A Cambrian origin for vertebrate rods

Asteriti, Sabrina; Grillner, Sten; Cangiano, Lorenzo

doi:10.7554/elife.07166

Cited by 43 publications

(66 citation statements)

References 83 publications

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“…B and D ), which is accelerated much as in real light (Figs C and C ). Our experiments support and extend those of Asteriti and colleagues (), who also observed recovery of sensitivity in bleached lamprey photoreceptors after treatment with exogenous chromophore.…”

Section: Discussionsupporting

confidence: 92%

“…In darkness, both lamprey and mouse rods have responses to single photons of similar amplitude (Morshedian & Fain, ; Asteriti et al . ) and response–intensity curves of similar shape (Fig. A and Woodruff et al .…”

Section: Discussionsupporting

confidence: 66%

“…Lamprey rods respond to single photons with a sensitivity not very different from mouse and are about 75–100 times more sensitive than lamprey or mouse cones (see also Asteriti et al . ).…”

Section: Introductionmentioning

confidence: 97%

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Light adaptation and the evolution of vertebrate photoreceptors

Morshedian

Fain

2017

The Journal of Physiology

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The earliest vertebrates were agnathans - fish-like organisms without jaws, which first appeared near the end of the Cambrian radiation. One group of agnathans became cyclostomes, which include lamprey and hagfish. Other agnathans gave rise to jawed vertebrates or gnathostomes, the group including all other existing vertebrate species. Because cyclostomes diverged from other vertebrates 500 million years ago, it may be possible to infer some of the properties of the retina of early vertebrate progenitors by comparing lamprey to other vertebrates. We have previously shown that rods and cones in lamprey respond to light much like photoreceptors in other vertebrates and have a similar sensitivity. We now show that these affinities are even closer. Both rods and cones adapt to background light and to bleaches in a manner almost identical to other vertebrate photoreceptors. The operating range in darkness is nearly the same in lamprey and in amphibian or mammalian rods and cones; moreover background light shifts response-intensity curves downward and to the right over a similar range of ambient intensities. Rods show increment saturation at about the same intensity as mammalian rods, and cones never saturate. Bleaches decrease sensitivity in part by loss of quantum catch and in part by opsin activation of transduction. These correspondences are so numerous and pervasive that they are unlikely to result from convergent evolution but argue instead that early vertebrate progenitors of both cyclostomes and mammals had photoreceptors much like our own.

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Section: Discussionsupporting

confidence: 92%

Section: Discussionsupporting

confidence: 66%

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Light adaptation and the evolution of vertebrate photoreceptors

Morshedian

Fain

2017

The Journal of Physiology

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“…32 One class of lamprey photoreceptor expresses rhodopsin and exhibits comparable sensitivity to gnathostome rods, 33,34 despite exhibiting cone-like morphology. However, there have not yet been reports to indicate whether the lamprey retina has the ability to operate in a photon-processing mode.…”

Section: Evolution Of Rods and Single-photon Processingmentioning

confidence: 99%

Why rods and cones?

Lamb

2015

Eye

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Under twenty-first-century metropolitan conditions, almost all of our vision is mediated by cones and the photopic system, yet cones make up barely 5% of our retinal photoreceptors. This paper looks at reasons why we additionally possess rods and a scotopic system, and asks why rods comprise 95% of our retinal photoreceptors. It considers the ability of rods to reliably signal the arrival of individual photons of light, as well as the ability of the retina to process these singlephoton signals, and it discusses the advantages that accrue. Drawbacks in the arrangement, including the very slow dark adaptation of scotopic vision, are also considered. Finally, the timing of the evolution of cone and rod photoreceptors, the retina, and the camera-style eye is summarised.

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“…Recent electrophysiological studies conducted on the rod photoreceptors of the sea lamprey, Petromyzon marinus (Morshedian and Fain, 2015), and the European river lamprey, Lampetra fluviatilis (Asteriti et al, 2015), however, demonstrate their ability to detect single photons of light, confirming true rod functionality in lampreys (Baylor, 1987;Baylor et al, 1979).…”

Section: Characterising the Photoreceptor Typementioning

confidence: 99%

Retinal temporal resolution and contrast sensitivity in the parasitic lampreyMordacia mordaxand its non-parasitic derivativeM.praecox

Warrington

Hart

Potter

et al. 2017

Journal of Experimental Biology

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Lampreys and hagfishes are the sole extant representatives of the early agnathan ( jawless) vertebrates. We compared retinal function of fully metamorphosed, immature Mordacia mordax (which are about to commence parasitic feeding) with those of sexually mature individuals of its non-parasitic derivative M. praecox. We focused on elucidating the retinal adaptations to dim-light environments in these nocturnally active lampreys, using electroretinography to determine the temporal resolution (flicker fusion frequency, FFF) and temporal contrast sensitivity of enucleated eyecups at different temperatures and light intensities. FFF was significantly affected by temperature and light intensity. Critical flicker fusion frequency (cFFF, the highest FFF recorded) of M. praecox and M. mordax increased from 15.1 and 21.8 Hz at 9°C to 31.1 and 36.9 Hz at 24°C, respectively. Contrast sensitivity of both species increased by an order of magnitude between 9 and 24°C, but remained comparatively constant across all light intensities. Although FFF values for Mordacia spp. are relatively low, retinal responses showed a particularly high contrast sensitivity of 625 in M. praecox and 710 in M. mordax at 24°C. This suggests selective pressures favour low temporal resolution and high contrast sensitivity in both species, thereby enhancing the capture of photons and increasing sensitivity in their light-limited environments. FFF indicated all retinal photoreceptors exhibit the same temporal response. Although the slow response kinetics (i.e. low FFF) and saturation of the response at bright light intensities characterise the photoreceptors of both species as rod-like, it is unusual for such a photoreceptor to be functional under scotopic and photopic conditions.

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A Cambrian origin for vertebrate rods

Cited by 43 publications

References 83 publications

Light adaptation and the evolution of vertebrate photoreceptors

Light adaptation and the evolution of vertebrate photoreceptors

Why rods and cones?

Retinal temporal resolution and contrast sensitivity in the parasitic lampreyMordacia mordaxand its non-parasitic derivativeM.praecox

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