Visual pigment changes in rainbow trout in response to temperature

Area of Science:

• * Physiological optics
• * Aquatic animal physiology
• * Biochemistry of vision

Background:

• * Rainbow trout (Salmo gairdneri) possess different visual pigments, including rhodopsin and porphyropsin, which are sensitive to varying light conditions.
• * The proportion of these pigments can change in response to environmental factors, influencing visual adaptation.
• * Understanding these adaptations is crucial for comprehending fish behavior and survival in different aquatic environments.

Purpose of the Study:

• * To investigate the effect of water temperature on the proportion of porphyropsin in the retina of rainbow trout.
• * To determine if this temperature-dependent change in visual pigment follows a Q10 relationship.

Main Methods:

• * Rainbow trout were exposed to two different water temperatures: 6 degrees C and 16 degrees C.
• * Fish were subjected to different light conditions: constant darkness and a 12-hour light/12-hour dark cycle.
• * The proportion of porphyropsin in the retina was analyzed under these experimental conditions.

Main Results:

• * Lower water temperature (6 degrees C) significantly favored a higher proportion of porphyropsin in the retina compared to higher temperatures (16 degrees C).
• * This effect was observed consistently across both tested light conditions (constant darkness and 12L:12D).
• * The observed temperature-dependent shift in porphyropsin proportion did not exhibit a Q10 relationship.

Conclusions:

• * Water temperature is a critical environmental factor influencing the visual pigment composition in rainbow trout.
• * The retina of rainbow trout adapts to colder temperatures by increasing the concentration of porphyropsin, potentially enhancing vision in low-light or specific spectral conditions.
• * The non-Q10 response suggests a complex physiological mechanism underlying visual pigment regulation in response to temperature changes.