Edmund D. Brodie

Increased frequency and severity of developmental deformities in rough-skinned newt (Taricha granulosa) embryos exposed to road deicing salts (NaCl & MgCl2).

Road-side aquatic ecosystems in North America are annually polluted with millions of tons of road deicing salts, which threaten the survival of amphibians which live and breed in these habitats. While much is known of the effects of NaCl, little is known of the second most-commonly used deicer, MgCl(2), which is now used exclusively in parts of the continent. Here we report that environmentally relevant concentrations of both NaCl and MgCl(2) cause increased incidence of developmental deformities in rough-skinned newt hatchlings that developed embryonically in these salts. In addition, we provide some of the first quantification of severity of different deformities, and reveal that increased salt concentrations increase both deformity frequency and severity. Our work contributes to the growing body of literature that suggests salamanders and newts are particularly vulnerable to salt, and that the emerging pollutant, MgCl(2) is comparable in its effects to the more traditionally-used NaCl.

The role of corticosterone and toxicity in the antipredator behavior of the Rough-skinned Newt (Taricha granulosa).

A variety of mechanisms are responsible for enabling an organism to escape a predatory attack, including behavioral changes, alterations in hormone levels, and production and/or secretion of toxins. However, these mechanisms are rarely studied in conjunction with each other. The Rough-skinned Newt (Taricha granulosa) is an ideal organism to examine the relationships between these mechanisms because its behavioral displays and toxin secretion during a predator attack are well documented and readily characterized. While we found no direct relationship between antipredator behavior and endogenous levels of corticosterone (CORT), antipredator behavior was inhibited when exogenous CORT and adrenocorticotropic hormone (ACTH) were administered, resulting in high circulating concentrations of CORT, indicating that CORT may play a role in mediating the behavior. There was no correlation between the animals toxicity and either CORT or behavior. The results of this study provide evidence that CORT plays an important, yet complex, role in the antipredator response of these amphibians.

Physiological Responses to Salinity Vary with Proximity to the Ocean in a Coastal Amphibian

Freshwater organisms are increasingly exposed to elevated salinity in their habitats, presenting physiological challenges to homeostasis. Amphibians are particularly vulnerable to osmotic stress and yet are often subject to high salinity in a variety of inland and coastal environments around the world. Here, we examine the physiological responses to elevated salinity of rough-skinned newts (Taricha granulosa) inhabiting a coastal stream on the Pacific coast of North America and compare the physiological responses to salinity stress of newts living in close proximity to the ocean with those of newts living farther upstream. Although elevated salinity significantly affected the osmotic (body weight, plasma osmolality), stress (corticosterone), and immune (bactericidal ability) responses of newts, animals found closer to the ocean were generally less reactive to salt stress than those found farther upstream. Our results provide possible evidence for some physiological tolerance in this species to elevated salinity in coastal environments. As freshwater environments become increasingly saline and more stressful, understanding the physiological tolerances of vulnerable groups such as amphibians will become increasingly important to our understanding of their abilities to respond, to adapt, and, ultimately, to survive.

TAXONOMIC REVISION OF THE MEXICAN PLETHODONTID SALAMANDERS OF THE GENUS LINEATRITON, WITH THE DESCRIPTION OF TWO NEW SPECIES

We describe two new species of salamanders of the genus Lineatriton, which occur as allopatric populations in the Sierra de Juárez, Oaxaca, and the Sierra de Los Tuxtlas, Veracruz, Mexico. The name Lineatriton lineolus (Cope) is restricted to populations in the Sierra Madre Oriental of Veracruz. The population in the Sierra de Los Tuxtlas, previously allocated to L. lineolus, is here described as Lineatriton orchimelas. The population from the Sierra de Juárez is reported here for the first time and is described as yet another new species of Lineatriton. These new species differ from L. lineolus in aspects of body size, body proportions, and pigmentation of the male reproductive organs. Resumen Se describe dos especies de salamandra del género Lineatriton de las vertientes húmedas de Veracruz y Oaxaca, México. Las nuevas especies se conocen de poblaciones alopátricas de la Sierra de Juárez y la Sierra de Los Tuxtlas. Previamente estas poblaciones fueron referidas como Lineatriton lineolus. Lineatriton lineolus se restringe a poblaciones en la Sierra Madre Oriental, Veracruz. Las nuevas especies difieren de L. lineolus por presentar tamaños de cuerpo diferentes y en la coloración de los órganos de reproducción en machos.

Mutations to the cardiotonic steroid binding site of Na(+)/K(+)-ATPase are associated with high level of resistance to gamabufotalin in a natricine snake.

