title: Polarized light sensitivity and orientation in coral reef fish post-larvae.
abstract: Recent studies of the larvae of coral-reef fishes reveal that these tiny vertebrates possess remarkable swimming capabilities, as well as the ability to orient to olfactory, auditory, and visual cues. While navigation according to reef-generated chemicals and sounds can significantly affect dispersal, the effect is limited to the vicinity of the reef. Effective long-distance navigation requires at least one other capacity-the ability to maintain a bearing using, for example, a sun compass. Directional information in the sun's position can take the form of polarized-light related cues (i.e., e-vector orientation and percent polarization) and/or non-polarized-light related cues (i.e., the direct image of the sun, and the brightness and spectral gradients). We examined the response to both types of cues using commercially-reared post-larvae of the spine-cheeked anemonefish Premnas biaculeatus. Initial optomotor trials indicated that the post-larval stages are sensitive to linearly polarized light. Swimming directionality was then tested using a Drifting In-Situ Chamber (DISC), which allowed us to examine the response of the post-larvae to natural variation in light conditions and to manipulated levels of light polarization. Under natural light conditions, 28 of 29 post-larvae showed significant directional swimming (Rayleigh's test p<0.05, R = 0.74±0.23), but to no particular direction. Swimming directionality was positively affected by sky clarity (absence of clouds and haze), which explained 38% of the observed variation. Moreover, post-larvae swimming under fully polarized light exhibited a distinct behavior of tracking the polarization axis, as it rotated along with the DISC. This behavior was not observed under partially-polarized illumination. We view these findings as an indication for the use of sun-related cues, and polarized light signal in specific, by orienting coral-reef fish larvae.
authors: Department of Life Sciences, Ben-Gurion University of the Negev, Eilat Campus, Beer-Sheva, Israel ; The Interuniversity Institute for Marine Sciences of Eilat, Eilat, Israel.
authors: Igal
authors: I
authors: Berenshtein
authors: Department of Life Sciences, Ben-Gurion University of the Negev, Eilat Campus, Beer-Sheva, Israel ; The Interuniversity Institute for Marine Sciences of Eilat, Eilat, Israel.
authors: Moshe
authors: M
authors: Kiflawi
authors: Department of Life Sciences, Ben-Gurion University of the Negev, Eilat Campus, Beer-Sheva, Israel.
authors: Nadav
authors: N
authors: Shashar
authors: Department of Life Sciences, Ben-Gurion University of the Negev, Eilat Campus, Beer-Sheva, Israel.
authors: Uri
authors: U
authors: Wieler
authors: Department of Animal Sciences, The Hebrew University of Jerusalem, Rehovot, Israel.
authors: Haim
authors: H
authors: Agiv
authors: Applied Marine Physics, Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, Florida, United States of America.
authors: Claire B
authors: CB
authors: Paris
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000502:physiology*; D057894:Coral Reefs; D003463:Cues; D005399:Fishes / Q000502:physiology*; D008027:Light; D009949:Orientation / Q000502:physiology*; D013550:Swimming / Q000502:physiology