Marcos Vaira

Annual variation of breeding patterns of the toad, Melanophryniscus rubriventris (Vellard, 1947)

Climate may play a direct role in determining patterns of reproductive activity in anurans. Investigating the responses of males and females attending a breeding site to environmental variation are of particular interest regardless the possible effect of climate change on the decline of populations. I studied annual variation over two years in the breeding population size and breeding phenology of the diurnal toad, Melanophryniscus rubriventris, in a seasonal environment characterized by temporal and spatial uncertainty due to climatic conditions. Breeding activity of this toad was opportunistic throughout a prolonged spring-summer breeding season. Direct influence of rainfall on the onset and extent of breeding activity was detected in both years. Spawning activity showed a clear pattern of two three-day peaks mostly related to heavy rainfall events. Males always significantly outnumbered females at breeding sites. The disparity of rainy season extent between the two breeding seasons studied resulted in different annual patterns of arrival and length of residence of adults. Males and females remained several days longer during the second year than during the first year. Because adults showed highly variable annual patterns of breeding activity studies involving only a few years may yield misleading results concerning the nature and extent of the decline of the species or populations. Future studies on the ecology and conservation of the species should include long-term monitoring.

A new species of Elachistocleis (Anura: Microhylidae) from the Andean Yungas of Argentina, with comments on the Elachistocleis ovalis - E. bicolor controversy

Elachistocleis skotogaster spec. nov. is described from the Andean Yungas of Argentina. It is unique in the genus in having belly and legs densely spotted with brown, an uniformly dark brown dorsal mottled with black, absence of alight vertebral strip, afold behind themouth but not apostcommisural gland. Itsnatural history and advertisement call are briee y noted. Elachistocleis ovalis and E.bicolor are considered different species, and Buenos Aires, Argentina, is established as type locality for the latter one.

Breeding biology of the leaf frog, Phyllomedusa boliviana (Anura, Hylidae)

Spawning behavior, clutch characteristics, and egg deposition site of the leaf frog, Phyllomedusa boliviana , were described at an artificial pool in a subtropical montane forest of Jujuy, Argentina. Mating behavior was observed during the wet season (November-January) in unmarked frogs on eight separate occasions. A prespawning period characterized by repeated struggles between amplexed and unamplexed males for possession of the female was observed lasting from 2 to 4 hours. The entire sequence of leaf folding and extrusion of both eggless capsules and eggs occurred in less than 30 minutes. After the pair separated, the female remained at the top of the leaf nest extruding a mass of eggless capsules leaving the nest 22-70 min later. Egg masses were deposited every month of the breeding season on almost every plant species at the pool perimeter, but P.boliviana appeared to choose certain species. Deposition heights between 5 and 35 cm occurred most frequently and heights above 100 cm were uncommon. The results of this study indicate that P. boliviana is able to breed in artificial ponds, information that could be useful in the management of altered habitats.

Alkaloids from single skins of the Argentinian toad Melanophryniscus rubriventris (ANURA, BUFONIDAE): An unexpected variability in alkaloid profiles and a profusion of new structures

GC-MS analysis of single-skins of ten Melanophryniscus rubriventris toads (five collections of two toads each) captured during their breeding season in NW Argentina has revealed a total of 127 alkaloids of which 56 had not been previously detected in any frog or toad. Included among these new alkaloids are 23 new diastereomers of previously reported alkaloids. What is particularly distinguishing about the alkaloid profiles of these ten collections is the occurrence of many of the alkaloids, whether known or new to us, in only one of the ten skins sampled, despite two skins being obtained from each breeding site of the five populations. Many of the alkaloids are of classes known to have structures with branched-chains (e.g. pumiliotoxins and tricyclic structures) that are considered to derive from dietary mites. A large number of previously reported and new alkaloids are also of unclassified structures. Only a very few 3,5-disubstituted-indolizidine or -pyrrolizidine alkaloids are observed that have a straight-chain carbon skeleton and are likely derived from ant prey. The possible relationship of these collections made during the toad’s brief breeding episodes to sequestration of dietary arthropods and individual alkaloid profiles is discussed.

Population diet variation and individual specialization in the poison toad, Melanophryniscus rubriventris (Vellard, 1947)

Few studies have investigated the level of individual variation in diet composition of poisonous frogs and toads. We compare the diet composition of three populations of a poisonous toad, Melanophryniscus rubriventris , and predicted that toads within a population might be constrained to forage on particular types of alkaloid-containing prey and consequently diets among populations might not diverge from each other. Most important prey categories in the diets of the three populations consisted of the same ground-dwelling arthropods. We found evidence for individuals consuming different arrays of prey types in all populations implying that this “generalist” species is actually comprised of individuals eating different sets of the available range of prey. Formicidae, Acari, and Coleoptera were all important alkaloid-containing prey items in the diets of all populations and individuals, although there were differences in their order of importance among populations and individuals use different sets of the entire range of alkaloid-containing preys. Future research should evaluate individual diet variation in other poisonous anurans taxa given that shifts in diet composition might have important implications for understanding the consequences of alternate foraging strategies in the evolution of defensive strategies among species.

Figure 1 In A New Species Of Elachistocleis (Anura: Microhylidae) From North-Western Argentina

FIGURE 1. Elachistocleis haroi sp. nov., holotype (FML 24900), dorsal and ventral views of body, and head profile. White bar 1 cm.