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Dev Genes Evol. 2006 Nov;216(11):667-81. Epub 2006 Aug 24.

Early embryogenesis of planaria: a cryptic larva feeding on maternal resources.

Author information

1
Molecular Cell and Developmental Biology, University of California Los Angeles, 621 Charles E. Young Drive South, Los Angeles, CA, 90095, USA. cardona@ucla.edu

Abstract

The early planarian embryo presents a complete ciliated epidermis and a pharynx and feeds on maternal yolk cells. In this paper, we report on all the elements involved in the formation of such an autonomous embryo, which we name cryptic larva. First, we provide a description of the spherical and fusiform yolk cells and their relationship with the blastomeres, from the laying of the egg capsule up to their final fate in mid embryonic stages. Then, we describe the early cleavage and the subsequent development of the tissues of the cryptic larva, namely, the primary epidermis, the embryonic pharynx, and a new cell type, the star cells. Finally, we discuss the possibility that the cryptic larva either constitutes a vestigial larva or, more likely, is the evolutionary result of the competition between multiple embryos for the limited and shared maternal resources in the egg capsule.

PMID:
16932928
DOI:
10.1007/s00427-006-0094-3
[Indexed for MEDLINE]

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