Aquatic Amphibians Research Articles

A new Mastodonsauroid Temnospondyl from the Triassic of Algeria: Implications for the biostratigraphy and palaeoenvironments of the Zarzaïtine Series, northern Sahara

We describe a new species of mastodonsauroid temnospondyl from Algeria, Stanocephalosaurus amenasensis nov. sp., on the basis of two exquisite skulls from a Lagerstätte found in the lowermost formation of the Zarzaïtine Series, Illizi Basin, in the area of “La Reculée”, In Amenas region, Algeria. The new species is characterized by subtriangular nostrils with concave lateral borders; small orbits; postfrontals posteriorly very wide; very elongate parietals; smoothly concave posterior margin of the skull; ovoid anterior palatal vacuities; very posteriorly pointed choanae; oval interpterygoid fenestrae; and a short anterior extension of the cultriform process of the parasphenoid. S. amenasensis is different than the Algerian taxa previously erected by Lehman (1971)–“Parotosaurus lapparenti” and “Wellesaurus bussoni”–which we consider nomina dubia. It enlarges the distribution of the genus in northern Gondwana and supports the Early-Middle Triassic age of the lowermost formation of the Zarzaïtine Series. It also suggests that the local palaeoclimate was very seasonal and these aquatic amphibians died massively in a dewatering sebkha.

Fine-Tuning of Bitter Taste Receptors May Be Key to Animal Survival

One key to animal survival is bitter taste—the better to avoid ingesting potentially harmful poisons or foods. The evolution of bitter taste has been a hot topic amongst evolutionary biologists, and with more and more DNA data available, a rich area of exploration. Now, Behrens et al. (2014) examined the genetic repertoire of bitter taste receptor genes in chickens and frogs, which represent two extremes. Chickens only have three bitter taste receptor genes (Tas2rs), whereas frogs have more than 50 (humans are somewhere in the middle). They studied the different molecular properties of cloned Tas2r genes and measured their responses when exposed to a panel of 46 natural or synthetic bitter compounds. First, they constructed a gene tree for a selection of Tas2r genes of various vertebrate species and showed that all avian genes come from the same three ancestral genes. Frogs were found to have five ancestral genes, indicating that their expanded repertoire was due to later gene duplication events. They showed that all the three chicken Tas2rs are “broadly tuned” for bitter taste, whereas six frog Tas2rs tested are mixed consisting of broadly as well as narrowly tuned receptors. Interestingly, both chicken and frog receptor repertoires responded to about half of the compounds, showing that the tuning range rather than the number of Tas2r genes was a critical factor. In general, individual substances activated different receptors in clearly separated concentration ranges, which may also provide a clue to the role of bitter taste diversity in enhancing the chance of survival. The authors conclude that a low number of functional Tas2r genes found in chickens can be compensated by an increased average tuning width. They speculate that the environmental duality of amphibian life, living on both land and water, may account for the increased Tas2r gene diversity in frogs. In mixed aquatic and terrestrial environments amphibians such as frogs may have encountered a larger number of bitter compounds, causing the evolutionary pressure to provide a larger taste receptor repertoire.

New dinosaur and crocodylomorph material from the Middle Jurassic (Bathonian) Kilmaluag Formation, Skye, Scotland

Synopsis Archosaur specimens collected from the Kilmaluag Formation (Great Estuarine Group) of Cladach a’Ghlinne, Skye are described. These comprise crocodylomorph material; a pubis and group of osteoderms with an associated tooth; a theropod tooth; and a dinosaur limb bone. The material is regionally important as the Skye assemblage is dominated by aquatic amphibians and amphibious reptiles with terrestrial taxa being comparatively rare. The crocodylomorph pubis is referable to an indeterminate mesoeucrocodylian; the osteoderms and associated tooth to an indeterminate neosuchian. The Kilmaluag Formation has now yielded the only associated and articulated terrestrial/freshwater Middle Jurassic crocodylomorphs from the UK thus far. The theropod tooth is referable to an indeterminate theropod, and provides the first body fossil evidence of a small theropod taxon from the Bathonian of the Hebridean Basin. The dinosaur limb bone is regarded conservatively as an indeterminate dinosaur although it does possess possible theropod affinities.

Partitioning the non-consumptive effects of predators on prey with complex life histories.

Non-consumptive effects (NCEs) of predators on prey can be as strong as consumptive effects (CEs) and may be driven by numerous mechanisms, including predator characteristics. Previous work has highlighted the importance of predator characteristics in predicting NCEs, but has not addressed how complex life histories of prey could mediate predator NCEs. We conducted a meta-analysis to compare the effects of predator gape limitation (gape limited or not) and hunting mode (active or sit-and-pursue) on the activity, larval period, and size at metamorphosis of larval aquatic amphibians and invertebrates. Larval prey tended to reduce their activity and require more time to reach metamorphosis in the presence of all predator functional groups, but the responses did not differ from zero. Prey metamorphosed at smaller size in response to non-gape-limited, active predators, but counter to expectations, prey metamorphosed larger when confronted by non-gape-limited, sit-and-pursue predators. These results indicate NCEs on larval prey life history can be strongly influenced by predator functional characteristics. More broadly, our results suggest that understanding predator NCEs would benefit from greater consideration of how prey life history attributes mediate population and community-level outcomes.

