Orchestrating change: The thyroid hormones and GI-tract development in flatfish metamorphosis

Area of Science:

• Developmental Biology
• Endocrinology
• Fish Biology

Background:

• Flatfish metamorphosis involves significant morphological and physiological changes for adapting to benthic life.
• Thyroid hormones (THs) are critical regulators of vertebrate development, including flatfish metamorphosis.
• The gastrointestinal tract (GI-tract) undergoes substantial modifications to support a diet shift from pelagic to benthic feeding.

Purpose of the Study:

• To review the role of THs in GI-tract maturation during flatfish metamorphosis.
• To identify gene transcripts and biological processes associated with GI-tract development in Atlantic halibut.
• To highlight advances and challenges in understanding TH-driven stomach organogenesis.

Main Methods:

• Review of existing literature on flatfish metamorphosis and thyroid hormone action.
• Analysis of gene expression patterns and gene ontology during Atlantic halibut metamorphosis.
• Characterization of molecular, structural, and functional changes in the GI-tract.

Main Results:

• Thyroid hormones trigger stomach organogenesis in flatfish.
• Specific gene transcripts and biological processes linked to GI-tract maturation were identified in Atlantic halibut.
• Gene ontology analysis revealed core functions and potential TH-responsive genes in GI-tract metamorphosis.

Conclusions:

• THs are essential for the development of a functional GI-tract, particularly the stomach, during flatfish metamorphosis.
• Understanding the precise molecular mechanisms of TH action on GI-tract development remains an ongoing challenge.
• Further research is needed to fully elucidate the complex interplay of factors governing TH-driven metamorphosis in Atlantic halibut.