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Figure 4 | Frontiers in Zoology

Figure 4

From: Development and juvenile anatomy of the nemertodermatid Meara stichopi (Bock) Westblad 1949 (Acoelomorpha)

Figure 4

Early cleavage pattern of Meara stichopi embryos. Nuclear labeling with Propidium Iodide (magenta), cell cortices and spindle with BODIPY FL-Phallacidin (green) Left row Maximum Intensity Projections, right row optical sections. A) 2-cell stage (3 days after fertilization). One of the polar bodies (pb) is visible at the animal pole. A’) shows an optical section through the same embryo. Propidium iodide is labeling the chromatin in the nucleus (nc) as well as the centrosomes (ct). Both blastomeres are equal in size. B) After 4.5 days, the 4-cell stage has large blastomeres at the vegetal pole, and two smaller daughter blastomeres at the animal pole. B’) shows a section of the embryo in B). The spindles are arranged for the future direction of cell division. C) After 5.5 days the 8-cell stage is composed out of four larger cells at the vegetal pole with four blastomeres at the animal pole. C’ shows an optical section of the embryo of C), with spindles arranged to the future plane of division. D) 16-cell stage reached 7 days after fertilization. The size differences between the blastomeres are less prominent and the arrangement is variable. D’) BODIPY FL-phallacidin labeled cell borders as well as the centrosomes, while the chromatin is labeled by propidium iodide. E) 24-cell stage after 8.5 days. E’) shows a median section of the embryo shown in E). The blastocoel is bordered with the phallacidin labeled cell cortex of the outer blastomeres. F) 64-cell stage 10.5 days after fertilization. F’ shows the cells that have been internalized (blastomeres labeled with arrowhead) during the transition from the 24 to the 64 cell stage. Sister blastomeres are connected by white bars, animal pole is indicated with an asterisk. Scale bar: 30 μm.

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