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Spectral sensitivity in Onychophora (velvet worms) revealed by electroretinograms, phototactic behaviour and opsin gene expression.

Beckmann, Holger; Hering, Lars; Henze, Miriam LU ; Kelber, Almut LU ; Stevenson, Paul A and Mayer, Georg (2015) In Journal of Experimental Biology 218(6). p.915-922
Abstract
Onychophorans typically possess a pair of simple eyes, inherited from the last common ancestor of Panarthropoda (Onychophora + Tardigrada + Arthropoda). These visual organs are thought to be homologous to the arthropod median ocelli, whereas the compound eyes most likely evolved in the arthropod lineage. To gain insights into the ancestral function and evolution of the visual system in panarthropods, we investigated phototactic behaviour, opsin gene expression and the spectral sensitivity of the eyes in two representative species of Onychophora: Euperipatoides rowelli (Peripatopsidae), and Principapillatus hitoyensis (Peripatidae). Our behavioural analyses, in conjunction with previous data, demonstrate that both species exhibit... (More)
Onychophorans typically possess a pair of simple eyes, inherited from the last common ancestor of Panarthropoda (Onychophora + Tardigrada + Arthropoda). These visual organs are thought to be homologous to the arthropod median ocelli, whereas the compound eyes most likely evolved in the arthropod lineage. To gain insights into the ancestral function and evolution of the visual system in panarthropods, we investigated phototactic behaviour, opsin gene expression and the spectral sensitivity of the eyes in two representative species of Onychophora: Euperipatoides rowelli (Peripatopsidae), and Principapillatus hitoyensis (Peripatidae). Our behavioural analyses, in conjunction with previous data, demonstrate that both species exhibit photonegative responses to wavelengths ranging from ultraviolet to green light (370-530 nm), while electroretinograms reveal that the onychophoran eye is maximally sensitive to blue light (peak sensitivity ~480 nm). Template fits to the obtained sensitivities suggest that the onychophoran eye is monochromatic. To clarify on which type of opsin the single visual pigment is based, we localised the corresponding mRNA in the onychophoran eye and brain using in situ hybridization. Our data show that the r-opsin gene (onychopsin) is expressed exclusively in the photoreceptor cells of the eye, whereas the c-opsin mRNA is confined to optic ganglion cells and the brain. Together, our findings suggest that the onychopsin is involved in vision, whereas the c-opsin might have a photoreceptive, non-visual function in onychophorans. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of Experimental Biology
volume
218
issue
6
pages
915 - 922
publisher
The Company of Biologists Ltd
external identifiers
  • pmid:25617459
  • wos:000351397500017
  • scopus:84926034775
ISSN
1477-9145
DOI
10.1242/jeb.116780
language
English
LU publication?
yes
id
e73bbd94-1dd5-452d-803d-3294e4a0741d (old id 5039824)
date added to LUP
2015-02-26 13:36:55
date last changed
2017-11-19 03:00:35
@article{e73bbd94-1dd5-452d-803d-3294e4a0741d,
  abstract     = {Onychophorans typically possess a pair of simple eyes, inherited from the last common ancestor of Panarthropoda (Onychophora + Tardigrada + Arthropoda). These visual organs are thought to be homologous to the arthropod median ocelli, whereas the compound eyes most likely evolved in the arthropod lineage. To gain insights into the ancestral function and evolution of the visual system in panarthropods, we investigated phototactic behaviour, opsin gene expression and the spectral sensitivity of the eyes in two representative species of Onychophora: Euperipatoides rowelli (Peripatopsidae), and Principapillatus hitoyensis (Peripatidae). Our behavioural analyses, in conjunction with previous data, demonstrate that both species exhibit photonegative responses to wavelengths ranging from ultraviolet to green light (370-530 nm), while electroretinograms reveal that the onychophoran eye is maximally sensitive to blue light (peak sensitivity ~480 nm). Template fits to the obtained sensitivities suggest that the onychophoran eye is monochromatic. To clarify on which type of opsin the single visual pigment is based, we localised the corresponding mRNA in the onychophoran eye and brain using in situ hybridization. Our data show that the r-opsin gene (onychopsin) is expressed exclusively in the photoreceptor cells of the eye, whereas the c-opsin mRNA is confined to optic ganglion cells and the brain. Together, our findings suggest that the onychopsin is involved in vision, whereas the c-opsin might have a photoreceptive, non-visual function in onychophorans.},
  author       = {Beckmann, Holger and Hering, Lars and Henze, Miriam and Kelber, Almut and Stevenson, Paul A and Mayer, Georg},
  issn         = {1477-9145},
  language     = {eng},
  number       = {6},
  pages        = {915--922},
  publisher    = {The Company of Biologists Ltd},
  series       = {Journal of Experimental Biology},
  title        = {Spectral sensitivity in Onychophora (velvet worms) revealed by electroretinograms, phototactic behaviour and opsin gene expression.},
  url          = {http://dx.doi.org/10.1242/jeb.116780},
  volume       = {218},
  year         = {2015},
}