Ophiocoma wendtii
Ophiocoma wendtii is a species of brittle stars that inhabits coral reefs from Bermuda to Brazil. It is known for its advanced compound eyes. These brittle stars have long, thin arms emanating from a small, disk-shaped body, and are about the size of an outstretched human hand.[1]
| Ophiocoma wendtii | |
|---|---|
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Echinodermata |
| Class: | Ophiuroidea |
| Order: | Ophiacanthida |
| Family: | Ophiocomidae |
| Genus: | Ophiocoma |
| Species: | O. wendtii |
| Binomial name | |
| Ophiocoma wendtii | |
Visual system
Its arms are covered with calcite crystals. In addition to functioning as an armor and giving structural support, the crystals were, until recently, thought to form a visual system. They minimize spherical aberration of incoming light and have excellent optical properties. The lenses were suggested to work by filtering and focusing light on an underlying photoreceptor system. Nerve bundles under each lens, presumed to be light-sensitive, would transmit the optical information to the rest of the nervous system.[1] However, the discovery of nerves and photoreceptor cells in between, rather than beneath, the lenses suggests that this system may not rely on their optical properties.[2]
The only known animals to employ a similar visual system were the now-extinct trilobites. Phototropic chromatophores can change O. wendtii's color and regulate how much light will reach the photoreceptors.[3]
References
- John Roach (22 August 2001). "Brittle Star Found Covered With Optically Advanced "Eyes"". National Geographic News. Archived from the original on 3 October 2001.
- Sumner-Rooney, Lauren; Rahman, Imran A.; Sigwart, Julia D.; Ullrich-Lüter, Esther (2018). "Whole-body photoreceptor networks are independent of 'lenses' in brittle stars". Proceedings of the Royal Society B: Biological Sciences. 285 (1871): 20172590. doi:10.1098/rspb.2017.2590. PMC 5805950. PMID 29367398.
- Sumner-Rooney, Lauren; Kirwan, John D.; Lowe, Elijah; Ullrich-Lüter, Esther (2020). "Extraocular vision in a brittle star is mediated by chromatophore movement in response to ambient light". Current Biology. doi:10.1016/j.cub.2019.11.042.
Further reading
- Vukusic, Pete; Sambles, J. Roy (2003). "Photonic structures in biology". Nature. 424 (6950): 852–855. Bibcode:2003Natur.424..852V. doi:10.1038/nature01941. PMID 12917700.