Scerotization

This is the conversion of soft proteinaceous materials to harder and resistant layers in oocysts of coccidia, in worm eggs, cocoons, or in other cystlike structures that have contact with the environment. Two main processes may lead to sclerotization: quinone-tanning and dityrosine cross-linking. Quinone tanning occurs, e.g., in egg capsules, eggshells of trematodes, insect cuticle, while protein-dityrosine cross-links are found in yeast cell wall, insect resilin, and coccidian oocysts.