Abstract:Besides colour and intensity, some invertebrates are able to independently detect the polarization of light. Among vertebrates, such separation of visual modalities has only been hypothesized for some species of anchovies whose cone photoreceptors have unusual ultrastructure that varies with retinal location. Here, I tested this hypothesis by performing physiological experiments of colour and polarization discrimination using the northern anchovy, Optic nerve recordings showed that the ventro-temporal (VT), bu… Show more
“…Strikingly, functionally specialized ommatidial subtypes could be distributed randomly (as in the case of Drosophila ), or in alternating rows (as shown for Dolichopodidae )—two fundamentally different design principles that could be viewed as alternative solutions for spatially separating these inputs without sacrificing too much of the visual field to either one modality (while neglecting the other). Interestingly, similar segregation of color- and polarization sensitive pathways has recently been proposed for a vertebrate retina (Novales Flamarique, 2017 ).…”
Section: Neural Circuits Connecting To Specific Ommatidial Subtypes—lsupporting
The e-vector orientation of linearly polarized light represents an important visual stimulus for many insects. Especially the detection of polarized skylight by many navigating insect species is known to improve their orientation skills. While great progress has been made towards describing both the anatomy and function of neural circuit elements mediating behaviors related to navigation, relatively little is known about how insects perceive non-celestial polarized light stimuli, like reflections off water, leaves, or shiny body surfaces. Work on different species suggests that these behaviors are not mediated by the “Dorsal Rim Area” (DRA), a specialized region in the dorsal periphery of the adult compound eye, where ommatidia contain highly polarization-sensitive photoreceptor cells whose receptive fields point towards the sky. So far, only few cases of polarization-sensitive photoreceptors have been described in the ventral periphery of the insect retina. Furthermore, both the structure and function of those neural circuits connecting to these photoreceptor inputs remain largely uncharacterized. Here we review the known data on non-celestial polarization vision from different insect species (dragonflies, butterflies, beetles, bugs and flies) and present three well-characterized examples for functionally specialized non-DRA detectors from different insects that seem perfectly suited for mediating such behaviors. Finally, using recent advances from circuit dissection in Drosophila melanogaster, we discuss what types of potential candidate neurons could be involved in forming the underlying neural circuitry mediating non-celestial polarization vision.
“…Strikingly, functionally specialized ommatidial subtypes could be distributed randomly (as in the case of Drosophila ), or in alternating rows (as shown for Dolichopodidae )—two fundamentally different design principles that could be viewed as alternative solutions for spatially separating these inputs without sacrificing too much of the visual field to either one modality (while neglecting the other). Interestingly, similar segregation of color- and polarization sensitive pathways has recently been proposed for a vertebrate retina (Novales Flamarique, 2017 ).…”
Section: Neural Circuits Connecting To Specific Ommatidial Subtypes—lsupporting
The e-vector orientation of linearly polarized light represents an important visual stimulus for many insects. Especially the detection of polarized skylight by many navigating insect species is known to improve their orientation skills. While great progress has been made towards describing both the anatomy and function of neural circuit elements mediating behaviors related to navigation, relatively little is known about how insects perceive non-celestial polarized light stimuli, like reflections off water, leaves, or shiny body surfaces. Work on different species suggests that these behaviors are not mediated by the “Dorsal Rim Area” (DRA), a specialized region in the dorsal periphery of the adult compound eye, where ommatidia contain highly polarization-sensitive photoreceptor cells whose receptive fields point towards the sky. So far, only few cases of polarization-sensitive photoreceptors have been described in the ventral periphery of the insect retina. Furthermore, both the structure and function of those neural circuits connecting to these photoreceptor inputs remain largely uncharacterized. Here we review the known data on non-celestial polarization vision from different insect species (dragonflies, butterflies, beetles, bugs and flies) and present three well-characterized examples for functionally specialized non-DRA detectors from different insects that seem perfectly suited for mediating such behaviors. Finally, using recent advances from circuit dissection in Drosophila melanogaster, we discuss what types of potential candidate neurons could be involved in forming the underlying neural circuitry mediating non-celestial polarization vision.
“…As opposed to the retinal photoreceptors found in invertebrates, which differentially absorb naturally incident light on the retina as a function of polarization 2–4 , a phenomenon known as axial dichroism, those of vertebrates have no equivalent preferred axial absorbance. As such, polarization sensitivity in vertebrates, except in a group of anchovies in the family Engraulididae 5–9 , does not have a demonstrated mechanistic foundation at the photoreceptor level and is highly controversial 10 . An exception to the lack of axial dichroism of vertebrate photoreceptors is found in the retinas of anchovies 11 .…”
Section: Introductionmentioning
confidence: 99%
“…Other areas of the retina in the northern anchovy have cones with regular lamellar disposition, i.e., transverse to the length of the cell 12 . The two types of axially dichroic cones house a middle wavelength sensitive visual pigment with statistically similar wavelength of maximum absorbance (λ max ) 10,13 . The remainder of the retina has at least two visual pigments among the cone population with λ max in the middle and long wavelength regions of the spectrum 10,13 .Figure 1Characteristics of the anchovy retina and illustrations of prey capture behaviour and measured variables.…”
Section: Introductionmentioning
confidence: 99%
“…The two types of axially dichroic cones house a middle wavelength sensitive visual pigment with statistically similar wavelength of maximum absorbance (λ max ) 10,13 . The remainder of the retina has at least two visual pigments among the cone population with λ max in the middle and long wavelength regions of the spectrum 10,13 .Figure 1Characteristics of the anchovy retina and illustrations of prey capture behaviour and measured variables. ( a ) Retinal flat mount superimposed on the head of a northern anchovy showing the polarization-sensitive area in the ventro-temporal retina with axially dichroic cones.…”
Section: Introductionmentioning
confidence: 99%
“…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 .…”
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.
The retinas of non-mammalian vertebrates have cone photoreceptor mosaics that are often organized as highly patterned lattice-like distributions. In fishes, the two main lattice-like patterns are composed of double cones and single cones that are either assembled as interdigitized squares or as alternating rows. The functional significance of such orderly patterning is unknown. Here, the cone mosaics in two species of Soleidae flatfishes, the common sole and the Senegalese sole, were characterized and compared to those from other fishes to explore variability in cone patterning and how it may relate to visual function..The cone mosaics of the common sole and the Senegalese sole consisted of single, double and triple cones in formations that differed from the traditional square mosaic pattern reported for other flatfishes in that no evidence of higher order periodicity was present. Furthermore, mean regularity indices for single and double cones were conspicuously lower than those of other fishes with "typical" square and row mosaics, but comparable to those of goldfish, a species with lattice-like periodicity in its cone mosaic. Opsin transcripts detected by qPCR (sws1, sws2, rh2.3, rh2.4, lws, and rh1) were uniformly expressed
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