DOI: 10.5061/dryad.8gtht7721
title: Data from: The fish pituitary directly responds to daylength and drives seasonality:

description: 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.
description: # Data from: The fish pituitary directly responds to daylength and drives
 seasonality Dataset DOI:
 [10.5061/dryad.8gtht7721](10.5061/dryad.5x69p8dds) ### Files and variables
 #### File: Proc_Roy_Soc_London_B_all_data_final_d.xlsx **Description:**
 Data from: The fish pituitary directly responds to daylength and drives
 seasonality
 [https://doi.org/10.5061/dryad.8gtht7721](https://doi.org/10.5061/dryad.5x69p8dds) ## Description of the data and file structure Data are from photoperiod and experimental manipulations of juvenile Atlantic salmon. Each worksheet represents an experiment that is presented in a figure of the manuscript. Each row is an individual salmon. Each column is either a group (e.g. treatment, date) designation, or a parameter measured for that individual ### Worksheet descriptions: Fig 1c-f Response of juvenile Atlantic salmon to natural photoperiod (LDN) and continuous short days (SD; LD8:16). Fig 2a Time course of pituitary tshβb mRNA levels in fish under short days (SD, LD8:16) or after exposure to long days (LD, LD16:8) for 0,1,2,3, 6 and 10 days. Fig 2c-e Response of juvenile Atlantic salmon to increased daylength for 20 days. Experimental treatments were LD8:16, LD10:14, LD12:12, LD14:10 and LD 16:10. Endpoints were pituitary tshβb mRNA (C), hypothalamic dio2b mRNA (D) and plasma GH (E). Fig 2f Response of pituitary tshβb mRNA levels in juvenile Atlantic salmon to pulse light exposures during the subjective night (2 pulse LD) and subjective day (2 pulse SD). Fig 4a Changes in dio2b mRNA in the telencephalon (tel), cerebellum (CB), hypothalamus (hypo), preoptic area (POA) and midbrain/optic tectum (MB/OT) after 20-day exposure to long days (LD, LD16:8). Fig 4b Changes in Hypo/POA, MB/OT and plasma T3 levels following exposure to SD and LD for 20 days. Fig 4c Effect of intracerebral slow release T3 implant for 20 days on plasma GH levels in juvenile Atlantic salmon held under SD conditions Fig 5a Proportion of light reaching the pituitary compared to illuminance levels measured at the surface of the head. Fig 5b Tissue distribution of opsin3 mRNA levels in juvenile Atlantic salmon under SD conditions Fig 5c Levels of non-visual opsins mRNA levels of opsin5, parapopsin (popn), teleost-multiple-tissue opsin (tmtops) and opsin3 in the pituitary under SD (LD8:16) and LD (LD16:8) conditions for 20 days. Fig 5d Pituitary tshβb mRNA levels in isolated pituitaries in culture (in vitro) after exposure to SD (LD8:16) or LD (LD16:8) after 48 and 120 hours. Fig 5e Effect of in vitro temperature (3 or 12 C) and daylength (SD or LD) on pituitary tshβb mRNA levels. Pituitaries were removed from fish that had been under SD conditions at either 3 or 12 C and maintained under these temperatures through 4 days of culture. Fig 5f Effect of light levels and color composition of light on pituitary tshβb mRNA levels *in vitro*.  Fig 5g Effect of light levels and color composition of light on pituitary *tshβb* levels *in vivo*.  ### Variables * GH: Plasma growth hormone, ng/ml * NKA: gill NKA activity, umol ADP/mg protein/hour * tshbb: pituitary tshβb mRNA levels, relative units * dio2b: brain dio2b mRNA levels, relative units * hypo dio2b: hypothalamic dio2b mRNA levels, relative units * HB dio2b: hindbrain dio2b mRNA levels, relative units * MB/OT dio2b: midbrain/optic tectum dio2b mRNA levels, relative units * POA dio2b: preoptic area dio2b mRNA levels, relative units * hypo/POA T3: hypothalamus/preoptic area triiodothyronine content, nanogram/gram * MB/OT T3: Midbrain/Optic Tectum triiodothyronine content, nanogram/gram * plasma T3: Plasma triiodothyronine, nanogram/ml * % transmission: illuminance of light reaching the pituitary as a percent of illuminance measured at the surface of the head * opsin3: opsin3 mRNA levels, relative units * OB: optic bulb * SV: saccus vasculosus * opsin5: opsin5 mRNA levels, relative units * popn: paraopsin mRNA levels, relative units * tmtops: teleost-multiple-tissue opsin mRNA levels, relative units Missing values appear as blank cells ## Access information Other publicly accessible locations of the data: * none Data was derived from the following sources: * experiments conducted by the authors