genes not only enhances our understanding of larval physiology but also opens avenues for developing early-stage biomarkers, allowing hatcheries to monitor larval quality and better anticipate future reproductive performance.

Reference:

Sandra C. Silva, Teresa M. Correia, Manuel Manchado, Deborah M. Power. Metamorphosis-associated immune system maturation in Senegalese sole. General and Comparative Endocrinology. Volume 369, 2025, 114755, ISSN 0016-6480

https://doi.org/10.1016/j.ygcen.2025.114755