RESPIRATION OF EMBRYOS AND LARVAE OF THE TERRESTRIALLY BREEDING FROG KYARRANUS LOVERIDGEI

Abstract

The Australian leptodactylid frog Kyarranus loveridgei deposits its eggs in a flask- shaped depression in moist soil, where they hatch and undergo metamorphosis within the jelly mass. The average non-foamy egg mass occupies 10.35 cm3 at the bottom of the depression, and the 3-mm eggs are in two layers, with about 22 in the top layer and nine below. Embryos in the top layer hatch at Gosner stage 18-20, when they are exposed to an average oxygen partial pressure (Po2) of 14 kPa in the jelly around them, and when their total oxygen consumption averages 1.5 ttl/h at 20 C. Embryos in the bottom layer are exposed to an average Po, of about 7.6 kPa and, failing to hatch, they eventually die. Hatched larvae move to the surface of the jelly and lash their tails periodically, which mixes oxygen-rich jelly around them. They survive on gill and cutaneous respiration until they begin to gulp air at stage 30, when their oxygen uptake reaches 5 ,ul/h. High mortality due to oxygen starvation in the lower embryos is associated with the lack of bubbles in the egg mass, although the females have flanges on their fingers that are used by related species to produce a foam nest.