Rhopalium

Moon jelly (Aurelia aurita) with rhopalia visible in indentations of rim

Rhopalia (singular: rhopalium) are small sensory structures of Scyphozoa (typical jellyfish) and Cubozoa (box jellies). In Aurelia they lie in marginal indententions around the bell and are flanked by rhopalial lappets. Specialized structures to sense light (ocelli) and perceive gravity (statoliths) are usually present. They also control the pace of swimming-muscle contraction.

Cubozoan ocelli are the most complex of Cnidarians, and resemble the image-forming eyes of squids, octopuses and vertebrates.

swing of the rhopalia of Tripedalia cystophora

See also

• Nerve net

References

• Meglitsch, Paul A. (1991). Invertebrate Zoology, Oxford University Press, 86. ISBN 0-19-504900-4.
• Ruppert, Edward E.; and Fox, Richard S. (1988). Seashore Animals of the Southeast, University of South Carolina Press, 29. ISBN 0-87249-535-3.

External links

• The Jellyfish homepage - University of New South Wales
• The Tree of Life - Cnidaria

Vision in animals
Vision	Birds Cats Chameleons Dinosaurs Dogs Fishes Horses Toads
Eyes	Arthropod eye Compound eye Eagle eye Eye shine Simple eye in invertebrates Mammalian eye Human eye Mollusc eye Cephalopod eye Gastropod eye Holochroal eye Parietal eye Schizochroal eye
Evolution	Evolution of the eye Evolution of color vision Evolution of color vision in primates
Coloration	Albinism in biology Animal coloration Aposematism Camouflage Chromatophore Counter-illumination Countershading Crypsis Deimatic behaviour Disruptive coloration Eyespot (mimicry) Mimicry Structural coloration Underwater camouflage
Related topics	Animal senses Blindness in animals Eyespot apparatus Feature detection Infrared sensing in snakes Monocular deprivation Ommatidium Palpebral (bone) Pseudopupil Rhopalium Underwater vision Visual perception