Rate of Cocoon Formation and Its Physiological Correlates in a Ceratophryd Frog

Lepidobatrachus llanensis, a ceratophryd frog from the Argentine Chaco, develops a cocoon composed of multiple layers of epidermis when kept out of water. Active toads, in water, have a mean shedding cycle (intermolt period) of 1.6 days. During cocoon formation the toads produce one new layer of one-cell-thick stratum corneum per day. Cocoon formation represents a behavioral mechanism that suppresses the motor responses that normally cause the shedding of the old stratum corneum. Concomitant with cocoon formation, evaporative water loss decreases dramatically (EWL 10 mg g⁻¹ h⁻¹ to < 1 mg g⁻¹ h⁻¹). Resistance to water flux in cocooned Lepidobatrachus is comparable to other cocooned and "waterproofed" frogs (50-500 s cm⁻¹). Each layer of the cocoon contributes 3 s cm-¹ to the cutaneous resistance. During cocoon formation, oxygen consumption decreases rapidly (V̇o2 at 25 C, .06 ml g⁻¹ h⁻¹ to .01 ml g⁻¹ h⁻¹).