8.Some questions about the small micromeres. a. Early on in development, the mos

Question

8.Some questions about the small micromeres. a. Early on in development, the most vegetal cells, the micromeres, divide asymmetrically, leaving 4 large and 4 small micromeres. The small micromeres divide once more, leaving 8 small micromeres, which don't do any more dividing until the larva approaches metamorphosis. Do they remain the smallest cells in the developing organism? Why or why not? b. When the small micromeres do begin dividing again, where are they, and what adult structures or cell lines to they give rise to? c. Some descendents of the small micromeres don't make it through metamorphosis. Where are they and what happens to them?

Explanation / Answer

A. No. Until the development of the organism, these micromeres divide further to form a group of cells beneath the large tier. This is because they are a result of unequal division in the vegetal tier. This unequal division produces 4 macromeres and 4 micromeres at the vegetal pole(these divide later).

B. The first tier of micromeres produces the primary mesenchyme cells that later form the larval skeleton, while the second tier of micromeres contributes cells to the coelom(body cavity).

C.Some of the descendents of the small micromeres are shed-off during the development. Since they are shed off during development, their role is not yet known.

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