Quantitative estimation of chitin and proteins in the cuticle of five species of Priapulida

The biochemical composition ofthe cuticle of 5 species of Priapulida was tested using a specific enzymatic method for the determination of chitin, and a lectin-labelling technique for its ultrastructural location. The integument of all species tested contains 4–15 % chitin and 9–85 % protein. Chitin could be located in both layers of the priapulid cuticle, even though their ultrastructural morphology differs. The results of this work suggest a close relationship between the Priapulida and the Kinorhyncha, the only other group of Aschelminths known to have a chitinous cuticle.