Receding water levels hasten metamorphosis in the frog, Sphaerotheca breviceps (Schneider, 1799): a laboratory study

Abstract

Gosner stage 19 tadpoles of Sphaerotheca breviceps were exposed to constant or progressively decreasing water levels until metamorphosis with abundant food supply. The tadpoles experiencing constant water levels (column height of 40 mm) reached metamorphic climax (MC) in 35.07 ± 0.44 days and metamorphosed at 39.00 ± 0.43 days at a mean body mass of 409 ± 9.0 mg and 14.64 ± 0.08 mm snout-vent length. In contrast, the larvae experiencing decreasing water levels (from 40 to 12 mm column height) reached Me in 30.93 ± 0.35 days and metamorphosed at 34.73 ± 0.35 days at a significantly smaller body mass and size compared to those reared in constant water levels. In both the treatments survival of tadpoles was 100%. The study reveals that S. breviceps tadpoles are capable of developmental plasticity and with progressive decrease in water levels, the trade-off between growth and development is in favour of development, resulting in early metamorphosis at a small size.