In:
eLife, eLife Sciences Publications, Ltd, Vol. 7 ( 2018-05-29)
Abstract:
The animal kingdom contains many different types of eyes, but all share certain features in common. All detect light using specialized cells called photoreceptors, of which there are two main kinds: ciliary and rhabdomeric. Crustaceans and their relatives, including insects, have rhabdomeric photoreceptors; while animals with backbones, including humans, have ciliary photoreceptors. There are also several groups of animals, mostly sea-dwellers, that inherited both types of photoreceptors from their ancestors that lived millions of years ago. These include the marine ragworm, Platynereis dumerilii. The larvae of Platynereis are free-swimming plankton. Each has a transparent brain and six small, pigmented eyes. The eyes contain rhabdomeric photoreceptors. These enable the larvae to detect and swim towards light sources. Yet the larval brain also contains ciliary photoreceptors, the role of which was unknown. Verasztó, Gühmann et al. now show that ultraviolet light activates ciliary photoreceptors, whereas cyan, or blue-green, light inhibits them. Shining ultraviolet light onto Platynereis larvae makes the larvae swim downwards. By contrast, cyan light makes the larvae swim upwards. In the ocean, ultraviolet light is most intense near the surface, while cyan light reaches greater depths. Ciliary photoreceptors thus help Platynereis to avoid harmful ultraviolet radiation near the surface. Though if the larvae swim too deep, cyan light inhibits the ciliary photoreceptors and activates the rhabdomeric pigmented eyes. This makes the larvae swim upwards again. Using high-powered microscopy, Verasztó, Gühmann et al. confirm that neural circuits containing ciliary photoreceptors exchange messages with circuits containing rhabdomeric photoreceptors. This suggests that the two work together to form a depth gauge. By enabling the larvae to swim at a preferred depth, the depth gauge influences where the worms end up as adults. Its discovery should also stimulate new ideas about the evolution of eyes and photoreceptors.
Type of Medium:
Online Resource
ISSN:
2050-084X
DOI:
10.7554/eLife.36440.001
DOI:
10.7554/eLife.36440.002
DOI:
10.7554/eLife.36440.003
DOI:
10.7554/eLife.36440.006
DOI:
10.7554/eLife.36440.007
DOI:
10.7554/eLife.36440.004
DOI:
10.7554/eLife.36440.005
DOI:
10.7554/eLife.36440.008
DOI:
10.7554/eLife.36440.009
DOI:
10.7554/eLife.36440.014
DOI:
10.7554/eLife.36440.010
DOI:
10.7554/eLife.36440.011
DOI:
10.7554/eLife.36440.012
DOI:
10.7554/eLife.36440.013
DOI:
10.7554/eLife.36440.015
DOI:
10.7554/eLife.36440.016
DOI:
10.7554/eLife.36440.017
DOI:
10.7554/eLife.36440.018
DOI:
10.7554/eLife.36440.019
DOI:
10.7554/eLife.36440.020
DOI:
10.7554/eLife.36440.021
DOI:
10.7554/eLife.36440.023
DOI:
10.7554/eLife.36440.024
Language:
English
Publisher:
eLife Sciences Publications, Ltd
Publication Date:
2018
detail.hit.zdb_id:
2687154-3
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