Purchase this article with an account.
T. Ren, M. L. Kisilak, C. J. Cookson, T. D. Singer, M. C. W. Campbell; In vivo Imaging of the Mosaic Pattern of Cones in Tilapia Oreochromis niloticus L. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4771.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
In vivo imaging of fish photoreceptors without dye injection would allow us to observe them in real time. We could then quantify photoreceptor type, size, spacing, and mosaic regularity. Oreochromis niloticus L. has been established as an important model for investigating stress and more recently to investigate refractive development. In addition, ongoing genome studies will allow for important complimentary molecular investigations.
Retinal twin cones were imaged in vivo in O.niloticus using Confocal Scanning Laser Ophthalmoscopy (CSLO). Fish used in this research were about 50g. 1~2.5ml 2-phenoxy ethanol per liter of water was used to stabilize eye movements and accommodation. Each fish was lightly restrained in a bath during imaging, and the water was changed every hour to refresh oxygen concentration. The imaging wavelength was 632.8nm. A -10D spherical trial lens was used in front of the fish eye to focus the photoreceptors. Differently polarized light was generated using a linear polarizer and a quarter wave plate and was scanned onto the fish retina with a 6° field of view (in air). Retinal images were recorded in real time. Eight frames were registered and averaged for each run in each fish.
A repeating twin cone mosaic pattern was observed. Single cones and rods were not resolved completely. The mosaic unit was a hexagon with six surrounding twin-cones and a center twin-cone. The orientations of the partitions of the twin-cones were perpendicular between neighboring columns. The diameter of O.niloticus twin-cones was about 10µm. The center-center spacing between neighboring twin-cones was about 20µm. The twin cone mosaic pattern was found to be highly ordered using Voronoi analysis of in-focus areas in the retinas of 3 fish. Twin-cones also lit up differently with differently polarized light.
O.niloticus twin-cone photoreceptors were successfully imaged in vivo for the first time, without dye, using a CSLO. Tilapia cone type, size, spacing, and mosaic pattern were observed, and were consistent with in vitro descriptions in the literature. O.niloticus twin-cones show interactions with polarized light, which are suggestive of polarization sensitivity.
This PDF is available to Subscribers Only