The moult cycle of the terrestrial isopod Armadillo officinalis Duméril, 1816 (Crustacea: Isopoda: Oniscidea)

The present work focuses on the moult cycle of Armadillo officinalis. For a 100-day period, 134 animals were observed and routinely examined with the aim of detecting distinctive morphological characters in the several stages and substages of the moult cycle and of disclosing their duration. Statistical tests and Poisson regression models with robust standard errors were used to investigate differences and relationships between moult and the size and gender of the animals. The appearance of the calcium carbonate deposits on the pereon sternites during the premoult stage was documented in detail, and three main substages were identified. The average duration of the premoult and of the biphasic ecdysis was about 12 and 1.5 days, respectively. This observation period, however, did not allow to establish a determined average duration of the intermoult stage, which was extremely variable. This stage lasted for 2 months or more in most of the cases observed, but about 1-month- long intermoult stages were also recorded. No statistically significant association was found between the number of moults and gender and size of the animals.