Morphological and molecular development of the eyes during embryogenesis of the freshwater planarian Schmidtea polychroa
- 446 Downloads
Photoreception is one of the most primitive sensory functions in metazoans. Despite the diversity of forms and components of metazoan eyes, many studies have demonstrated the existence of a common cellular and molecular basis for their development. Genes like pax6, sine oculis, eyes absent, dachshund, otx, Rx and atonal are known to be associated with the specification and development of the eyes. In planarians, sine oculis, eyes absent and otxA play an essential role during the formation of the eye after decapitation, whereas pax6, considered by many authors as a master control gene for eye formation, does not seem to be involved in adult eye regeneration. Whether this is a peculiarity of adult planarians or, on the contrary, is also found in embryogenesis remains unknown. Herein, we characterize embryonic eye development in the planarian species Schmidtea polychroa using histological sections and molecular markers. Additionally, we analyse the expression pattern of the pax6–sine oculis–eyes absent–dachshund network, and the genes Rx, otxA, otxB and atonal. We demonstrate that eye formation in planarian embryos shows great similarities to adult eye regeneration, both at the cellular and molecular level. We thus conclude that planarian eyes exhibit divergent molecular patterning mechanisms compared to the prototypic ancestral metazoan eye.
KeywordsPlanarian Embryogenesis Eye pax6
We thank M. Vila-Farré and F. Cebrià for support and comments on this manuscript. JMM-D was an FPU fellow funded by the MICINN (Ministerio de Ciencia e Innovación), Spain. FM is an APIF fellow at the University of Barcelona, Spain. This work was supported by MEC BFU- 2007–63209, Spain, to RR.
- Frohman MA (1994) On beyond classic race (rapid amplification of cDNA ends). PCR Meth Appl 4:40–58Google Scholar
- Hyman LH (1951) The invertebrates, vol II. Platyhelminthes and Rhynchocoela. McGraw-Hill, New York, chap The PlatyhelminthesGoogle Scholar
- Le Moigne A (1963) Etude du développement embryonnaire de Polycelis nigra (Turbellarié, Triclade). Bull Soc Zool Fr 88:403–422Google Scholar
- Pineda D, González J, Marsal M, Saló E (2001) Evolutionary conservation of the initial eye genetic pathway in planarians. Belg J Zool 131(Supplement 1):77–82Google Scholar
- Rossi L, Batistoni R, Salvetti A, Deri P, Bernini F, Andreoli I, Falleni A, Gremigni V (2001) Molecular aspects of cell proliferation and neurogenesis in planarians. Belg J Zool 131(Supplement 1):83–87Google Scholar
- Salvini-Plawen L, Mayr E (1961) Evolutionary biology, vol 10. Plenum Press, New York, pp 207–263Google Scholar
- Sluys R (1989) A monograph of the marine triclads. Rotterdam & Brookfield, RotterdamGoogle Scholar
- Stevens NM (1904) On the germ cells and the embryology of Planaria simplicissima. Proc Acad Nat Sci Philadelphia 56:208–220Google Scholar