Cell Size Critical for Morphogenesis

Cell size can be deadly critical for morphogenesis. In Drosophila, embryos lacking the product of the string gene do not undergo cell divisions following the thirteenth mitotic cycle. For a while, this defect does not cause any problem. Following cellularisation of the originally syncytial blastoderm, string embryos undergo a noticeable degree of morphogenesis and tissue differentiation. However, at a later stage, they fail to gastrulate, due to the excessive size of their cells which cannot undergo the normal movements necessary for gastrulation (Foe 1989).

A correct cell size, however, is not simply a mechanical requirement for normal development. In a more subtle sense, cell size is often the grain of organic form. Organs or organisms composed of cells of smaller size may attain higher complexity than comparable organs or organisms whose cells are larger. A beautiful example is provided by the variation in cell size and overall complexity of the tectum mesencephali, the main visual centre in amphibians. Frogs with small cells have a tectum with more complex morphology than those with large cells; this is independent of body and brain size.