[Intra-and interspecific crowding-effects in tadpoles ofBufo calamila Laur.].

Tadpoles ofBufo calamita, a species that spawns in little temporary pools, were tested on intra- and interspecific crowding-effects. Water was conditioned by tadpoles of the following species:Bufo calamita (tadpoles of different age),Alytes obstetricans, Bombina variegata, Bufo bufo, Hyla arborea, Rana lessonae, R. ridibunda andR. temporaria. Tadpoles ofBufo calamita are most sensitive to water conditioned by older tadpoles of the own species during the first 2-3 weeks of development. They are also strongly inhibited by tadpoles ofRana temporaria andBufo bufo (that, as a rule, do not occur in the same habitat). Relative little effects are observed in water conditioned by tadpoles of the two species that occur very often in ecological sympatry withBufo calamita: Hyla arborea andBombina variegata. Young tadpoles ofBufo calamita are most tolerant of tadpoles of the same age of the own species. The crowding-effect increases with the number and weight of tadpoles/volume conditioning the water. In the age of 2-3 weeks the sensibility to intra- and interspecific crowding-effects fades. Thus inBufo calamita the age specific sensibility to crowding-effects in tadpoles may act as a density regulation mechanism in temporary pools.