The presence of α-chitin in Tardigrada with comments on chitin in the Ecdysozoa

We used Fourier Transform Infrared Spectroscopy (FT-IR) to characterize for the first time chitin in the cuticle of a eutardigrade (Macrobiotus cf. hufelandi). Analysis of the isolated cuticles of single individuals and comparison with commercial α-chitin isolated from shrimp shell and β-chitin from squid pen revealed that the amide I band was split into two peaks characteristic for α-chitin. In the current literature cuticles containing α-chitin are considered as an apomorphic character of the Ecdysozoa (Cycloneuralia, Panarthropoda). This is a plausible assumption, although α-chitin has been unequivocally demonstrated only in the cuticle of the Panarthropoda, i.e. Onychophora, Tardigrada (this article) and Arthropoda, and in the Priapulida (Cycloneuralia), whereas chitin in the cuticle of the other cycloneuralian taxa either was not further specified or appears to be absent.