Structural differences in the egg envelopes of Haemonchus contortus and Trichostrongylus colubriformis (Nematoda: Trichostrongylidae)

Many studies have been carried out on the structure and chemical composition of trematode and cestode egg envelopes. Among the nematodes, much work has been done on the eggs of ascarids but there have been few studies on the egg envelopes of species in the Superfamily Trichostrongyloidea. Zawadowsky et al. (1929) reported on the biology of five species of this family, namely Trichostrongylus instabilis (T. colubriformis), T. extenuatus (T. axei), T. probolurus, Cooperia pectinata and Ostertagia mentulata. They described the egg envelope as consisting of three or possibly four layers. The physical and chemical properties of these layers were investigated and these workers concluded that the structure of the egg envelope was similar to that of Ascaris. However, the solubility of the inner layer differed from that of Ascaris in dissolving only partially in absolute alcohol and very little in ether.