Development of <i>Montipora hispida</i>.

<p>(A) Egg-sperm bundle; <i>Symbiodinium</i> (darker spots within the eggs) are distributed throughout the eggs. (B) Section of egg-sperm bundle, showing sperm (s) tightly packed in the middle of the bundle, surrounded by eggs (e). (C) Polar bodies (pb) on the surface of the egg. (D) Enlargement of <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0084115#pone-0084115-g003" target="_blank">Figure 3C</a>; (E) Section of egg. <i>Symbiodinium</i> are marked with arrowheads in this and succeeding panels. (F) The first cleavage results in a heart-shaped embryo. (G) Four-cell stage; the nucleus occupies a substantial part of each cell. (H) Embryos at the 4-16 cell stage, showing unevenly dispersed <i>Symbiodinium</i> in the arrowed embryos. (I) The 32-64 cell stage; again with <i>Symbiodinium</i> unevenly dispersed near the surface of the embryo. (J) Section of an embryo comparable to I. (K) Section of slightly older embryo. (L) Section of prawn chip stage. (M) Bowl-shaped stage, viewed from above. (N) Section of stage comparable to M, the embryo has become thicker. (O) Spherical stage, the asterisk in this and the following panels indicates the blastopore. (P) Section of an embryo similar to that shown in O. At this stage the mesoglea is gradually forming and <i>Symbiodinium</i> are moving into the endoderm. (Q) Later spherical stage; the mesoglea has clearly formed, with a row of ectodermal nuclei just above it (arrow). Few <i>Symbiodinium</i> are now seen in the ectoderm. (R) Pear-shaped planula stage. (S) Section of embryo comparable to that shown in R. There is a line of nuclei located in the columnar ectodermal cells, just above the mesoglea (arrows). (T) Section of elongated planula; the ectodermal cells are variously differentiated and the pharynx has grown inward.