A crossover design to assess feeding preferences in terrestrial isopods: a case study in a Mediterranean species

A crossover design was used to study food preferences and capability of nutritional acclimation to different food sources in terrestrial isopods, which live in xeric environments, by using Armadillo officinalis as an experimental model. The foods chosen for this experiment were three fresh foods with different content of water (potato, carrot, lettuce), and a dry food (leaf of plane tree). In order to quantify these preferences, two kinds of data able to provide complementary information were collected: number of droppings produced and food ingested per week. These data were used to fit some mixed effects models, in order to highlight statistically significant differences among the foods provided to the animals at a level of preferences. In addition, the buccal appendages of A. officinalis were observed and drawn in details, to provide further information at this level. Our results showed that A. officinalis seems not to have particular preferences between fresh foods with a moderate quantity of water and dry food, commonly eaten in its natural habitat. In contrast, foods with high quantity of water, like the lettuce, seem not to be instead particularly palatable for its taste, or its nutritional needs. Also, this study seems to have highlighted a better capability of digestion and absorption of the potato tuber compared to the leaf of plane tree for an equal quantity of ingested food. Anyway, this hypothesis needs further insights in order to be able to be verified.