Morphology of the eye and surrounding structures of calf and adult southern right whales (Eubalaena australis)

BUONO,M.; FERNÁNDEZ, M. ; HERRERA, Y.

Conferencia; Sixth Triennial Conference on Secondary Adaptation of Tetrapods to Life in Water; 2011

The last years have seen a growing interest in the anatomy and optics of the visual system of cetaceans (Mass and Suppin, 2007). However, much of this work has focused on odontocetes, and so far relatively little is known about the visual anatomy of baleen whales (Kröger and Katzir, 2008). Here, we report new observations on the anatomy of the eye of the southern right whale (Eubalaena australis), thus contributing to the further exploration of the visual capabilities of mysticetes. Eye samples were collected from 27 calves and 4 adult right whales, which had stranded near their nursery ground off Península Valdés, Argentina, over six years (2003; 2006 to 2010). In addition to providing anatomical descriptions of the eyeball and extraocular structures, we also collected quantitative data in the form of eyeball, corneal, scleral and lens measurements. Comparisons of calves and adults indicate different morphologies and growth patterns of the cornea, sclera and eyeball. The eyes of the calves differed from that of the adults in being more spherical and a lack of periorbital fat surrounding the posterior portion of the eyeball. We also found a correlation between body length and eyeball size, as previously reported for the closely related bowhead whale Balaena mysticetus (Zhu et al., 2001). By contrast, the dimensions of the cornea were only weakly correlated with body length. We found no correlation of the latter with the dorso-ventral height of the cornea and low correlation with the rostro-caudal corneal width.