Adaptations for amphibious vision in sea otters (Enhydra lutris): structural and functional observations.
J Comp Physiol A Neuroethol Sens Neural Behav Physiol
; 206(5): 767-782, 2020 09.
Article
in En
| MEDLINE
| ID: mdl-32666146
ABSTRACT
Sea otters (Enhydra lutris) are amphibious mammals that maintain equal in-air and underwater visual acuity. However, their lens-based underwater accommodative mechanism presumably requires a small pupil that may limit sensitivity across light levels. In this study, we consider adaptations for amphibious living by assessing the tapetum lucidum, retina, and pupil dynamics in sea otters. The sea otter tapetum lucidum resembles that of terrestrial carnivores in thickness and fundic coverage. A heavily rod-dominated retina appears qualitatively similar to the ferret and domestic cat, and a thick outer nuclear layer relative to a thinner inner nuclear layer is consistent with nocturnal vertebrates and other amphibious carnivores. Pupil size range in two living sea otters is smaller relative to other amphibious marine carnivores (pinnipeds) when accounting for test conditions. The pupillary light response seems slower than other aquatic and terrestrial species tested in comparable brightness, although direct comparisons require further assessment. Our results suggest that sea otters have retained features for low-light vision but rapid adjustments and acute underwater vision may be constrained across varying light levels by a combination of pupil shape, absolute eye size, and the presumed coupling between anterior lens curvature and pupil size during accommodation.
Key words
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Otters
/
Vision, Ocular
/
Adaptation, Physiological
Limits:
Animals
Language:
En
Journal:
J Comp Physiol A Neuroethol Sens Neural Behav Physiol
Journal subject:
CIENCIAS DO COMPORTAMENTO
/
NEUROLOGIA
Year:
2020
Document type:
Article
Affiliation country:
United States