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. Author manuscript; available in PMC: 2014 May 20.
Published in final edited form as: J Exp Zool B Mol Dev Evol. 2010 Dec 6;0(2):113–134. doi: 10.1002/jez.b.21383

Figure 1.

Figure 1

Prehatching development of A. californica. A. californica develops through unequal spiral cleavage inside a protective egg mass (A–E). The vegetal pole (VP) contains more yolk than the animal pole (AP), as can be seen in panel A. Polar bodies (Pb) are visible until approximately the third cleavage (C). Cells in the animal pole divide much faster than cells in the vegetal pole (C–E). Gastrulation occurs through epiboly (F–H). The segmentation cavity (Sc) is surrounded by the two macromeres (visible in panel C). In panel G, the mesoteloblast cells (Mb) and anal cells (Ac) are both visible. After gastrulation (F–H), a trochophore larva (I) is formed inside this egg mass. The trochophore stage has a ciliated prototroch (Pt) and apical tuft (At). Note that the telotroch is missing in the image. Subsequently, early rudiments of the veliger body plan (J–L) become visible, such as the foot (Ft) and the velar lobes (Vl). Before hatching from the egg mass, a complete veliger larva is formed (L). Scale bar sizes: A: 20 μm; B: 21 μm; C: 18 μm; D: 20 μm; E: 20 μm; F: 35 μm; G: 25 μm; H: 22 μm; I: 41 μm; J: 32 μm; K: 26 μm; L: 35 μm. Legend: Ac, anal cells; AP, animal pole; At, apical tuft; Ft, foot; Ma, mantle region; Mb, mesoteloblast cells; Op, operculum; Pb, polar bodies; Pt, prototroch; Sc, segmentation cavity; Vl, velar lobe; VP, vegetal pole.