Fig. 5. Comparison of cyk-3 embryos and wild-type embryos under different
osmotic conditions. Embryos were dissected into EGM containing the vital dyes
FM4-64 and calcein. FM4-64 stains membranes; calcein is a marker for viability
(shown in the insets). 0.5x, 1x and 2x EGM refer to the
increasing concentration of stock salts in the medium. (a) In hypotonic
medium, wild-type and cyk-3 embryos appear swollen, with few cleavage
furrows. (b) In 1x EGM, under isotonic conditions, wild-type embryos
have normal morphology; they neither shrink nor swell. By contrast,
cyk-3 embryos remain swollen, showing no difference from wild-type or
cyk-3 embryos observed in 0.5x EGM (compare with a). (c) In
hypertonic medium, wild-type embryos respond to the higher ion concentration
by shrinking. cyk-3 embryos under the same conditions do not shrink
but collapse. The collapsing does not involve membrane invaginations, since
the ingression observed at the surface of the embryo does not correspond to
membrane staining.