Effects of natural flooding and manual trapping on the facilitation of invasive crayfish-native amphibian coexistence in a semi-arid perennial stream

Aquatic amphibians are known to be vulnerable to a myriad of invasive predators. Invasive crayfish are thought to have eliminated native populations of amphibians in some streams in the semi-arid Santa Monica Mountains of southern California. Despite their toxic skin secretions that defend them from native predators, newts are vulnerable to crayfish attacks, and crayfish have been observed attacking adult newts, and eating newt egg masses and larvae. For 15 years, we have observed invasive crayfish and native California newts coexisting in one stream in the Santa Monica Mountains. During that period, we monitored the densities of both crayfish and newt egg mass densities and compared these to annual rainfall totals. After three seasons of below average rainfall, we reduced crayfish numbers by manual trapping. Our long-term data indicated that crayfish did not fare well in years when rainfall is above the historic average. This invasive predator did not evolve with high velocity streams, and observations indicated that southern California storm events washed crayfish downstream, killing many of them. Newts exhibit increased reproduction in years when crayfish numbers were reduced. A comparison with a nearby stream that does not contain crayfish indicated that newt reproduction positively responded to increased rainfall, but that fluctuations were much greater in the stream that contains crayfish. We suggest that rainfall patterns help explain invasive crayfish/newt coexistence and that management for future coexistence may benefit from manual trapping.

Determination of antimicrobial and heavy metal resistance profiles of some bacteria isolated from aquatic amphibian and reptile species

The aim of the present study was to determine the level of antibiotic resistance patterns and distribution of heavy metal resistance of bacterial isolates from aquatic animals (Lissotriton vulgaris, Pelophylax ridibundus, Emys orbicularis, Mauremys rivulata, and Natrix natrix) in Turkey (Kavak Delta). A total of 153 bacteria have been successfully isolated from cloaca and oral samples of the aquatic amphibians and reptilians which were found, namely, Aeromonas sp. (n = 29), Plesiomonas sp. (n = 7), Vibrio sp. (n = 12), Citrobacter sp. (n = 12), Enterobacter sp. (n = 11), Escherichia sp. (n = 22), Klebsiella sp. (n = 22), Edwardsiella sp. (n = 6), Hafnia sp. (n = 1), Proteus sp. (n = 19), Providencia sp. (n = 8), and Pseudomonas sp. (n = 4). In terms of antibiotic and heavy metal susceptibility testing, each isolate was tested against 12 antibiotics and 4 metals. There was a high incidence of resistance to cefoxitin (46.40 %), ampicillin (44.44 %), erythromycin (35.29 %), and a low incidence of resistance to gentamicin (6.53 %), kanamycin (8.49 %), chloramphenicol (9.15 %), and cefotaxime (10.45 %). The multiple antibiotic resistance index of each bacterial species indicated that bacteria from raised amphibians and reptiles have been exposed to tested antibiotics, with results ranging from 0 to 0.58. Most isolates showed tolerance to different concentrations of heavy metals, and minimal inhibition concentrations ranged from100 to >3,200 μg/mL. According to these results, a significant occurrence of bacteria in the internal organs of reptiles and amphibians, with a high incidence of resistance against antibiotics and heavy metals, may risk aquatic animals and the public health. These data appoint the importance of epidemiological surveillance and microbiological monitoring and reinforce the need to implement environment protection programs for amphibian and reptile species.

The Density Management and Riparian Buffer Study: A large-scale silviculture experiment informing riparian management in the Pacific Northwest, USA

The advent of the Northwest Forest Plan (NWFP) in the early 1990s signaled a new paradigm for management of 9.9millionha of federal forest lands in western Washington and Oregon, USA. The emphasis shifted from commodity timber production to ensuring sustained ecological functioning to meet a broad array of ecosystem services including economic benefits. Under interim guidelines of the NWFP, approximately 1.1millionha are allocated to riparian reserves intended to conserve the ecological functions and processes required to create and maintain habitat for aquatic and riparian-dependent organisms. The Density Management and Riparian Buffer Study (DMS), an operational-scale management experiment, has evaluated the effectiveness of alternative buffer widths in meeting ecological objectives for riparian areas in headwater forests subjected to spatially heterogeneous thinning. Observations in unthinned stream-reaches revealed spatial structuring of amphibian and invertebrate species assemblages in relation to headwater habitats. Riparian buffers defined by the transition between distinct riparian habitat features and upslope forest were sufficient to moderate the effect of thinning on near-stream microclimates and wetted streambed temperatures. These same variable-width buffers were less effective when adjacent to 0.4-ha patch openings. Thinning had little impact on the abundance of aquatic amphibians and there was no evidence of species loss. Results of the study are being used to devise headwater forest management and species conservation strategies, and to improve monitoring methods and watershed assessment tools.

