Corrections DEVELOPMENTAL BIOLOGY Correction for “The planarian Schmidtea mediterranea as a model for epigenetic germ cell specification: Analysis of ESTs from the hermaphroditic strain,” by

DEVELOPMENTAL BIOLOGY Correction for “The planarian Schmidtea mediterranea as a model for epigenetic germ cell specification: Analysis of ESTs from the hermaphroditic strain,” by Ricardo M. Zayas, Alvaro Hernández, Bianca Habermann, Yuying Wang, Joel M. Stary, and Phillip A. Newmark, which appeared in issue 51, December 20, 2005, of Proc Natl Acad Sci USA (102:18491–18496; first published December 12, 2005; 10.1073/pnas.0509507102). The authors note that on page 18496, left column, the first full paragraph appeared incorrectly. This paragraph should instead appear as the following: For in situ analysis, we also chose additional candidate genes implicated in reproductive processes based on BLASTX similarity; these genes were not annotated to the GO term “reproduction.” For example, we studied planarian homologues of cdc-5/polo-like kinases, important regulators of cell cycle checkpoints (54) also implicated in the coordination of chromosome segregation during meiosis (55); the mammalian sperm tail protein, Shippo-1 (56); and spermatid elongation defective 1 (sped-1), a gene required for proper spermatid elongation. All of these genes were expressed in the planarian testes. A planarian homologue of gld-1, a gene required for oocyte development in C. elegans (58), was detected in the ovaries and oviducts (Fig. 4A). The expression of sped-1-like mRNA was used to monitor the development of the testes (Fig. 4B). sped-1-like mRNA was not detected in 2to 3-day-old hatchlings; the transcript was first detectable in the testes primordia of juvenile planarians and strongly expressed in the testes of mature worms (Fig. 4B). sped-1-like mRNA was not detected in asexual worms; consistent with this observation, Northern blot analysis showed that this gene is expressed at high levels in sexual worms but is undetectable in asexual animals (data not shown). These results provide additional evidence that the planarian reproductive organs are formed postembryonically (5, 8–11, 14). In addition, Fig. 4 and its legend appeared incorrectly. The corrected figure and its legend appear below.