DEVELOPMENTAL ARREST IN LEPTODACTYLUS-FUSCUS TADPOLES (ANURA, LEPTODACTYLIDAE) .3. EFFECT OF LENGTH OF ARREST PERIOD ON GROWTH-POTENTIAL

Eggs of the neotropical frog Leptodactylus fuscus (Anura: Leptodactyli dae) are laid in foamy masses in burrows close to sites of temporary p ools. After hatching, the tadpoles make a new form of foam and, if no rain falls, enter a kind of developmental arrest. This may last around 30 days after egg deposition. In the experiments reported here, the a bility of tadpoles to grow was tested after different periods of devel opmental arrest in foam nests. In the short term, tadpoles in foam for 15 days grew faster than those in foam 5 or 25 days (these grew at ab out the same rate). However, when raised to metamorphosis, a different pattern emerged. The longer tadpoles remained in foam, the slower the y grew and the smaller the proportion that eventually metamorphosed. T here was considerable variation between nests, with some showing high metamorphic potential 30 days after deposition but others low after on ly 18 days. Unexpectedly, size at metamorphosis varied with time spent in the nest. The longer tadpoles remained in the nest, the larger the ir mean size at metamorphosis, but also the greater their variability in size at metamorphosis. Some of the large tadpoles differed in shape from normal. Tadpoles allowed to grow soon after nest deposition grew rapidly to metamorphose at relatively smaller size and low variabilit y. The significance of these results for the success of the developmen tal arrest strategy is discussed.