Investigation into the pH of the Ocular Secretions of the Bottlenose Dolphin (Tursiops aduncus) with Corneal Disease
Corneal diseases are a common problem in captive populations of the bottlenose dolphin (Tursiops spp.) around the world. The pathogenesis of this disease is most likely multifactorial in origin and represents a significant management issue for this species. The tear film produced by terrestrial mammals plays an important role in the maintenance of ocular health; however, the role of these secretions in marine mammals is unclear.1,2 The pH of mammalian tear film has been shown to vary with some states of corneal pathology; however, this pattern has not been investigated in cetaceans.2-4 To investigate this process, the tear film pH from five Tursiops aduncus of mixed ages and sexes were measured daily over a four-month period. During this period, the animals were housed separately in pools that will be referred to as Dolphin Pool 1 (DP1) and Dolphin Pool 2 (DP2). An objective criterion was created to classify the degree of corneal disease. Scores ranged from zero to six, with zero representing a healthy eye and a grading of five used for severe disease. The score six was used for an eye following perforation of the cornea. Additional parameters including UV exposure, chlorine levels, exhibit water pH, and the presence or absence of oral and topical medications were also recorded.
There was a significant relationship between the disease condition of the cornea and the pH of the tear film (p = 0.0000); however, this relationship was complex and nonlinear. The salinity of DP1 accounted for a significant amount of the variance in eye pH (p = 0.0002), demonstrating a linear relationship whereby increasing salinity in that pool was associated with increased pH of the tear film. The temperature measured in DP2 also accounted for variance in tear film pH (p = 0.0004); however, this was not linear. DP2 was significantly colder than pool DP1, and the lack of a linear relationship between pool temperature and tear film pH suggests that the colder water in pool DP2 was associated with greater fluctuation of eye pH rather than a higher or lower pH per se.
The authors wish to thank the trainers at Dolphin Marine Magic for the time spent training animals and collecting samples.
* Presenting author
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