Colour vision in billfish

• Published in: Philosophical transactions of the Royal Society of London. Series B. Biological sciences Vol. 355; no. 1401; pp. 1253 - 1256
• Main Authors: Fritsches, Kerstin A., Partridge, Julian C., Pettigrew, John D., Marshall, N. Justin
• Format: Journal Article
• Language: English
• Published: England The Royal Society 29-09-2000
• Subjects: Anatomy; Animals; Color Perception - physiology; Color vision; Colors; Colour Vision; Colour Vision. I. Signals and the Light Environment; Electrophysiology; Fish; Microspectrophotometry; Mosaic; Perciformes - physiology; Photoreceptor Cells, Vertebrate - physiology; Retina; Retinal Cone Photoreceptor Cells - physiology; Retinal Cone Photoreceptor Cells - ultrastructure; Retinal pigments; Sensory Deprivation - physiology; Spectral reflectance; Spectral sensitivity; Teleost; Ultraviolet; Ultraviolet Rays; Wavelengths
• ISSN: 0962-8436; 1471-2970
• DOI: 10.1098/rstb.2000.0678

Members of the billfish family are highly visual predatory teleosts inhabiting the open ocean. Little is known about their visual abilities in detail, but past studies have indicated that these fishes were likely to be monochromats. This study, however, presents evidence of two anatomically distinct cone types in billfish. The cells are arranged in a regular mosaic pattern of single and twin cones as in many fishes, and this arrangement suggests that the different cone types also show different spectral sensitivity, which is the basis for colour vision. First measurements using microspectrophotometry (MSP) revealed a peak absorption of the rod pigment at 484 nm, indicating that MSP, despite technical difficulties, will be a decisive tool in proving colour vision in these offshore fishes. When hunting, billfish such as the sailfish flash bright blue bars on their sides. This colour reflects largely in ultraviolet (UV) light at 350 nm as revealed by spectrophotometric measurements. Billfish lenses block light of wavelengths below 400 nm, presumably rendering the animal blind to the UV component of its own body colour. Interestingly, at least two prey species of billfish have lenses transmitting light in the UV waveband and are therefore likely to perceive a large fraction of the UV peak found in the blue bar of the sailfish. The possible biological significance of this finding is discussed.