Oxygen consumption of a large, cold-adapted frog egg (Ascaphus truei (Amphibia: Ascaphidae))

Abstract

Female Ascaphus lay a small number of large eggs beneath rocks in cold, montane streams of the Pacific Northwest. Average number of eggs per female is 45 (range, 28 to 64) and average egg diameter is 4 mm (range, 3.5 to 4.5). The large eggs of Ascaphus contain a relatively large amount of nutrients. Average wet weight of a single egg is 37.5 mg and dry weight is 23.7 mg (63% of wet weight). The oxygen consumption rate of embryos during development at 15 °C increases gradually during cleavage (0.25 μl O2/h per embryo) and more rapidly during neurula and postneurula stages (0.60 to 0.90 μl O2/h per embryo) to a value of 1.20 μl O2/h per embryo at vitelline circulation. The cold-adapted eggs of Ascaphus are characterized by large size, slow developmental rate and low oxygen consumption rate.