Structural and functional organization of the visual system in the microphthalmic cave beetle Ptomaphagus hirtus
-
1
Wayne State University, Department of Biological Sciences, United States
-
2
University of Cincinnati, Department of Biology, United States
Strongly cave adapted animal species are invariably characterized by strong eye reduction (microphthalmy) to the complete loss of eyes (anophthalmy). Recent studies of cave adaptation have focused on the causes and mechanisms underlying the regressive evolution of the visual system but little attention has been paid to aspects of vision, which can remain conserved in the low-light level ecologies of caves. The small carrion beetle genus Ptomaphagus (Staphyliniformia: Leiodidae) includes both surface-living as well as obligatory cave dwelling species (troglobionts), which range from mildly microphthalmic to anophthalmic. Combining findings from transcriptomic and behavioral analyses, we previously reported evidence that the troglobiotic representative Ptomaphagus hirtus of Mammoth cave, which lacks compound eyes, possesses a functional visual system that facilitates negative phototaxis (Friedrich et al. 2011 Journal of Experimental Biology 214: 3532-3541).
In recent experiments, we expanded our analysis of the P. hirtus visual system. In wavelength-specific light-dark choice tests applying similar light intensities (1E+15-1E+16 photons/cm2/s), adult P. hirtus exhibited no detectable photoresponse to red light or blue light but to green light, as predicted from the conservation and expression of a long wavelength-sensitive opsin in this species. However, P. hirtus reacted also photonegatively to UV-light in addition to green light, possibly reflecting an additional sensitivity peak of the identified long wavelength-sensitive opsin.
At the structural level, transmission electron microscopy identified a population of putative photoreceptors with loosely organized microvillar concentrations in the lens-eye like structure of the lateral P. hirtus head. The photoreceptor assembly is embedded in a lens-covered cuticle pocket and projects an optic nerve to a small optic neuropile. These features are consistent with comparative evidence that the candidate visual organs of P. hirtus represent conserved, highly compacted relicts of ancestral compound eyes. In ongoing studies, we are exploring the sensitivity of the P. hirtus visual system in comparison to surface species.
Keywords:
cave adaptation,
Compound eye,
regressive evolution,
Opsins,
phototaxis,
Photoreceptor Cells, Invertebrate
Conference:
International Conference on Invertebrate Vision, Fjälkinge, Sweden, 1 Aug - 8 Aug, 2013.
Presentation Type:
Oral presentation preferred
Topic:
Development and evolution
Citation:
Friedrich
M,
Kulacic
J and
Buschbeck
EK
(2019). Structural and functional organization of the visual system in the microphthalmic cave beetle Ptomaphagus hirtus.
Front. Physiol.
Conference Abstract:
International Conference on Invertebrate Vision.
doi: 10.3389/conf.fphys.2013.25.00019
Copyright:
The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers.
They are made available through the Frontiers publishing platform as a service to conference organizers and presenters.
The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated.
Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed.
For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions.
Received:
01 Mar 2013;
Published Online:
09 Dec 2019.
*
Correspondence:
Dr. Markus Friedrich, Wayne State University, Department of Biological Sciences, Detroit, United States, ag7274@wayne.edu