Stage-specific changes in membrane microviscosity in <Emphasis Type="Italic">Misgurnus fossilis</Emphasis> embryos

Natural and probe fluorescence as well as membrane microviscosity was studied in eggs and embryos of Misgurnus fossilis by fluorescence microscopy. The lateral mobility of the probe (pyrene) increased in loach embryos from early to late blastula, which indicates a decrease in plasma membrane microviscosity. At the later stage of mid-gastrula, the microviscosity remained largely invariant. Considering that the embryo exposure to different temperatures changes the quantum yield of fluorescence and the degree of pyrene excimerization, one can gain information about both the temperature-induced structural changes and changes in membrane microviscosity in the embryos. Natural and probe fluorescence of embryonic membranes is proposed as at tool to study morphogenetic mechanisms.