Abstract
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.
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Selected References
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- Arendt Detlev, Tessmar Kristin, de Campos-Baptista Maria-Ines Medeiros, Dorresteijn Adriaan, Wittbrodt Joachim. Development of pigment-cup eyes in the polychaete Platynereis dumerilii and evolutionary conservation of larval eyes in Bilateria. Development. 2002 Mar;129(5):1143–1154. doi: 10.1242/dev.129.5.1143. [DOI] [PubMed] [Google Scholar]
- Eakin R. M., Brandenberger J. L. Unique eye of probable evolutionary significance. Science. 1981 Mar 13;211(4487):1189–1190. doi: 10.1126/science.7466394. [DOI] [PubMed] [Google Scholar]
- Fernald R. D. Evolution of eyes. Curr Opin Neurobiol. 2000 Aug;10(4):444–450. doi: 10.1016/s0959-4388(00)00114-8. [DOI] [PubMed] [Google Scholar]
- Gröger H., Schmid V. Larval development in Cnidaria: a connection to Bilateria? Genesis. 2001 Mar;29(3):110–114. doi: 10.1002/gene.1013. [DOI] [PubMed] [Google Scholar]
- Hayward D. C., Catmull J., Reece-Hoyes J. S., Berghammer H., Dodd H., Hann S. J., Miller D. J., Ball E. E. Gene structure and larval expression of cnox-2Am from the coral Acropora millepora. Dev Genes Evol. 2001 Jan;211(1):10–19. doi: 10.1007/s004270000112. [DOI] [PubMed] [Google Scholar]
- Hayward David C., Samuel Gabrielle, Pontynen Patricia C., Catmull Julian, Saint Robert, Miller David J., Ball Eldon E. Localized expression of a dpp/BMP2/4 ortholog in a coral embryo. Proc Natl Acad Sci U S A. 2002 Jun 4;99(12):8106–8111. doi: 10.1073/pnas.112021499. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Nilsson D. E. Eye ancestry: old genes for new eyes. Curr Biol. 1996 Jan 1;6(1):39–42. doi: 10.1016/s0960-9822(02)00417-7. [DOI] [PubMed] [Google Scholar]
- Okada T., Higuchi M., Takano M., Maruyama T., Imai Y., Osawa T. Anti-tumour efficacy of mouse spleen cells separated with Dolichos biflorus lectin (DBA) in experimental pulmonary metastasis of B16 melanoma cells. Br J Cancer. 1990 Feb;61(2):241–249. doi: 10.1038/bjc.1990.45. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Pearse J. S., Pearse V. B. Vision of cubomedusan jellyfishes. Science. 1978 Jan 27;199(4327):458–458. doi: 10.1126/science.22934. [DOI] [PubMed] [Google Scholar]
- Singla C. L. Ocelli of hydromedusae. Cell Tissue Res. 1974 Jun 12;149(3):413–429. doi: 10.1007/BF00226774. [DOI] [PubMed] [Google Scholar]