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Light perception in brittle stars: detection of the molecular actors

Jerome Delroisse1*, Jérôme Mallefet2 and Patrick Flammang1
  • 1 University of Mons, Marine Biology Organisms & Biomimetics, Belgium
  • 2 University of Louvain-La-Neuve, Marine Biology, Belgium

Echinoderm photoreception is usually considered as enigmatic because of the lack of eyes in most of the species. Although a diffuse dermal and/or neural light sense has been described in some echinoderms (1), in sea urchins and sea stars photoreceptor cells expressing opsins are localized in specialized organs: the tube feet and the optic cushions on the arm tip, respectively (2,3,4). However, opsins are also expressed in the aboral integument of sea urchins and sea stars, indicating that light perception is certainly a multi-component process (5). Numerous brittle stars are described as light sensitive (6) though almost nothing is known about photoreception in the class Ophiuroidea. Lens-like arm plates were identified in Ophiocoma wendtii and, together with the underlying photoreceptors, could constitute a new type of compound eye (7,8). In the European brittle star Amphiura filiformis, light perception is unequivocal and allows the animal to adapt its feeding activity to the day/night cycle (9,10). This species could also use photoreceptors to perceive its own bioluminescence. Light perception at the level of bioluminescent organs has already been described for a cephalopod (11) and a ctenophore (12) and could also occur in brittle stars. Transcriptome profiling in A. filiformis indicate the expression of both opsins and cryptochrome. If cryptochromes are considered as components of the circadian clock that control daily rhythms (13), opsins are the main actors of vision in metazoans (14). A. filiformis is characterized by the expression of two opsin mRNAs, which were mainly detected in regenerating arms. Phylogenetic analysis revealed one Go-opsin and one R-opsin. The retinol metabolism pathway needed for the synthesis of the opsin light sensitive chromophore was also retrieved in the transcriptome. Finally, several drosophila-like and mammalian-like phototransduction actors were identified in arm tissues, confirming the implication of an opsin-based system. These opsins are probably involved in ambient light perception and also, possibly, in bioluminescence perception. A cryptochrome-mediated process could secondarily complete the role of the opsins or at least be linked to the day/night rhythm perception.

References

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Keywords: echinoderm, ophiuroid, photoreception, Opsin, Cryptochrome

Conference: International Conference on Invertebrate Vision, Fjälkinge, Sweden, 1 Aug - 8 Aug, 2013.

Presentation Type: Poster presentation preferred

Topic: Development and evolution

Citation: Delroisse J, Mallefet J and Flammang P (2019). Light perception in brittle stars: detection of the molecular actors. Front. Physiol. Conference Abstract: International Conference on Invertebrate Vision. doi: 10.3389/conf.fphys.2013.25.00037

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Received: 07 May 2013; Published Online: 09 Dec 2019.

* Correspondence: Mr. Jerome Delroisse, University of Mons, Marine Biology Organisms & Biomimetics, Mons, Hainaut, 7000, Belgium, jerome.delroisse@umons.ac.be