Evaluating seasonal changes of cone photoreceptor structure in the 13-lined ground squirrel

Cone photoreceptors of the 13-lined ground squirrel (13-LGS) undergo reversible structural changes during hibernation, including cone outer segment disc degeneration and inner segment mitochondria depletion. Here, we evaluated cone structure with adaptive optics scanning light ophthalmoscopy (AOSLO)...

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Bibliographic Details
Published in:Vision research (Oxford) 2019-05, Vol.158, p.90-99
Main Authors: Sajdak, Benjamin S., Salmon, Alexander E., Litts, Katie M., Wells, Clive, Allen, Kenneth P., Dubra, Alfredo, Merriman, Dana K., Carroll, Joseph
Format: Article
Language:English
Subjects:
Adaptive optics
Animals
Cone photoreceptors
Electron microscopy
Female
Ground squirrel
Hibernation
Male
Microscopy, Electron, Transmission
Ophthalmoscopy - methods
Photoperiod
Retinal Cone Photoreceptor Cells - cytology
Retinal Cone Photoreceptor Cells - ultrastructure
Sciuridae - anatomy & histology
Seasons
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Summary:Cone photoreceptors of the 13-lined ground squirrel (13-LGS) undergo reversible structural changes during hibernation, including cone outer segment disc degeneration and inner segment mitochondria depletion. Here, we evaluated cone structure with adaptive optics scanning light ophthalmoscopy (AOSLO) before, during, and after hibernation. Also, intra-animal comparisons of cone structure were made at distinct physiological states (pre-hibernation, torpor, interbout euthermia, and post-hibernation) with AOSLO and transmission electron microscopy. Our results indicate that the 13-LGS cone mosaic is only transiently affected by structural remodeling during hibernation. Outer segment remodeling starts during torpid states during a period of fall transition in room temperature, with more severe structural changes during bouts of torpor in cold temperature. Cones return to euthermic-like structure during brief periods of interbout euthermia and recover normal waveguiding properties as soon as 24 h post-hibernation. Cone structure is visible with split-detector AOSLO throughout hibernation, providing evidence that intact outer segments are not necessary to visualize cones with this technique. Despite the changes to cone structure during hibernation, cone density and packing remained unchanged throughout the seasonal cycle. Pairing non-invasive imaging with ultrastructural assessment may provide insight to the biological origins of cone photoreceptor signals observed with AOSLO.
ISSN:0042-6989
1878-5646
1878-5646
DOI:10.1016/j.visres.2019.02.009