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The visual system of harvestmen (Opiliones, Arachnida, Chelicerata) – a re-examination

BACKGROUND: The visual systems in chelicerates are poorly understood, even though they show strong variation in eye and visual neuropil architecture, thus may provide valuable insights for the understanding of chelicerate phylogeny and eye evolution. Comparable morphological characters are desperate...

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Autores principales: Lehmann, Tobias, Lodde-Bensch, Eva, Melzer, Roland R., Metz, Martina
Formato: Online Artículo Texto
Lenguaje:English
Publicado: BioMed Central 2016
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5112708/
https://www.ncbi.nlm.nih.gov/pubmed/27891163
http://dx.doi.org/10.1186/s12983-016-0182-9
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author Lehmann, Tobias
Lodde-Bensch, Eva
Melzer, Roland R.
Metz, Martina
author_facet Lehmann, Tobias
Lodde-Bensch, Eva
Melzer, Roland R.
Metz, Martina
author_sort Lehmann, Tobias
collection PubMed
description BACKGROUND: The visual systems in chelicerates are poorly understood, even though they show strong variation in eye and visual neuropil architecture, thus may provide valuable insights for the understanding of chelicerate phylogeny and eye evolution. Comparable morphological characters are desperately sought for reconstructions of the phylogeny of Chelicerata, especially with respect to Arachnida. So far, reliable data exist only for Pycnogonida, Xiphosura, Scorpiones, and Araneae. The few earlier studies of the organisation of the visual system in harvestmen are contradictory concerning the number, morphology, and position of the visual neuropils. RESULTS: We undertook a descriptive and comparative analysis of the neuroanatomy of the visual system in several phalangid harvestmen species. Various traditional and modern methods were used that allow comparisons with previous results (cobalt fills, DiI/DiO labelling, osmium ethyl gallate procedure, and TEM). The R-cells (photoreceptor and arhabdomeric cells) in the eyes of Opiliones are linked to a first and a second visual neuropil. The first visual neuropil receives input from all R-cell axons, in the second only few R-cells terminate in the distal part. Hence, the second visual neuropil is subdivided in a part with direct R-cell input and a part without. The arcuate body is located in a subsequent position with direct contact to the second visual neuropil. CONCLUSIONS: This re-examination comes to conclusions different from those of all previous studies. The visual system of phalangid Opiliones occupies an intermediate position between Pycnogonida, Xiphosura, and Scorpiones on the one side, and Araneae on the other side. The projection of the R-cells is similar to that in the former grouping, the general neuropil arrangement to that in the latter taxon. However, more research on the visual systems in other chelicerate orders is needed in order to draw inferences on phylogeny or eye evolution.
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spelling pubmed-51127082016-11-25 The visual system of harvestmen (Opiliones, Arachnida, Chelicerata) – a re-examination Lehmann, Tobias Lodde-Bensch, Eva Melzer, Roland R. Metz, Martina Front Zool Research BACKGROUND: The visual systems in chelicerates are poorly understood, even though they show strong variation in eye and visual neuropil architecture, thus may provide valuable insights for the understanding of chelicerate phylogeny and eye evolution. Comparable morphological characters are desperately sought for reconstructions of the phylogeny of Chelicerata, especially with respect to Arachnida. So far, reliable data exist only for Pycnogonida, Xiphosura, Scorpiones, and Araneae. The few earlier studies of the organisation of the visual system in harvestmen are contradictory concerning the number, morphology, and position of the visual neuropils. RESULTS: We undertook a descriptive and comparative analysis of the neuroanatomy of the visual system in several phalangid harvestmen species. Various traditional and modern methods were used that allow comparisons with previous results (cobalt fills, DiI/DiO labelling, osmium ethyl gallate procedure, and TEM). The R-cells (photoreceptor and arhabdomeric cells) in the eyes of Opiliones are linked to a first and a second visual neuropil. The first visual neuropil receives input from all R-cell axons, in the second only few R-cells terminate in the distal part. Hence, the second visual neuropil is subdivided in a part with direct R-cell input and a part without. The arcuate body is located in a subsequent position with direct contact to the second visual neuropil. CONCLUSIONS: This re-examination comes to conclusions different from those of all previous studies. The visual system of phalangid Opiliones occupies an intermediate position between Pycnogonida, Xiphosura, and Scorpiones on the one side, and Araneae on the other side. The projection of the R-cells is similar to that in the former grouping, the general neuropil arrangement to that in the latter taxon. However, more research on the visual systems in other chelicerate orders is needed in order to draw inferences on phylogeny or eye evolution. BioMed Central 2016-11-16 /pmc/articles/PMC5112708/ /pubmed/27891163 http://dx.doi.org/10.1186/s12983-016-0182-9 Text en © The Author(s). 2016 Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
spellingShingle Research
Lehmann, Tobias
Lodde-Bensch, Eva
Melzer, Roland R.
Metz, Martina
The visual system of harvestmen (Opiliones, Arachnida, Chelicerata) – a re-examination
title The visual system of harvestmen (Opiliones, Arachnida, Chelicerata) – a re-examination
title_full The visual system of harvestmen (Opiliones, Arachnida, Chelicerata) – a re-examination
title_fullStr The visual system of harvestmen (Opiliones, Arachnida, Chelicerata) – a re-examination
title_full_unstemmed The visual system of harvestmen (Opiliones, Arachnida, Chelicerata) – a re-examination
title_short The visual system of harvestmen (Opiliones, Arachnida, Chelicerata) – a re-examination
title_sort visual system of harvestmen (opiliones, arachnida, chelicerata) – a re-examination
topic Research
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5112708/
https://www.ncbi.nlm.nih.gov/pubmed/27891163
http://dx.doi.org/10.1186/s12983-016-0182-9
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