Although toads are defended by bufadienolide toxins, some snakes have evolved resistance to bufadienolides and feed heavily on toads. We compared resistance in Nerodia rhombifer, which possesses mutations that confer target-site resistance, to Pituophis catenifer, which lacks those mutations. Even at the highest dosage tested, Nerodia showed no effects, whereas the lowest dose was lethal to Pituophis. Our results demonstrate a striking level of resistance to bufadienolides in a species possessing the mutations for resistance.

New Salamanders of the Genus Oedipina (Caudata: Plethodontidae) from Guatemala

Abstract New salamanders of the genus Oedipina are described from the xeric Motagua Valley in eastern Guatemala, the El Trifinio highlands near the Honduras/El Salvador borders, and the Pacific versant of south-central Guatemala. These new species have been previously associated with known species, but possess distinctive foot morphology, different numbers of teeth, and body morphology and inhabit distinctive environments. Resumen Nuevas especies de salamandras del género Oedipina son descritas del árido Valle de la Motagua en el este de Guatemala, de las tierras altas El Trifinio cerca de la frontera de Honduras y El Salvador, y de la vertiente Pacifico de la parte sur-central de Guatemala. Estas nuevas especies han sido asociadas previamente con otras especies, pero poseen un morfología distintiva, número de dientes diferentes, y viven en ambientes distintos.

A new salamander of the genus chiropterotriton (Caudata: Plethodontidae) from the sierra madre oriental of tamaulipas, Mexico

Abstract. A new salamander of the genus Chiropterotriton is described from the Sierra Madre Oriental in southwestern Tamaulipas, Mexico. This genus is widespread in the Sierra Madre Oriental, its range extending from Tamaulipas to northern Oaxaca, and it occurs into central Mexico along the mountains associated with the Transverse Volcanic Axis. The species described herein is one of the northernmost species. Previously a few species of Chiropterotriton have been reported from the mountains of Tamaulipas and adjacent Nuevo León, but this new salamander is easily distinguished by its enlarged nares. It also differs from all congeners by a combination of characters including size, limb length, hand and foot morphology, color pattern, and dental morphology.

Sublethal contaminant exposure alters behavior in a common insect: important implications for trophic transfer.

This study examined the effects of sub-lethal exposure of the ubiquitous pesticide malathion on the behavior of the model orthopteran species, the house cricket (Acheta domesticus). Increasing concentrations of malathion caused male crickets to increase periods of non-directional movement, such as twitching and grooming, directional movement, and to seek out shelter less. These are all behavioral alterations that may increase the crickets chances of being preyed upon, and thus have the potential for serious ecological consequences through trophic transfer. This study also revealed that female crickets appeared to be less affected by malathion than their male conspecifics, indicating a potential sex-bias in both susceptibility and possible predator attack.

Corticosteroid responses of snakes to toxins from toads (bufadienolides) and plants (cardenolides) reflect differences in dietary specializations

Toads are chemically defended by cardiotonic steroids known as bufadienolides. Resistance to the acute effects of bufadienolides in snakes that prey on toads is conferred by target-site insensitivity of the toxins target enzyme, the Na+/K+-ATPase. Previous studies have focused largely on the molecular mechanisms of resistance but have not investigated the physiological mechanisms or consequences of exposure to the toxins. Adrenal enlargement in snakes often is associated with specialization on a diet of toads. These endocrine glands are partly composed of interrenal tissue, which produces the corticosteroids corticosterone and aldosterone. Corticosterone is the main hormone released in response to stress in reptiles, and aldosterone plays an important role in maintaining ion balance through upregulation of Na+/K+-ATPase. We tested the endocrine response of select species of snakes to acute cardiotonic steroid exposure by measuring circulating aldosterone and corticosterone concentrations. We found that Rhabdophis tigrinus, which specializes on a diet of toads, responds with lower corticosterone and higher aldosterone compared to other species that exhibit target-site resistance to the toxins but do not specialize on toads. We also found differences between sexes in R. tigrinus, with males generally responding with higher corticosterone and aldosterone than females. This study provides evidence of physiological adaptations, beyond target-site resistance, associated with tolerance of bufadienolides in a specialized toad-eating snake.

A Fourth Species of Minute Salamander (Thorius: Plethodontidae) from the Sierra Madre del Sur of Guerrero, Mexico

Abstract A new minute salamander of the genus Thorius is described from the western highlands of the Mexican state of Guerrero. Previously, three congeners were known from the central portion of the state. The fourth species we herein describe occurs in the western portion of the Sierra Madre del Sur of Guerrero and is allopatric from nearest congeners by about 80 km. The new species is distinguished from Guerreran congeners by a combination of body size, external morphology, and dentition.