A simple visual system without neurons in jellyfish larvae

Karin Nordström, Rita Wallén, Jamie Seymour, Dan Nilsson

Research output: Contribution to journalArticlepeer-review

96 Citations (Scopus)


Earlier detailed studies of cnidarian planula larvae have revealed a simple nervous system but no eyes or identifiable light sensing structures. Here, we describe the planula of a box jellyfish, Tripedalia cystophora, and report that these larvae have an extremely simple organization with no nervous system at all. Their only advanced feature is the presence of 10-15 pigment-cup ocelli, evenly spaced across the posterior half of the larval ectoderm. The ocelli are single cell structures containing a cup of screening pigment filled with presumably photosensory microvilli. These rhabdomeric photoreceptors have no neural connections to any other cells, but each has a well-developed motor-cilium, appearing to be the only means by which light can control the behaviour of the larva. The ocelli are thus self-contained sensory-motor entities, making a nervous system superfluous.

Original languageEnglish
Pages (from-to)2349-2354
Number of pages6
JournalProceedings of the Royal Society B: Biological Sciences
Issue number1531
Publication statusPublished - 22 Nov 2003
Externally publishedYes


  • Chironex fleckerii
  • Chiropsalmus sp.
  • Pigment-cup ocelli
  • Planula
  • Rhabdomeric photoreceptor
  • Tripedalia cystophora


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