Larval and adult visual pigments of the zebrafish, Brachydanio rerio

149

185

SUMMARY Zebrafish have two red, LWS-1 and LWS-2, and four green, RH2-1, RH2-2, RH2-3 and RH2-4, opsin genes encoding photopigments with distinct absorption spectra. Occurrence of opsin subtypes by gene duplication is characteristic of fish but little is known whether the subtypes are expressed differently in the retina, either spatially or temporally. Here we show by in situ hybridization the dynamic expression patterns of the opsin subtypes in the zebrafish retina. Expression of red type opsins is initiated with the shorter-wavelength subtype LWS-2, followed by the longer-wavelength subtype LWS-1. In the adult retina, LWS-2 was expressed in the central to dorsal area and LWS-1 in the ventral and peripheral areas. Expression patterns of green type opsins were similar to those of the red type opsins. The expression started with the shortest wavelength subtype RH2-1 followed by the longer wavelength ones, and in the adult retina, the shorter wavelength subtypes (RH2-1 and RH2-2) were expressed in the central to dorsal area and longer wavelength subtypes (RH2-3 and RH2-4)in the ventral and peripheral areas. These results provide the framework for subsequent studies of opsin gene regulation and for probing functional rationale of the developmental changes by using the power of zebrafish genetics.

Section: Discussionsupporting

confidence: 80%

Section: In Situ Hybridization (Ish)mentioning

confidence: 99%

Temporal and spatial changes in the expression pattern of multiple red and green subtype opsin genes during zebrafish development

Takechi

Kawamura

2005

149

185

“…While a ∼496 nm peak corresponding to Rh1-2 was not detected in previous microspectrophotometry studies, which could have helped to localize expression at the cellular level (Nawrocki et al, 1985;Robinson et al, 1993;Cameron, 2002), this is likely the result of either a lack of sensitivity to detect the poorly expressing opsin or confounding signals with other opsins that have similar λ max values, such as rhodopsin, Rh2-3 or Rh2-4 (Chinen et al, 2003). Interestingly, the expression pattern of rh1-2 most resembles that of rh2-3 and rh2-4, which is confined to peripheral photoreceptors near the CMZ in embryos and juveniles (Takechi and Kawamura, 2005).…”

Section: Discussionmentioning

confidence: 72%

A second visual rhodopsin gene,rh1-2, is expressed in zebrafish photoreceptors and found in other ray-finned fishes

Morrow

Lazic

Fox

et al. 2016

Rhodopsin (rh1) is the visual pigment expressed in rod photoreceptors of vertebrates that is responsible for initiating the critical first step of dim-light vision. Rhodopsin is usually a single copy gene; however, we previously discovered a novel rhodopsin-like gene expressed in the zebrafish retina, rh1-2, which we identified as a functional photosensitive pigment that binds 11-cis retinal and activates in response to light. Here, we localized expression of rh1-2 in the zebrafish retina to a subset of peripheral photoreceptor cells, which indicates a partially overlapping expression pattern with rh1. We also expressed, purified and characterized Rh1-2, including investigation of the stability of the biologically active intermediate. Using fluorescence spectroscopy, we found the half-life of the rate of retinal release of Rh1-2 following photoactivation to be more similar to that of the visual pigment rhodopsin than to the non-visual pigment exo-rhodopsin (exorh), which releases retinal around 5 times faster. Phylogenetic and molecular evolutionary analyses show that rh1-2 has ancient origins within teleost fishes, is under similar selective pressure to rh1, and likely experienced a burst of positive selection following its duplication and divergence from rh1. These findings indicate that rh1-2 is another functional visual rhodopsin gene, which contradicts the prevailing notion that visual rhodopsin is primarily found as a single copy gene within ray-finned fishes. The reasons for retention of this duplicate gene, as well as possible functional consequences for the visual system, are discussed.

“…The filter only permitted wavelengths above 800nm to pass through, which we can detect using our IR-sensitive camera, but the zebrafish cannot (Nawrocki et al, 1985). In addition, the entire setup was shielded from light using thick black fabric and experiments were conducted in a dark room.…”

Section: High-speed Behavioral Recordingsmentioning

confidence: 99%

Visually guided gradation of prey capture movements in larval zebrafish

Patterson

Abraham

MacIver

et al. 2013

107

155

SUMMARYA mechanistic understanding of goal-directed behavior in vertebrates is hindered by the relative inaccessibility and size of their nervous systems. Here, we have studied the kinematics of prey capture behavior in a highly accessible vertebrate model organism, the transparent larval zebrafish (Danio rerio), to assess whether they use visual cues to systematically adjust their movements. We found that zebrafish larvae scale the speed and magnitude of turning movements according to the azimuth of one of their standard prey, paramecia. They also bias the direction of subsequent swimming movements based on prey azimuth and select forward or backward movements based on the prey's direction of travel. Once within striking distance, larvae generate either ram or suction capture behaviors depending on their distance from the prey. From our experimental estimations of ocular receptive fields, we ascertained that the ultimate decision to consume prey is likely a function of the progressive vergence of the eyes that places the target in a proximal binocular 'capture zone'. By repeating these experiments in the dark, we demonstrate that paramecia are only consumed if they contact the anterior extremities of larvae, which triggers ocular vergence and tail movements similar to close proximity captures in lit conditions. These observations confirm the importance of vision in the graded movements we observe leading up to capture of more distant prey in the light, and implicate somatosensation in captures in the absence of light. We discuss the implications of these findings for future work on the neural control of visually guided behavior in zebrafish. Supplementary material available online at