The cornucopia of copepod eyes: the evolution of extreme visual system novelty
Steck, M.; Theam, K.C.; Porter, M.L. (2023). The cornucopia of copepod eyes: the evolution of extreme visual system novelty, in: Buschbeck, E. et al. Distributed vision. From simple sensors to sophisticated combination eyes. pp. 223-266. https://dx.doi.org/10.1007/978-3-031-23216-9_9
In: Buschbeck, E.; Bok, M. (Ed.) (2023). Distributed vision. From simple sensors to sophisticated combination eyes. Springer: Cham. ISBN 978-3-031-23215-2; e-ISBN 978-3-031-23216-9. vii, 320 pp. https://dx.doi.org/10.1007/978-3-031-23216-9, more
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| Author keywords |
Copepoda; naupliar eye; lens diversity; Gicklhorn’s organ |
| Authors | | Top |
- Steck, M.
- Theam, K.C.
- Porter, M.L.
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| Abstract |
Copepods are a miniscule but ecologically significant group of organisms that thrive in a multitude of aquatic habitats. Despite being toe-high to a grasshopper, multiple visually mediated behaviors exist that would suggest that vision is an important sensory mode to this subclass of crustaceans. Unlike many other crustacean lineages, adult copepods have tripartite naupliar eyes that in the most typical form have three fused ocellar cups, each made up of three parts: a retinal sphere, a tapetal layer, and a surrounding pigment cup. The form and function of naupliar eyes have not been well cataloged across the copepods, but the species studied thus far display an inordinate amount of diversification. Across species, modifications to the ocellar components of the typical naupliar eye structure can range from complete loss to extreme enlargement, separation of the cups into three independent eyes, and the addition of an astonishingly diverse array of focusing structures, including multiple crystalline or cuticular lenses. Modifications to the typical copepod naupliar eye structure have been histologically identified in four of the ten currently described copepod orders; additional eye diversity is likely to exist among the remaining unstudied groups as well. In this review, we assemble all of the currently available data on copepod naupliar eye function and structure to highlight the extreme diversity of visual modifications in the group, underscore how much is still unknown, reinvigorate research of copepod eyes, and provide a comprehensive evolutionary framework for future studies. Although the eyes of many species are not yet fully characterized, the visual modifications described here indicate that despite their minute size, copepods are often highly visual creatures with eyes that are an evolutionary playground of diversity. |
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