Genes and genotypes affecting embryonic fluid relations in the mouse

SUMMARY The contribution of maternal and foetal genotype to the regulation of extra-embryonic (exocoelomic and amniotic) fluid and embryonic fluid in the mouse is discussed. Three of the four inbred strains studied (A, BALB/c and CBA) had similar patterns of fluid accumulation. The fourth (C57BL) differed significantly. In the reciprocalF1crosses between CBA and C57BL a maternal effect was present. In theF2no increase in variance of extra-embryonic fluid was noted. The effects of two mutant genes were studied. Blebs (my) had no effect on the total fluid in the conceptus, but led to a rearrangement of fluid within the embryo. Brachyphalangy (Xtbph) caused an overall increase in fluid within the conceptus. Distribution of the excess depended upon the phenotype (exencephalic versus non-exencephalic) of the embryo.