Unique iris and pupil morphology in lamnid sharks

Documentation of the iris concentrating on color, pupillary shape, and orientation has been reported in a number of elasmobranch species, but has not been documented in lamnid sharks. This study examined the eyes of three lamnid sharks, white shark (Carcharodon carcharias), mako shark (Isurus oxyrinchus), and porbeagle shark (Lamna nasus) to characterize the iris color and pupil shape. All three species possess a brown color iris circling a horizontal slit pupil. A blue limbal ring of color circles the iris caused by the sclera and cartilage from the limbus which extends into the anterior chamber of the eye. The unique characteristics of the iris and pupil shape are described and implications of these findings on future research are discussed.