Variation in opsin transcript expression explains intraretinal differences in spectral sensitivity of the northern anchovy

Journal of Fish Biology

2018

Colour vision is mediated by the expression of different visual pigments in photoreceptors of the vertebrate retina. Each visual pigment is a complex of a protein (opsin) and a vitamin A chromophore; alterations to either component affects visual pigment absorbance and, potentially, the visual capabilities of an animal. Many species of fish undergo changes in opsin expression during retinal development. In the case of salmonid fishes the single cone photoreceptors undergo a switch in opsin expression from SWS1 (ultraviolet sensitive) to SWS2 (blue‐light sensitive) starting at the yolk‐sac alevin stage, around the time when they first experience light. Whether light may initiate this event or produce a plastic response in the various photoreceptors is unknown. In this study, Chinook salmon Oncorhynchus tshawytscha were exposed to light from the embryonic (5 days prior to hatching) into the yolk sac alevin (25 days post hatching) stage and the spectral phenotype of photoreceptors assessed with respect to that of unexposed controls by in situ hybridization with opsin riboprobes. Light exposure did not change the spectral phenotype of photoreceptors, their overall morphology or spatial arrangement. These results concur with those from a variety of fish species and suggest that plasticity in photoreceptor spectral phenotype via changes in opsin expression may not be a widespread occurrence among teleosts.

Section: Discussionsupporting

confidence: 91%

Light exposure during embryonic and yolk‐sac alevin development of Chinook salmon Oncorhynchus tshawytscha does not alter the spectral phenotype of photoreceptors

Journal of Fish Biology

2018

“…Colour vision requires the activation of at least two retinal photoreceptor types, each expressing a different predominant visual pigment . A visual pigment is a molecular complex consisting of a protein (opsin) and a chromophore (retinal, the aldehyde of vitamin A 1 , or 3,4‐dehydroretinal, the aldehyde of vitamin A 2 ); alteration to either component changes the absorbance of the photoreceptor and, potentially, the spectral (colour) sensitivity of the animal . There are five main groups of vertebrate visual opsins, most sensitive to either ultraviolet (UV) light (SWS1 opsin gene family), short wavelength or blue light (SWS2 opsin gene family), middle wavelength or green light (MWS, RH1 and RH2 opsin gene families) or long wavelength or red light (LWS opsin gene family) .…”

Section: Introductionmentioning

confidence: 99%

“…2,3 Many vertebrates express multiple opsins within a photoreceptor [7][8][9][10][11] and some can modulate the primary opsin expressed within individual photoreceptor types during development. 7,9,[12][13][14][15][16][17][18][19] In rodents, 13,20,21 human organoids 22 and fishes, [23][24][25][26] this regulation involves the action of thyroid hormone (3,5,3′-triiodothyronine, T 3 , or l-thyroxine, T 4 ) binding to thyroid hormone receptors (TRβs or, potentially, TRαs 24 ), with T 3 itself being locally regulated in the retina of some species through the action of deiodinase enzymes. 22,26,27 In salmonid fishes, treatment of the holding water with T 4 induces an opsin switch from SWS1 to SWS2 in the single cone photoreceptors, transforming them from UV to short wavelength sensitive (S) cones.…”

mentioning

confidence: 99%

Growth hormone regulates opsin expression in the retina of a salmonid fish

Ahmed

Cheng

et al. 2019

J Neuroendocrinology

Colour vision relies on retinal photoreceptors that express a different predominant visual pigment protein (opsin). In several vertebrates, the primary opsin expressed by a photoreceptor can change throughout ontogeny, although the molecular factors that influence such regulation are poorly understood. One of these factors is thyroid hormone which, together with its receptors, modulates opsin expression in the retinas of multiple vertebrates including rodents and salmonid fishes. In the latter, thyroid hormone induces a switch in opsin expression from SWS1 (ultraviolet light sensitive) to SWS2 (short wavelength or blue light sensitive) in the single cone photoreceptors of the retina. The actions of other hormones on opsin expression have not been investigated. In the present study, we used a transgenic strain of coho salmon (Oncorhynchus kitsutch) with enhanced levels of circulating growth hormone compared to that of wild siblings to assess the effects of this hormone on the SWS1 to SWS2 opsin switch. Transgenic fish showed a developmentally accelerated opsin switch compared to size‐matched controls as assessed by immunohistological and in situ hybridisation labelling of photoreceptors and by quantification of transcripts using quantitative polymerase chain reaction. This accelerated switch led to a different spectral sensitivity maximum, under a middle to long wavelength adapting background, from ultraviolet (λmax ~ 380 nm) in controls to short wavelengths (λmax ~ 430 nm) in transgenics, demonstrating altered colour vision. The effects of growth hormone over‐expression were independent of circulating levels of thyroid hormone (triiodothyronine), the hormone typically associated with opsin switches in vertebrates.

“…In the northern anchovy, Engraulis mordax , optic nerve recordings show that the ventro-temporal area of the retina comprising axially dichroic cones exhibits polarization sensitivity but lacks colour sensitivity, as judged by a single peak, at 520 nm, spectral sensitivity function 10 . The rest of the retina shows a two peak spectral sensitivity function, at 500 nm and 540 nm, suggesting colour discrimination 10,14 . The spectral sensitivity findings are in accord with the number of visual pigments and the distribution of opsin transcripts in the retina 14 .…”

Section: Introductionmentioning

confidence: 99%

“…The rest of the retina shows a two peak spectral sensitivity function, at 500 nm and 540 nm, suggesting colour discrimination 10,14 . The spectral sensitivity findings are in accord with the number of visual pigments and the distribution of opsin transcripts in the retina 14 . In essence, the retina of the northern anchovy is structurally and functionally divided for polarization and colour vision in analogy with the retina of multiple insect species and stomatopods 2 .…”

Section: Introductionmentioning

confidence: 99%

Swimming behaviour tunes fish polarization vision to double prey sighting distance

2019

Sci Rep

Self Cite

The analysis of the polarization of light expands vision beyond the realm of colour and intensity and is used for multiple ecological purposes among invertebrates including orientation, object recognition, and communication. How vertebrates use polarization vision as part of natural behaviours is widely unknown. In this study, I tested the hypothesis that polarization vision improves the detection of zooplankton prey by the northern anchovy, Engraulis mordax, the only vertebrate with a demonstrated photoreceptor basis explaining its polarization sensitivity. Juvenile anchovies were recorded free foraging on zooplankton under downwelling light fields of varying percent polarization (98%, 67%, 19%, and 0% - unpolarized light). Analyses of prey attack sequences showed that anchovies swam in the horizontal plane perpendicular, on average, to the polarization direction of downwelling light and attacked prey at pitch angles that maximized polarization contrast perception of prey by the ventro-temporal retina, the area devoted to polarization vision in this animal. Consequently, the mean prey location distance under polarized light was up to 2.1 times that under unpolarized conditions. All indicators of polarization vision mediated foraging were present under 19% polarization, which is within the polarization range commonly found in nature during daylight hours. These results demonstrate: (i) the first use of oriented swimming for enhancing polarization contrast detection of prey, (ii) its relevance to improved foraging under available light cues in nature, and (iii) an increase in target detection distance that is only matched by polarization based artificial systems.