Water-balance response of Rhinella arenarum (Hensel, 1867) tadpoles to graduated increase in environmental osmolarity

FERRARI, L.; FERNANDO ROMAN DE LA TORRE; SALIBIÁN, A.

BRAZILIAN JOURNAL OF BIOLOGY

INT INST ECOLOGY

Lugar: Sao Carlos Brasil; Año: 2010 vol. 70 p. 171 - 179

1519-6984

The water balance and the upper limit of osmotic tolerance of premetamorphic Rhinella arenarum larvae (Gosner’s stage 26) was evaluated after semistatic incubation in electrolyte (NaCl) and non-electrolyte (mannitol) media followinga protocol of progressively increased osmotic pressure. Wet and dry weights were measured to calculate the water content as a derived variable indicative of the hydric balance. Statistical analysis was performed using univariate and integrated multivariate analysis. Tadpoles survived in electrolyte and non-electrolyte solutions up to 200 mOsm. The discriminant function was the best tool to describe the responses of the animals to external environmental stress under experimental conditions. The results were compared with those obtained in previous studies using a protocol of acute exposure to the same media used in this study. It was concluded that a) multivariate analysis is an appropriate approach to describe the responses of tadpoles to changes in the environmental physicochemical parameters, and b) progressive and acute acclimation to the experimental solutions induced similar responses.