Transmission of ocular media in labrid fishes

Wrasses (Labridae) are the second largest family of fishes on the: Great Ba rrier Reef (after the Gobiidae) and, in terms of morphology and lifestyle, one of the most diverse. They occupy all zones of the reef from the very sh adow reef flats to deep slopes, feeding on a variety of fauna. Many wrasses also have elaborately patterned bodies and reflect a range of colours from ultraviolet (UV) to far red. As a first step to investigating the visual s ystem of these fishes we measured the transmission properties of the ocular media of 36 species from the Great Barrier Reef, Australia, and Hawaii, Ca lifornia and the Florida Keys, USA. Transmission measurements were made of whole eyes with a window cut into the back, and also of isolated lenses and corneas. Based on the transmission properties of the corneas the species c ould be split into two distinct groups within which the exact wavelength of the cut-off was variable. One group had visibly yellow corneas, while the corneas of the other group appeared clear to human observers. Five species had ocular media that transmitted wavelengths below 400 nm, making a percep tion of UV wavelengths for those species possible. Possible functional role s for the different filler types are discussed.