Granivory in terrestrial isopods.

SASKA, PAVEL

Granivory (seed feeding) evolved in many animal groups. Field observations hint at the existence of granivory in terrestrial isopods (Crustacea: Isopoda: Oniscidea), for which it was previously unknown. In this paper granivory in terrestrial isopods is addressed for the first time, focusing on (i) seed acceptance in the presence of plant litter and (ii) size as a constraint for acceptance and consumption. In a laboratory choice experiment, Armadillidium vulgare consumed seeds of Capsella bursa-pastoris and Poa annua when plant litter was present. In a no-choice experiment, seeds of seven plant species were offered to four isopod species giving 13 combinations in total [ A. vulgare (seven species of seeds), Oniscus asellus (two), Porcellio scaber (two), and Porcellionides pruinosus (two)]. The tested isopods differed in their acceptance (proportion of individuals consuming seeds) and consumption (both number and amount of seeds eaten) of seed species. Size as a constraint was demonstrated in A. vulgare offered Cirsium arvense seed, since the probability that this large seed was eaten increased with body size of the isopod. In the other 10 seed–isopod pairs, seed consumption increased linearly with isopod body size. Granivory is thus widespread in terrestrial isopods, although the tendency to eat seeds differs between species.

SEED pods; PLANT litter; HUMUS; LEAF-mold; ORGANIC wastes; ANIMAL morphology; PLANT species; CIRSIUM; CRUSTACEA; ASTERACEAE

Ecological Entomology, 2008, Vol 33, Issue 6, p742

0307-6946

Academic Journal

10.1111/j.1365-2311.2008.01026.x