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We investigated how herpetofauna respond to burning and burn season in longleaf pine (Pinus palustris Mill.) sandhills by contrasting preburn species richness, diversity, and evenness and captures of six reptile and six amphibian species to the first (Y+1) or second (Y+2) year after burn or between dormant-season burns (DSB) and growing-season burns (GSB). Responses to burning overall or burn season were inconsistent among species; several showed no response, whereas others responded positively or negatively. Most responses were evident only in Y+1. Reptile species richness, diversity, and evenness responses were not detected. Amphibian richness increased after burning overall; diversity and evenness decreased more in GSB than in DSB in Y+1. Southern toad (Anaxyrus terrestris (Bonnaterre, 1789)) captures increased and Florida crowned snake (Tantilla relicta Telford, 1966) captures decreased following burns overall in Y+1. Ground skink (Scincella lateralis (Say in James, 1823)) captures increased more in DSB than GSB in Y+1. Florida gopher frog (Lithobates capito (LeConte, 1855)) and southeastern five-lined skink (Plestiodon inexpectatus; Taylor, 1932) captures increased, and oak toad (Anaxyrus quercicus (Holbrook, 1840)) decreased more in GSB than DSB in Y+2. Responses were likely due to changes in aboveground activity affecting captures or (for amphibians especially) annual variability in captures unrelated to burns. Our results indicated that reptiles and amphibians of sandhills are resilient to short-term effects of burning overall and burn season. Key words: amphibians, dormant-season burns, growing-season burns, longleaf pine--wiregrass sandhills, prescribed fire, reptiles, sandhills, season of burn. Nous avons etudie de quelle facon l'herpetofaune reagit au brulage et a la saison durant laquelle a lieu le brulage dans les communautes de pin des marais (Pinus palustris Mill.) etablies sur des collines sableuses. Nous avons compare l'uniformite, la diversite et la richesse en especes ainsi que les captures de six especes de reptiles et six especes d'amphibiens avant un brulage et un ou deux ans apres le brulage. Nous avons aussi compare les effets du brulage durant la periode de dormance (BPD) et du brulage durant la saison de croissance (BSC). Dans l'ensemble, les reactions au brulage ou au moment oU il a ete effectue ont varie selon l'espece; plusieurs n'ont eu aucune reaction et d'autres ont reagi soit positivement, soit negativement. La plupart des reactions etaient evidentes seulement apres un an. Aucune reaction de l'uniformite, de la diversite et de la richesse en especes de reptiles n'a ete detectee. La richesse des amphibiens a generalement augmente apres un brulage; apres un an, l'uniformite et la diversite avaient davantage diminue avec le BSC qu'avec le BPD. Les captures du crapaud criard (Anaxyrus terrestris (Bonnaterre, 1789)) ont augmente et celles de la couleuvre couronnee de Floride (Tantilla relicta Telford, 1966) ont diminue un an apres l'ensemble des brulages. Dans l'annee qui a suivi, les captures du scinque brun mineur (Scincella lateralis (Say in James, 1823)) ont davantage augmente apres un BPD qu'apres un BSC. Les captures de la grenouille des terriers (Lithobates capito (LeConte, 1855)) et du scinque pentaligne du sud-est (Plestiodon inexpectatus Taylor, 1932) ont augmente et celles du crapaud des chenes (Anaxyrus quercicus (Holbrook, 1840)) ont davantage diminue deux ans apres le brulage a la suite d'un BSC qu'a la suite d'un BPD. Les reactions etaient probablement dues aux changements dans l'activite au-dessus du sol qui influencaient les captures, ou (surtout dans le cas des amphibiens) a la variation annuelle des captures non reliee au brulage. Nos resultats indiquent que les reptiles et les amphibiens des collines sableuses sont en general resilients face aux effets a court terme du brulage et du moment oU est effectue le brulage. [Traduit par la Redaction] Mots-cles : amphibiens, brulage durant la periode de dormance, brulage durant la saison de croissance, communautes de pin des marais et d'aristide des pinedes etablies sur des collines sableuses, brulage dirige, reptiles, collines sableuses, saison durant laquelle le brulage a lieu., 1. Introduction Many reptile and amphibian species are endemic to the endangered longleaf pine (Pinus palustris Mill.)--wiregrass (Aristida stricta Michx.) sandhill ecosystem (Means and Grow 1985). Longleaf pine once occupied [...]

ABSTRACT. The conservation status of Crawfish Frogs (Lithobates areolatus) in Indiana has changed over the past several decades. Once described as being locally plentiful, declines led to the listing of [...]

Alkaloids in the skin glands of poison frogs serve as a chemical defense against predation, and almost all of these alkaloids appear to be sequestered from dietary arthropods. Certain alkaloid-containing ants have been considered the primary dietary source, but dietary sources for the majority of alkaloids remain unknown. Herein we report the presence of [approximately equal to] 80 alkaloids from extracts of oribatid mites collected throughout Costa Rica and Panama, which represent 11 of the [approximately equal to] 24 structural classes of alkaloids known in poison frogs. Forty-one of these alkaloids also occur in the dendrobatid poison frog, Oophaga pumilio, which co-occurs with the collected mites. These shared alkaloids include twenty-five 5,8-disubstituted or 5,6,8-trisubstituted indolizidines; one 1,4-disubstituted quinolizidine; three pumiliotoxins; and one homopumiliotoxin. All but the last of these alkaloid classes occur widely in poison frogs. In addition, nearly 40 alkaloids of unknown structure were detected in mites; none of these alkaloids have been identified in frog extracts. Two of these alkaloids are homopumiliotoxins, five appear to be izidines, four appear to be tricyclics, and six are related in structure to poison frog alkaloids that are currently unclassified as to structure. Mites are common in the diet of O. pumilio, as well as in the diets of other poison frogs. The results of this study indicate that mites are a significant arthropod repository of a variety of alkaloids and represent a major dietary source of alkaloids in poison frogs. chemical defense | dendrobatid frogs | indolizidines | myrmicine ants | pumiliotoxins

The accuracy of amphibian call counts in the field is assessed by monitoring a protocol for amphibians in the Rainwater Basins of Nebraska and documented observer bias. The results have shown that high and unquantified error rates might negatively affect the ability of monitoring programs to accurately detect the population or abundance trends.

