The morphology and histochemistry of eggshell formation in Cephaluris coloradensis, a parasite of pikas.

Histochemical and histological studies of Cephaluris coloradensis (Nematoda: Oxyuridae) a parasite of pikas (Ochotonidae), show that in this species the eggs are each enclosed by three shells. The inner shell is chitin with an operculum at one end; the operculum is chemically distinct. The other two shells are lipoprotein. The inner lipoprotein shell is new, not previously reported in nematode species. It forms after the outer lipoprotein shell but beneath it, and is believed to be a product of the egg. The new layer encircles part of the embryo. A thin mucoprotein cementing substance binds the inner lipoprotein shell to the chitinous shell. A thin outermost mucoprotein layer formed from secretions of the uterus covers the eggshell.