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- Title
Spectral sensitivities of the seahorses Hippocampus subelongatusand Hippocampus barbouriand the pipefish Stigmatopora argus.
- Authors
VIRGINIA MOSK; NICOLE THOMAS; NATHAN S. HART; JULIAN C. PARTRIDGE; LYN D. BEAZLEY; JULIA SHAND
- Abstract
The Syngnathidae are specialized diurnal feeders that are known to possess a retinal fovea and use independent eye movements to locate, track, and strike individual planktonic prey items. In this study, we have investigated the spectral sensitivities of three syngnathid species: a pipefish and two seahorses. We used spectrophotometry to measure the spectral transmission properties of ocular lenses and microspectrophotometry to measure the spectral absorption characteristics of visual pigments in the retinal photoreceptors. The pipefish, Stigmatopora argus, together with the seahorse Hippocampus subelongatus, is found in “green-water” temperate coastal seagrass habitats, whereas the second seahorse, H. barbouri, originates from a “blue-water” tropical coral reef habitat. All species were found to possess short wavelength absorbing pigment(s) in their lenses, with the 50% cut-off point of S. argusand H. subelongatusat 429 and 425 nm respectively, whereas that of H. barbouriwas located at 409 nm. Microspectrophotometry of the photoreceptors revealed that the rods of all three species contained visual pigment with the wavelength of maximum absorption (max) at approximately 500 nm. The visual pigment complement of the cones varied between the species: all possessed single cones with a maxclose to 460 nm but H. barbourialso possessed an additional class of single cone with maxat 430 nm. Three classes of visual pigment were found in the double cones, the maxbeing approximately 520, 537, and 560 nm in the two seahorses and 520, 537, and 580 nm in the pipefish. The spectral sensitivities of the syngnathids investigated here do not appear to conform to generally accepted trends for fishes inhabiting different spectral environments. The influence of the specialized feeding regime of the syngnathids is discussed in relation to our findings that ultra-violet sensitivity is apparently not necessary for zooplanktivory in certain habitats.
- Subjects
SYNGNATHIDAE; RETINOIDS; PHOTORECEPTORS; VISION; EYE movements
- Publication
Visual Neuroscience, 2007, Vol 24, Issue 3, p345
- ISSN
0952-5238
- Publication type
Article
- DOI
10.1017/S0952523807070320