The Functional Organization of the Nervous System of Enteropneusta

Bullock, Theodore H.

doi:10.2307/1537832

Cited by 61 publications

(60 citation statements)

References 15 publications

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“…These data clearly demonstrate similar relative expression of transcription factors with critical roles in anteroposterior patterning between chordates and hemichordates. Although most comparative studies and speculations on the nervous system of hemichordates have focused on the dorsal and ventral axon tracts as potential homologues of chordate central neural structures, the results from this study suggest, as was proposed by Bullock in 1945, that the appropriate comparison is with the entire net. The cords are probably local thickenings of the nerve plexus rather than integrative centres (Dilly et al 1970).…”

Section: Anteroposterior Patterning In Hemichordatesmentioning

confidence: 61%

“…Figure 1 outlines some of the main anatomical features of enteropneusts and shows a photomicrograph of a juvenile worm of the harrimaniid Saccoglossus kowalevskii: the tripartite body plan is divided into an anterior prosome or proboscis, a mesosome or collar and a metasome or trunk. The proboscis is muscular, ciliated and highly innervated with sensory neurons (Bullock 1945;Knight-Jones 1952), and its primary functions are digging and feeding. The mouth opens up on the ventral side and marks the boundary between the proboscis and the collar.…”

Section: Problems Reconstructing Ancestral Deuterostome Charactersmentioning

confidence: 99%

“…The organization of the nerve net is based around a broad distribution of cell bodies throughout the ectoderm. Despite the general diffuse organization of the nervous system, there is a significant dorsoventral and anteroposterior polarity in its structure and organization, particularly in the dorsoventral dimension (Bullock 1945;Knight-Jones 1952). A mat of axons spreads out along the basement membrane, which is thickened in certain areas of the ectoderm, at the base of the proboscis, along the anterodorsal region of the body in the mesosome and in both the dorsal and ventral midlines of the metasome.…”

Section: The Potential Of Molecular Genetic Data For Providing Insighmentioning

confidence: 99%

“…A mat of axons spreads out along the basement membrane, which is thickened in certain areas of the ectoderm, at the base of the proboscis, along the anterodorsal region of the body in the mesosome and in both the dorsal and ventral midlines of the metasome. In the proboscis ectoderm, there is a dense concentration of nerve cells that have been proposed to be primarily sensory (Bullock 1945;Knight-Jones 1952) and is particularly thick at the base of the proboscis (Brambell & Cole 1939).…”

Section: The Potential Of Molecular Genetic Data For Providing Insighmentioning

confidence: 99%

“…The cell bodies project their axons across the midline and continue posteriorly within the collar cord. It is not known where the axons finally project; Bullock (1945) proposed that they innervate the ventrolateral muscles of the trunk and suspected that their primary function is to elicit a rapid contraction of these muscles. However, several groups do not possess giant axons and yet are still able to elicit a rapid retreat, so the role of the giant axons remains uncertain (Pickens 1973).…”

Section: The Potential Of Molecular Genetic Data For Providing Insighmentioning

confidence: 99%

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Molecular genetic insights into deuterostome evolution from the direct-developing hemichordateSaccoglossus kowalevskii

Lowe

2008

Phil. Trans. R. Soc. B

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Progress in developmental biology, phylogenomics and palaeontology over the past five years are all making major contributions to a long-enduring problem in comparative biology: the early origins of the deuterostome phyla. Recent advances in the developmental biology of hemichordates have given a unique insight into developmental similarities between this phylum and chordates. Transcriptional and signalling gene expression patterns between the two groups during the early development of the anteroposterior and dorsoventral axes reveal close similarities, despite large morphological disparity between the body plans. These genetic networks have been proposed to play conserved roles in patterning centralized nervous systems in metazoans, yet seem to play a conserved role in patterning the diffusely organized basiepithelial nerve net of the hemichordates. Developmental genetic data are providing a unique insight into early deuterostome evolution, revealing a complexity of genetic regulation previously attributed only to vertebrates. While these data allow for key insights into the development of early deuterostomes, their utility for reconstructing ancestral morphologies is less certain, and morphological, palaeontological and molecular datasets should all be considered carefully when speculating about ancestral deuterostome features.

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Section: Anteroposterior Patterning In Hemichordatesmentioning

confidence: 61%

Section: Problems Reconstructing Ancestral Deuterostome Charactersmentioning

confidence: 99%

Section: The Potential Of Molecular Genetic Data For Providing Insighmentioning

confidence: 99%

Section: The Potential Of Molecular Genetic Data For Providing Insighmentioning

confidence: 99%

Section: The Potential Of Molecular Genetic Data For Providing Insighmentioning

confidence: 99%

See 3 more Smart Citations

Molecular genetic insights into deuterostome evolution from the direct-developing hemichordateSaccoglossus kowalevskii

Lowe

2008

Phil. Trans. R. Soc. B

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A Contribution from the Study of Cords of Lower Forms

Bullock¹

1953

Ciba Foundation Symposium ‐ the Spinal Cord

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Neural anatomy of echinoid early juveniles and comparison of nervous system organization in echinoderms

Formery

Orange

Formery³

et al. 2020

J of Comparative Neurology

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The echinoderms are a phylum of marine deuterostomes characterized by the pentaradial (five fold) symmetry of their adult bodies. Due to this unusual body plan, adult echinoderms have long been excluded from comparative analyses aimed at understanding the origin and evolution of deuterostome nervous systems. Here, we investigated the neural anatomy of early juveniles of representatives of three of the five echinoderm classes: the echinoid Paracentrotus lividus, the asteroid Patiria miniata, and the holothuroid Parastichopus parvimensis. Using whole mount immunohistochemistry and confocal microscopy, we found that the nervous system of echinoid early juveniles is composed of three main structures: a basiepidermal nerve plexus, five radial nerve cords connected by a circumoral nerve ring, and peripheral nerves innervating the appendages. Our whole mount preparations further allowed us to obtain thorough descriptions of these structures and of several innervation patterns, in particular at the level of the appendages. Detailed comparisons of the echinoid juvenile nervous system with those of asteroid and holothuroid juveniles moreover supported a general conservation of the main neural structures in all three species, including at the level of the appendages. Our results support the previously proposed hypotheses for the existence of two neural units in echinoderms: one consisting of the basiepidermal nerve plexus to process sensory stimuli locally and one composed of the radial nerve cords and the peripheral nerves constituting a centralized control system. This study provides the basis for more in‐depth comparisons of the echinoderm adult nervous system with those of other animals, in particular hemichordates and chordates, to address the long‐standing controversies about deuterostome nervous system evolution.

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The Functional Organization of the Nervous System of Enteropneusta

Cited by 61 publications

References 15 publications

Molecular genetic insights into deuterostome evolution from the direct-developing hemichordateSaccoglossus kowalevskii

Molecular genetic insights into deuterostome evolution from the direct-developing hemichordateSaccoglossus kowalevskii

A Contribution from the Study of Cords of Lower Forms

Neural anatomy of echinoid early juveniles and comparison of nervous system organization in echinoderms

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