Visual fields of four batoid fishes: a comparative study

Area of Science:

• Comparative anatomy
• Sensory ecology
• Ichthyology

Background:

• Visual fields in elasmobranch fishes are poorly understood.
• Batoids (skates, rays) represent a diverse monophyletic group within Elasmobranchii.

Purpose of the Study:

• To quantify and compare the visual field characteristics of four batoid species.
• To test the hypothesis that visual field diversity reflects batoid morphology and ecology.

Main Methods:

• Quantification of monocular, binocular, and cyclopean horizontal and vertical visual fields.
• Comparative analysis across four batoid species representing a basal skate to derived rays.

Main Results:

• Significant differences in horizontal and vertical visual fields among species.
• All species exhibited anterior and dorsal binocular overlaps.
• Urobatis jamaicensis showed a 360° horizontal panoramic field; Rhinoptera bonasus had a 360° vertical panoramic field.
• Dasyatis sabina and R. bonasus had large anterior binocular overlaps but posterior blind spots.
• R. eglanteria and U. jamaicensis had smaller binocular overlaps but expansive peripheral monocular vision.
• The basal Raja eglanteria had the most reduced visual field compared to derived rays.

Conclusions:

• Batoid visual field characteristics are diverse and linked to their ecological niches and morphology.
• This study provides the first comparative assessment of visual fields in basal vertebrates.