Trichuris muris: structure and formation of the egg-shell

Abstract

SummaryThe development of the egg-shell of the trichuroid nematode, Trichuris muris, was observed by light and electron microscopy. Initial stages of shell formation occurred immediately following sperm entry into the oocyte in the spermatheca of the female worm. The external vitelline layer separated from the oolemma, reticulate oocyte granules were discharged into the resultant perivitelline space and stored glycogen contributed to the formation of the chitinous shell. A lipid layer developed between the inner surface of the chitinous layer and the oolemma. The fully formed egg-shell thus comprised an external vitelline layer, a middle chitinous layer and an inner lipid layer. The outer vitelline layer resembled a unit membrane with strands of particulate material attached to its outer surface. The middle chitinous layer was composed of chitin microfibrils encased in a protein coat; the sheets of microfibrils were arranged as parallel lamellae forming a helicoidal architecture. The inner lipid layer contained a variable number of loosely arranged strands of electron-opaque and less-opaque material.