Retinofugal and Retinopetal Projections in the Pacific Hagfish, &lt;i&gt;Eptatretus stouti &lt;/i&gt;(Myxinoidea) (Part 2 of 2)

Wicht, Helmut; Northcutt, R. Glenn

doi:10.1159/000316087

Cited by 3 publications

(3 citation statements)

References 19 publications

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“…The Journal of Comparative Neurology | Research in Systems Neuroscience reflex of the rat pupil is controlled by the contralateral pretectum (Trejo and Cicerone, 1984). The retino-pretectal projection is also found in hagfish (Kusunoki and Amemiya, 1983;Wicht and Northcutt, 1990) and blind cave fish (Voneida and Sligar, 1976), whose retinotectal projection is mostly degenerate. Although no diencephalic projection was observed at the stages studied in our experiments (Fig.…”

Section: Visual System In Lampreys and Amphioxusmentioning

confidence: 96%

A comparative examination of neural circuit and brain patterning between the lamprey and amphioxus reveals the evolutionary origin of the vertebrate visual center

Suzuki

Murakami

Escrivà

et al. 2014

J of Comparative Neurology

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Vertebrates are equipped with so-called camera eyes, which provide them with image-forming vision. Vertebrate image-forming vision evolved independently from that of other animals and is regarded as a key innovation for enhancing predatory ability and ecological success. Evolutionary changes in the neural circuits, particularly the visual center, were central for the acquisition of image-forming vision. However, the evolutionary steps, from protochordates to jaw-less primitive vertebrates and then to jawed vertebrates, remain largely unknown. To bridge this gap, we present the detailed development of retinofugal projections in the lamprey, the neuroarchitecture in amphioxus, and the brain patterning in both animals. Both the lateral eye in larval lamprey and the frontal eye in amphioxus project to a light-detecting visual center in the caudal prosencephalic region marked by Pax6, which possibly represents the ancestral state of the chordate visual system. Our results indicate that the visual system of the larval lamprey represents an evolutionarily primitive state, forming a link from protochordates to vertebrates and providing a new perspective of brain evolution based on developmental mechanisms and neural functions.

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Section: Visual System In Lampreys and Amphioxusmentioning

confidence: 96%

A comparative examination of neural circuit and brain patterning between the lamprey and amphioxus reveals the evolutionary origin of the vertebrate visual center

Suzuki

Murakami

Escrivà

et al. 2014

J of Comparative Neurology

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“…Alternatively, the retinal transmitters may be nonfunctional, and the components are under no direct selective pressure but persist because of the selection for some other character, as proposed for retinofugal and retinopetal connections in the myxinoid Epatretus stouti. This hagfish has eyes lacking a lense and iris and, as in Ichthyophis, the only visually guided behavior is negative phototaxis (Wicht and Northcutt 1990). Alternatively, the caecilian eye might perform other, probably regulatory, tasks.…”

Section: Discussionmentioning

confidence: 99%

Development and organization of the retinal dopaminergic system of Ichthyophis kohtaoensis (Amphibia; Gymnophiona)

Dünker

1997

Cell and Tissue Research

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Ichthyophis kohtaoensis, a member of the limbless Gymnophiona, has a specialized subterranean burrowing mode of life and a predominantly olfactory-guided orientation. The only visually guided behavior seems to be negative phototaxis. As these animals possess extremely small eyes (only 540 microm in diameter in adults), functional investigations of single retinal cells by electrophysiological methods have so far failed. Therefore, the content and distribution of retinal transmitters have been investigated as indications for a functioning sense organ in an animal that is supposed to be blind. In this study, the organization and development of the dopaminergic system have been examined in the retinae of embryonic, larval, and adult I. kohtaoensis, by using an antiserum against tyrosine hydroxylase, the rate-limiting enzyme in the catecholamine synthetic pathway, and an antiserum against dopamine itself. Labeled somata are situated in the inner nuclear layer and in the ganglion cell layer. Dopamine-positive fibers form a dense diffuse plexus, that covers the whole inner plexiform layer, whereas tyrosine hydroxylase-immunoreactive processes show a tendency to arborize in a stratified manner. Tyrosine-hydroxylase-immunolabeled fibers can occasionally be observed in the optic nerve head of larval stages. During ontogenesis and larval development, the distribution of transmitter-expressing cells changes and their number decreases, but no general degeneration of the visual system is detectable. Adult Ichthyophis still have retinal transmitters, indicating that the eyes, although obviously playing a minor role in a subterranean ecological niche, retain all the elements of functioning sense organs.

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“…Thus, by analogy, one would not expect the complete reduction of the lens in Eptatretus if this were a case of degenerative evolution. (For additional arguments, both for and against, see Fernholm 1975;Wicht & Northcutt 1990).…”

Section: (A) the Len S P La C O D Ementioning

confidence: 99%

Ontogeny of the head of the Pacific hagfish ( Eptatretus stouti , Myxinoidea): development of the lateral line system

Wicht

1995

Phil. Trans. R. Soc. Lond. B

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The head of adult hagfishes (jawless craniates, Myxinoidea) of the family Eptatretidae displays a number of skin grooves of uncertain origin. These grooves have been homologized to the neuromast lines of other craniates, and they are innervated by two ganglionated cranial nerves that have been interpreted as lateral line nerves. The grooves do not, however, contain the compound receptors that are typical of a lateral line (i.e. neuromasts or electroreceptors), and both their development and function have remained enigmatic. To elucidate the embryonic origin of the grooves (which should develop from placodes if they are homologues of the lateral line system), embryos of Pacific hagfish were examined by means of three-dimensional reconstructions from serial sections. Because of the scarcity of specimens of embryonic hagfishes, only two embryos were reconstructed, but these reconstructions clearly show that a number of placodes and placodal derivatives (i.e. sensory ridges, receptor primordia, and cranial ganglia) occur in the head of embryonic eptatretid hagfishes. Some of these placodes correspond to the lens and epibranchial placodes of other craniates, but there are also three other placodes which represent possible homologues of lateral line placodes. The topology of the placodes in this latter group corresponds to the topology of the grooves of adult hagfishes, and we therefore reach three conclusions: (i) that an embryonic lateral line system is present in hagfishes; (ii) that the grooves of adult hagfishes in all probability derive from lateral line placodes; and (iii) that the presence of lateral line placodes is a primitive character of craniates.

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Retinofugal and Retinopetal Projections in the Pacific Hagfish, <i>Eptatretus stouti </i>(Myxinoidea) (Part 2 of 2)

Cited by 3 publications

References 19 publications

A comparative examination of neural circuit and brain patterning between the lamprey and amphioxus reveals the evolutionary origin of the vertebrate visual center

A comparative examination of neural circuit and brain patterning between the lamprey and amphioxus reveals the evolutionary origin of the vertebrate visual center

Development and organization of the retinal dopaminergic system of Ichthyophis kohtaoensis (Amphibia; Gymnophiona)

Ontogeny of the head of the Pacific hagfish ( Eptatretus stouti , Myxinoidea): development of the lateral line system

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