Multifocal optical systems and pupil dynamics in birds

Lind, Olle; Kelber, Almut; Kröger, Ronald H. H.

doi:10.1242/jeb.018630

Cited by 46 publications

(49 citation statements)

References 45 publications

(61 reference statements)

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“…Blue tits have multifocal optics, which correct for chromatic aberration and improve colour vision more efficiently than monofocal optics (Lind et al, 2008). Relating eye size to body mass and time of singing onset, Thomas et al (Thomas et al, 2002) find that passerines with larger than expected eye size start singing earlier and have a greater visual performance.…”

Section: Resultsmentioning

confidence: 99%

The intensity threshold of colour vision in a passerine bird, the blue tit

Gomez

Grégoire

Granado

et al. 2014

Journal of Experimental Biology

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Many vertebrates use colour vision for vital behaviour but their visual performance in dim light is largely unknown. The light intensity threshold of colour vision is known only for humans, horses and two parrot species. Here, we first explore this threshold in a passerine bird, the blue tit (Cyanistes caeruleus). Using classic conditioning of colour cues to food rewards in three individuals, we find a threshold ranging from 0.05 to 0.2 cd m −2. Results are comparable to the two previously tested bird species. For tits, nest light conditions probably exceed that threshold, at least after sunrise. These results shed new light on the lively debate questioning the visual performance of cavity nesters and the evolutionary significance of egg and chick coloration. Although this needs further investigation, it is possible that blue tits exploit both colour and brightness cues when viewing their eggs, chicks or conspecifics in their nests.

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Section: Resultsmentioning

confidence: 99%

The intensity threshold of colour vision in a passerine bird, the blue tit

Gomez

Grégoire

Granado

et al. 2014

Journal of Experimental Biology

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“…Nevertheless, the largest birds, including cranes and ratites (ostriches and emus) are VS, consistent with their very large eyes (Wright and Bowmaker, 2001; Ödeen and Håstad, 2013; Porter et al, 2014). A potential solution to the chromatic aberration challenge that UV sensitivity imposes is the use of multifocal lenses in many avian species (Lind et al, 2008). Such lenses have the ability to focus both short-and medium-wavelength images simultaneously.…”

Section: Management Of Chromatic Aberration In Vertebratesmentioning

confidence: 93%

Photoreception and vision in the ultraviolet

Cronin

Bok

2016

Journal of Experimental Biology

148

128

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Ultraviolet (UV) light occupies the spectral range of wavelengths slightly shorter than those visible to humans. Because of its shorter wavelength, it is more energetic (and potentially more photodamaging) than 'visible light', and it is scattered more efficiently in air and water. Until 1990, only a few animals were recognized as being sensitive to UV light, but we now know that a great diversity, possibly even the majority, of animal species can visually detect and respond to it. Here, we discuss the history of research on biological UV photosensitivity and review current major research trends in this field. Some animals use their UV photoreceptors to control simple, innate behaviors, but most incorporate their UV receptors into their general sense of vision. They not only detect UV light but recognize it as a separate color in light fields, on natural objects or living organisms, or in signals displayed by conspecifics. UV visual pigments are based on opsins, the same family of proteins that are used to detect light in conventional photoreceptors. Despite some interesting exceptions, most animal species have a single photoreceptor class devoted to the UV. The roles of UV in vision are manifold, from guiding navigation and orientation behavior, to detecting food and potential predators, to supporting high-level tasks such as mate assessment and intraspecific communication. Our current understanding of UV vision is restricted almost entirely to two phyla: arthropods and chordates (specifically, vertebrates), so there is much comparative work to be done.

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“…R. Soc. B 283: 20161063 optical systems that compensate somewhat for longitudinal chromatic aberration through concentric zones of varying refractive power [61,62]. It is interesting to note, however, that while the ostrich appears to possess a multifocal optical system, the emu has a monofocal optical system, despite an apparently similar complement of photoreceptors [62].…”

Section: Discussionmentioning

confidence: 99%

Visual pigments in a palaeognath bird, the emuDromaius novaehollandiae: implications for spectral sensitivity and the origin of ultraviolet vision

et al. 2016

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A comprehensive description of the spectral characteristics of retinal photoreceptors in palaeognaths is lacking. Moreover, controversy exists with respect to the spectral sensitivity of the short-wavelength-sensitive-1 (SWS1) opsin-based visual pigment expressed in one type of single cone: previous microspectrophotometric (MSP) measurements in the ostrich (Struthio camelus) suggested a violet-sensitive (VS) SWS1 pigment, but all palaeognath SWS1 opsin sequences obtained to date (including the ostrich) imply that the visual pigment is ultraviolet-sensitive (UVS). In this study, MSP was used to measure the spectral properties of visual pigments and oil droplets in the retinal photoreceptors of the emu (Dromaius novaehollandiae). Results show that the emu resembles most other bird species in possessing four spectrally distinct single cones, as well as double cones and rods. Four cone and a single rod opsin are expressed, each an orthologue of a previously identified pigment. The SWS1 pigment is clearly UVS (wavelength of maximum absorbance [l max ] ¼ 376 nm), with key tuning sites (Phe86 and Cys90) consistent with other vertebrate UVS SWS1 pigments. Palaeognaths would appear, therefore, to have UVS SWS1 pigments. As they are considered to be basal in avian evolution, this suggests that UVS is the most likely ancestral state for birds. The functional significance of a dedicated UVS cone type in the emu is discussed.

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Multifocal optical systems and pupil dynamics in birds

Cited by 46 publications

References 45 publications

The intensity threshold of colour vision in a passerine bird, the blue tit

The intensity threshold of colour vision in a passerine bird, the blue tit

Photoreception and vision in the ultraviolet

Visual pigments in a palaeognath bird, the emuDromaius novaehollandiae: implications for spectral sensitivity and the origin of ultraviolet vision

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