VARIATION IN ULTRASTRUCTURE OF MUCOID COAT AND SHELL MEMBRANE SECRETION OF A DASYURID MARSUPIAL

In the dasyurid marsupial Sminthopsis crassicaudata, the shell membran e of cleaving embryos has a compact granular structure but becomes fib rous around blastocysts. Polyclonal antibodies were raised against the extracellular coats, mucoid and shell membrane, of oocytes and early embryos, Immunogold cytochemistry resulted in labelling of secretory g ranules in the epithelia of both the ampulla and isthmus of the oviduc t, although the secretory granules of these two regions differed in th eir ultrastructural appearance. Those in the ampulla were heterogeneou s with areas of varying electron density, whereas those in the isthmus were electron dense and homogeneous. Shell membrane precursors were f ound in secretory granules in the epithelia of the uterotubal junction and endometrial glands and were electron lucent.