Chytridiomycosis caused by chyrid fungus have been detected in seven out of nine amphibian species in Maine, mostly common in green frogs. Lower incidences of infections were found in species hibernating in terrestrial habitats than those hibernating in aquatic habitat.

Developmental plasticity is found in most organisms, but its role in evolution remains controversial. Environmentally induced phenotypic differences may be translated into adaptive divergence among lineages experiencing different environmental conditions through genetic accommodation. To examine this evolutionary mechanism, we studied the relationship between plasticity in larval development, postmetamorphic morphology, and morphological diversity in spadefoot toads, a group of closely related species that are highly divergent in the larval period and body shape and are distributed throughout temperate areas of both the New and the Old World. Previous studies showed that accelerated metamorphosis is adaptive for desert-dwelling spadefoot toads. We show that even under common garden conditions, spadefoot toad species show divergent reaction norms for the larval period. In addition, experimentally induced changes in the larval period caused correlated morphological changes in postmetamorphic individuals such that long larval periods resulted in relatively longer hindlimbs and snouts. A comparative analysis of morphological variation across spadefoot toad species also revealed a positive correlation between the larval period and limb and snout lengths, mirroring the effects of within-species plasticity at a higher taxonomic level. Indeed, after [approximately equal to] 110 Ma of independent evolution, differences in the larval period explain 57% of the variance in relative limb length and 33% of snout length across species. Thus, morphological diversity across these species appears to have evolved as a correlated response to selection for a reduced larval period in desert-dwelling species, possibly diverging from ancestral plasticity through genetic accommodation. allometry | genetic accommodation | life-history evolution | morphological diversity I larval period

The recent experiments in Hu et al. (Am J Physiol Heart Circ Physiol 279: H1724-H1736, 2000) and Adamson et al. (J Physiol 557: 889-907, 2004) in frog and rat mesentery microvessels have provided strong evidence supporting the Michel-Weinbaum hypothesis for a revised asymmetric Starling principle in which the Starling force balance is applied locally across the endothelial glycocalyx layer rather than between lumen and tissue. These experiments were interpreted by a three-dimensional (3-D) mathematical model (Hu et al.; Microvasc Res 58: 281-304, 1999) to describe the coupled water and albumin fluxes in the glycocalyx layer, the cleft with its tight junction strand, and the surrounding tissue. This numerical 3-D model converges if the tissue is at uniform concentration or has significant tissue gradients due to tissue loading. However, for most physiological conditions, tissue gradients are two to three orders of magnitude smaller than the albumin gradients in the cleft, and the numerical model does not converge. A simpler multilayer one-dimensional (1-D) analytical model has been developed to describe these conditions. This model is used to extend Michel and Phillips's original 1-D analysis of the matrix layer (J Physiol 388: 421-435, 1987) to include a cleft with a tight junction strand, to explain the observation of Levick (Exp Physiol 76: 825-857, 1991) that most tissues have an equilibrium tissue concentration that is close to 0.4 lumen concentration, and to explore the role of vesicular transport in achieving this equilibrium. The model predicts the surprising finding that one can have steady-state reabsorption at low pressures, in contrast to the experiments in Michel and Phillips, if a backward-standing gradient is established in the cleft that prevents the concentration from rising behind the glycocalyx. endothelial glycocalyx; tight junction; capillary permeability; vesicular transport

Neotropical poison frogs (Dendrobatidae) contain a variety of lipophilic alkaloids in their diffusely distributed cutaneous glands, including a major class of compounds known as pumiliotoxins. Pumiliotoxins are highly toxic and are believed to protect frogs against predators. Their potential activity against ectoparasites, however, has not been investigated. We tested female yellow fever mosquitoes (Aedes aegypti) for responses to 8-hydroxy-8-methyl -6-(2'-methylhexylidene)-1-azabicyclo[4.3.0]nonane, designated pumiliotoxin 251D [PTX (+)-251D], a skin alkaloid present in all genera of dendrobatids and in other anurans, and to its unnatural enantiomer, PTX (-)-251D. Both enantiomers of PTX 251D presented on silicone feeding membranes reduced landing and feeding by A. aegypti, but PTX (+)-251D did so at lower concentrations. PTX (+)-251D also induced toxicosis, shown when mosquitoes failed to fly off membranes. Similarly, mosquitoes confined with copper wires coated with PTX (+)-251D exhibited greater latencies to fly off the substrate and a higher incidence of leg autotomy than did those confined with the (-)-enantiomer. Our results on the contact toxicities of PTX 251D enantiomers parallel those reported for mice injected with them. The presentation of serial dilutions of PTX (+)-251D to A. aegypti revealed a minimum toxic concentration of 0.1 [micro]g/[cm.sup.2]. This value is substantially lower than that estimated for the cutaneous abundance of this compound in some frogs, an observation consistent the function of PTX 251D in anuran chemical defense against ectoparasitic arthropods. alkaloids | chemical defense | dendrobatid poison frogs | insecticidal activity | skin secretions