No evidence of accommodation in the eyes of the bottlenose dolphin, Tursiops truncatus.

Citation
Tl. Litwiler et Tw. Cronin, No evidence of accommodation in the eyes of the bottlenose dolphin, Tursiops truncatus., MAR MAMM SC, 17(3), 2001, pp. 508-525
Citations number
36
Categorie Soggetti
Animal Sciences
Journal title
MARINE MAMMAL SCIENCE
ISSN journal
08240469 → ACNP
Volume
17
Issue
3
Year of publication
2001
Pages
508 - 525
Database
ISI
SICI code
0824-0469(200107)17:3<508:NEOAIT>2.0.ZU;2-G
Abstract
Bottlenose dolphins (Tursiops truncatus) are aquatic mammals that must come to the surface to breathe. As a result, it might be expected that their ey es are adapted for both aerial and underwater vision. Earlier studies sugge st that dolphins are emmetropic (i.e., focused at infinity) in water, and i n some cases, emmetropic in air, although the mechanisms chat permit these animals to see well in both media are not well understood. Nor is it known whether they can accommodate to focus sharply on objects at different dista nces. We employed video photoretinoscopy to investigate the possibility of an active accommodative mechanism in the eyes of the bottlenose dolphin in water. Measurements of the refractive state in water indicated near emmetro pia for two individuals and slight myopia (nearsightedness) for the third i ndividual. No clear cases of accommodation were observed underwater in any of the subjects examined. Vision underwater may be used to supplement echol ocation. If so, such a role might not require an accommodative mechanism.