2025-10-22 マサチューセッツ大学アマースト校
When the pituitary glands of salmon are themselves exposed to daylight, they light up with TSH (red and green). Credit: Stephen McCormick.
<関連情報>
- https://www.umass.edu/news/article/salmon-use-pituitary-glands-see-when-its-time-migrate
- https://royalsocietypublishing.org/doi/10.1098/rspb.2025.1611
魚類の下垂体は日長に直接反応し季節性を引き起こす The fish pituitary directly responds to daylength and drives seasonality
Stephen D. McCormick,Daniel J. Hall,Marty Kwok Shing Wong,Takehiro Tsukada and Björn Thrandur Björnsson
Proceedings of the Royal Society B Published:08 October 2025
DOI:https://doi.org/10.1098/rspb.2025.1611
Abstract
Seasonal timing is important for many critical life history events of organisms, and annual changes in daylength provide a reliable seasonal cue. In birds and mammals, photoperiod-driven seasonality is caused by changes in pituitary thyroid stimulating hormone (TSH), brain deiodinase (DIO) and triiodothyronine (T3), but it is unclear if a similar mechanism exists in fish. We used anadromous Atlantic salmon that migrate downstream and enter the ocean in spring to examine photoperiod signaling in fish. Manipulations of diurnal and circannual photoperiod cycles indicate that pituitary tshβb and brain dio2b transcription are long day signals that precede endocrine and physiological changes necessary for seawater entry. Exposure to long days caused increased dio2b transcription and T3 levels throughout the brain, and intracerebral T3 treatment resulted in elevated levels of plasma GH that drives migration physiology. Significant ambient light levels reach the pituitary, and transcription of non-visual opsins were found in the pituitary. The isolated (in vitro) pituitary directly responds to increased daylength with elevated tshβb transcription, the first time this has been shown in any animal. The results indicate that photoperiod-driven seasonality in fish is driven by direct light stimulation of the pituitary, expanding the known mechanisms of photoperiod responses in vertebrates.
