Generator Potentials in Invertebrate Photoreceptors

Fuortes, M. G. F.; O’Bryan, Paul M.

doi:10.1007/978-3-642-65340-7_7

Cited by 19 publications

(7 citation statements)

References 85 publications

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“…Early work on the photoreceptor evolution recognized that vertebrate retinal cells bear an elaborately folded cilium, while the majority of photoreceptors comprising an invertebrate's eye rely on microvillous rhabdoms. Subsequent molecular evidence has largely supported this distinction (Eakin 1963(Eakin , 1972Fuortes and O'Bryan 1972;Yau and Baylor 1989). "Ciliary" photoreceptors bear a class of opsins distinct from the opsins of rhabdomeric cells (e.g., Arendt et al 2004;Provencio et al 1998).…”

Section: Appendix 2 Phototransduction Origin and Evolutionmentioning

confidence: 46%

Opening the “Black Box”: The Genetic and Biochemical Basis of Eye Evolution

Oakley

Pankey

2008

Evo Edu Outreach

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Eyes provide a rich narrative for understanding evolution, having attracted the attention of preeminent scientists and communicators alike. Until recently, this narrative has focused primarily on the evolution of eye structure and far less on biochemistry or genetics. Although eye biochemistry was once likened to an unknown "black box;" the flood of discoveries in biochemistry is now allowing an increasingly detailed understanding of the processes involved in vision. As a result, evolutionary comparative ("tree-thinking") analyses that use these data currently allow a new and still unfolding narrative, both richer in detail and more comprehensive in scope. Rather than toppling evolutionary theory by finding irreducibly complex molecular machines, eye evolution provides detailed accounts of how natural processes tinker with existing genetic components, duplicating and recombining them, to yield complex, intricate, and highly functional eyes. Understanding the new biochemical narrative is critical for researchers and teachers alike, in order to answer antievolutionist claims, and to provide an up-to-date account of the state of knowledge on the subject of eye evolution.Keywords Evolution . Phototransduction . Vision . Eyes . Phylogeny . Novelty . ComplexityThe evolutionary history of eyes is one of the most intriguing and often-told stories in biology. It is a topic researched and discussed by members of the pantheon of evolutionists, including Darwin (1859), Salvini-Plawen and Mayr (1977), Gould (1994), andDawkins (1996). The commonly told story is familiar and has not changed much since Darwin first proposed it: A light-sensitive nerve gradually changes over evolutionary time, adding complexity across the generations. To Darwin's sketch, Salvini-Plawen and Mayr (1977) added detail, and Nilsson and Pelger (1994) tested the temporal component. The ancient canon of gradual evolution is certainly valuable for demonstrating that some assumptions are met for the hypothesis that natural selection generates complexity, serving as a colorful and graphical example (Dawkins 1996). However, this account-if taken too far-can easily be criticized, as demonstrated, for example, by proponents of Intelligent Design (ID; Behe 1996) who point out that the Darwinian canon ignores complexity at the molecular level. The structure of this article is first to briefly present the "gradual morphological" account of the evolution of eye form and to describe how this account relates to understanding evolution by natural selection. Section II will point out two primary limitations of this "gradual morphological" model, including one highlighted by ID proponents. Third, the paper will present molecular and biochemical details describing how phototransduction (the cascade of signaling events that generate a nervous impulse in response to light) and complex lenses evolved. These two case studies provide specific details about how eyes evolved. The processes elucidated, such as duplication and co-option (the use of existing components ...

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Section: Appendix 2 Phototransduction Origin and Evolutionmentioning

confidence: 46%

Opening the “Black Box”: The Genetic and Biochemical Basis of Eye Evolution

Oakley

Pankey

2008

Evo Edu Outreach

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“…Intracellular recordings from a wide variety of invertebrate photoreceptors have shown that most of these receptors depolarize when illuminated (see review by Fuortes and O'Bryan, 1972). Voltage clamp studies of Limulus ventral photoreceptors (Millecchia and Mauro, 1969b) and barnacle photoreceptors (Brown et al, 1970) have shown that in these receptors, which depolarize upon illumination, there is an increased Na + conductance in light.…”

Section: Introductionmentioning

confidence: 99%

Increased intracellular sodium mimics some but not all aspects of photoreceptor adaptation in the ventral eye of Limulus.

Fein¹,

Charlton²

1977

The Journal of General Physiology

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A B S T R A C T The effects of the intracellular iontophoretic injection of Na + ions have been quantitatively compared with adaptation in ventral photoreceptors of Limulus. We find that: (a) both light adaptation and sodium injection are associated with a decrease in the variability of the threshold response amplitude; (b) both light adaptation and sodium injection are associated with a decrease in the absolute value of the temporal dispersion of the threshold response time delay; (c) the same template curve adequately fits the intensity response relationships measured under light adaptation and Na + injection; (d) both light adaptation and Na + injection produce a fourfold decrease in response time delay for a desensitization of 3 log units; (e) the time course of light adaptation and dark adaptation is significantly faster than the onset of and recover)' from desensitization produced by Na + injection; Or) unlike local illumination, Na + injection does not produce localized desensitization of the photoreceptor. These findings suggest that a rise in intracellular Na + concentration makes at most only a minor contribution (probably less than 5%) to the total adaptation of these receptors in the intensity range we have examined (up to 3 log units above absolute threshold). However, changes in intracellular Na + concentration may contribute to certain components of light and dark adaptation in these receptors.

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“…CELL BIOLOGY © The Rockefeller University Press -0021-9525/80/05/0313/12 $1 .00 Volume 85 May 1980 [313][314][315][316][317][318][319][320][321][322][323][324] Consequently, current flow between inner and outer segment is greatest in the dark and is reduced upon exposure to light. Correspondingly, vertebrate photoreceptors (40), unlike their invertebrate counterparts (16), are partially depolarized in the dark and repolarized in light . The ionic gradients supporting these currents are thought to be maintained by Na+,K+-ATPase pumps, because the currents are abolished by ouabain (14,42,44) .…”

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confidence: 99%

[3H]ouabain autoradiography of frog retina.

Stirling¹,

Lee²

1980

The Journal of Cell Biology

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The kinetics and distribution of ouabain binding in retinas of Rana pipiens were examined quantitatively by scintillation counting and freeze-dry autoradiography . Binding within the proximal receptor layers was also nonuniform . Several peaks were observed, with those at the inner segment and synaptic layers being especially noticeable . Assuming an absence of glial cell binding in the proximal receptor layers, we calculated there to be 13 X 10 6 ouabain or Na + ,K+ pump sites per rod receptor . Limited measurements suggest a BmaX of -8 X 10-6 M for the inner plexiform layer .

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Generator Potentials in Invertebrate Photoreceptors

Cited by 19 publications

References 85 publications

Opening the “Black Box”: The Genetic and Biochemical Basis of Eye Evolution

Opening the “Black Box”: The Genetic and Biochemical Basis of Eye Evolution

Increased intracellular sodium mimics some but not all aspects of photoreceptor adaptation in the ventral eye of Limulus.

[3H]ouabain autoradiography of frog retina.

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