Authors: Rafael Márquez, Daniel Cejudo And Valentín Pérez-mellado

Authors: Geoffrey R. Smith

Authors: D. Taylor And L. Winder

Authors: John Davenport And Khoo Khay Huat

Authors: Marc Augé

Authors: Arturo I. Kehr

Abstract: An analysis of major demographic characteristics of a cohort of Pseudacris ocularis tadpoles was performed under natural conditions. The study was carried out in a temporary pond within the Lower Suwannee National Wildlife Refuge, in Florida, USA. Five developmental stage groups were established. Several samples were taken at different times during development of the cohort. The pond water-level was nearly constant throughout the study. The main results obtained were: (I) the mean time to metamorphosis was 7.3 1 d; (2) the tadpoles spent more time at stages 33-36 (2.42 d) than at other stages; (3) the shortest developmental stages were 25-28 (only 0.99 d); ( 4) the survival rate was 1 0.3%; (5) the range of the survival rate for the five stage groups was 47. 1 -73 .6%; (6) the estimated unit time survival rate was 73.3%; (7) the life expectancy (e(x)) for a tadpole just hatched was 3 .07 d; (8) the survival curve (l(x)) was comparable to a Type II curve; and (9) the value of H (entropy) was 0.824. The tadpoles spent more time at the periphery than in the centre of the pond. Significant differences in water temperatures between the peripheral and central sampling units were observed.

Authors: Michaels. Y. Lee

Abstract: On the basis of an extensive set of visceral and scale characters, Wallach (1985) proposed a detailed phylogenetic scheme for all the Australian elapids, down to species level. The shortest tree found in that analysis is here shown to contain 592 steps. However, a re-analysis of the same data using PAUP 3.1.1 reveals that there are 258 most parsimonious trees, each with only 578 steps. The strict consensus of these trees is much less resolved than Wallach 's tree, and has a different topology. For example, Echiopsis is most closely related to Sutafasciata rather than to the Notechis lineage, and Dernansia is more closely related to advanced elapids (such as the Notechis lineage) than to Oxyuranus and Pseudonaja. Many of the larger (suprageneric) groupings proposed by Wallach are paraphyletic in the PAUP consensus tree. Almost all the groupings in this tree, however, can be collapsed with the addition of a single extra step. There are more than 32 OOO cladograms at 579 steps, one step longer than the 258 most parsimonious cladograms. A strict consensus tree of cladograms 578 and 579 steps long is almost completely unresolved. The visceral and external morphological traits, therefore, are not as phylogenetically informative as previously proposed, at least with respect to the Australian elapid radiation. These types of characters might not be very phylogenetically informative at higher (intergeneric) levels, although much more data are required to test this hypothesis.

Authors: J. R. Downie And A. Weir

Abstract: Eggs of the neotropical frog Leptodactylus fuscus (Anura: Leptodactylidae) are laid in foamy masses in burrows close to sites of temporary pools. 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 ability of tadpoles to grow was tested after different periods of developmental 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 about the same rate). However, when raised to metamorphosis, a different pattern emerged. The longer tadpoles remained in foam, the slower they grew and the smaller the proportion that eventually metamorphosed. There was considerable variation between nests, with some showing high metamorphic potential 30 days after deposition but others low after only 18 days. Unexpectedly, size at metamorphosis varied with time spent in the nest. The longer tadpoles remained in the nest, the larger their 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 variability. The significance of these results for the success of the developmental arrest strategy is discussed.