Figure 4.

Ipiwi1 expression (A-E) and Ipiwi1 protein (F-J) during postembryonic development of I. pulchra. In freshly hatched animals, a subset of somatic neoblasts was visible as small piwi expressing cells (arrowheads) beside six to eight larger strongly stained primordial germ cells (that also express nanos, see text) (arrows in A, B, F). Until day seven neoblast number increased, PGCs multiplied and gave rise to testes and ovaries. At day seven testes and developing eggs could be observed (C, H). At days 10 and 12, a chain of developing eggs was present medially and testes were present along the lateral margin (D, E, I, J). Note the accumulation of ipiwi1 in the genital blastema (open arrowhead in E, J) which gives rise to the genital organs. A similar genital blastema was observed during regeneration (see Figure. 4). In all pictures, anterior is to the left. t, testes; de, developing eggs; (asterisk) autofluorescence of digested diatoms in the central syncytium. Scale bars 100 μm.