Pulmonary and cutaneous O2gas exchange: a student laboratory exercise in the frog

Gas exchange in animals is ultimately diffusion based, generally occurring across dedicated respiratory organs. In many aquatic amphibians, however, multiple modes of gas exchange exist, allowing for the partitioning of O2 uptake and CO2 excretion between respiratory organs with different efficiencies. For example, due to the physical properties of O2 being vastly different between air and water phases, the lung and skin play disproportionately important roles in O2 uptake. Many aquatic frogs are renowned for their cutaneous gas exchange capacity, where often the majority of CO2 is excreted across the skin. Furthermore, the roles of these gas exchange organs change with the animal's behavior. Under diving conditions, most of the frog's gas exchange needs must be met by the skin. In this article, we describe an interactive undergraduate laboratory that allows a class of students to share equipment while assessing pulmonary and cutaneous respiration in frogs provided with an air/water choice and under enforced dive conditions. Concepts explored in this laboratory exercise include animal energetics, diving reflex, pulmonary and cutaneous gas exchange processes, diffusion-based gas flux, and O2 debt.

Global diversity patterns and cross‐taxa convergence in freshwater systems

Whereas global patterns and predictors of species diversity are well known for numerous terrestrial taxa, our understanding of freshwater diversity patterns and their predictors is much more limited. Here, we examine spatial concordance in global diversity patterns for five freshwater taxa (i.e. aquatic mammals, aquatic birds, fishes, crayfish and aquatic amphibians) and investigate the environmental factors driving these patterns at the river drainage basin grain. We find that species richness and endemism patterns are significantly correlated among taxa. We also show that cross-taxon congruence patterns are often induced by common responses of taxa to their contemporary and historical environments (i.e. convergent patterns). Apart from some taxa distinctiveness (i.e. fishes), the 'climate/productivity' hypothesis is found to explain the greatest variance in species richness and endemism patterns, followed by factors related to the 'history/dispersion' and 'area/environmental heterogeneity' hypotheses. As aquatic amphibians display the highest levels of congruency with other taxa, this taxon appears to be a good 'surrogate' candidate for developing global freshwater conservation planning at the river drainage basin grain.

An artificial lateral line system using IPMC sensor arrays

Most fish and aquatic amphibians use the lateral line system, consisting of arrays of hair-like neuromasts, as an important sensory organ for prey/predator detection, communication, and navigation. In this paper a novel bio-inspired artificial lateral line system is proposed for underwater robots and vehicles by exploiting the inherent sensing capability of ionic polymer–metal composites (IPMCs). Analogous to its biological counterpart, the IPMC-based lateral line processes the sensor signals through a neural network. The effectiveness of the proposed lateral line is validated experimentally in the localization of a dipole source (vibrating sphere) underwater. In particular, as a proof of concept, a prototype with body length (BL) of 10 cm, comprising six millimeter-scale IPMC sensors, is constructed and tested. Experimental results have shown that the IPMC-based lateral line can localize the source from 1–2 BLs away, with a maximum localization error of 0.3 cm, when the data for training the neural network are collected from a grid of 2 cm by 2 cm lattices. The effect of the number of sensors on the localization accuracy has also been examined.

Amphibians at risk? Susceptibility of terrestrial amphibian life stages to pesticides

Current pesticide risk assessment does not specifically consider amphibians. Amphibians in the aquatic environment (aquatic life stages or postmetamorphic aquatic amphibians) and terrestrial living juvenile or adult amphibians are assumed to be covered by the risk assessment for aquatic invertebrates and fish, or mammals and birds, respectively. This procedure has been evaluated as being sufficiently protective regarding the acute risk posed by a number of pesticides to aquatic amphibian life stages (eggs, larvae). However, it is unknown whether the exposure and sensitivity of terrestrial living amphibians are comparable to mammalian and avian exposure and sensitivity. We reviewed the literature on dermal pesticide absorption and toxicity studies for terrestrial life stages of amphibians, focusing on the dermal exposure pathway, that is, through treated soil or direct overspray. In vitro studies demonstrated that cutaneous absorption of chemicals is significant and that chemical percutaneous passage, P (cm/h), is higher in amphibians than in mammals. In vivo, the rapid and substantial uptake of the herbicide atrazine from treated soil by toads (Bufo americanus) has been described. Severe toxic effects on various amphibian species have been reported for field-relevant application rates of different pesticides. In general, exposure and toxicity studies for terrestrial amphibian life stages are scarce, and the reported data indicate the need for further research, especially in light of the global amphibian decline.

Estimating vertebrate, benthic macroinvertebrate, and diatom taxa richness in raftable Pacific Northwest rivers for bioassessment purposes

The number of sites sampled must be considered when determining the effort necessary for adequately assessing taxa richness in an ecosystem for bioassessment purposes; however, there have been few studies concerning the number of sites necessary for bioassessment of large rivers. We evaluated the effect of sample size (i.e., number of sites) necessary to collect vertebrate (fish and aquatic amphibians), macroinvertebrate, and diatom taxa from seven large rivers in Oregon and Washington, USA during the summers of 2006-2008. We used Monte Carlo simulation to determine the number of sites needed to collect 90-95% of the taxa 75-95% of the time from 20 randomly located sites on each river. The river wetted widths varied from 27.8 to 126.0m, mean substrate size varied from 1 to 10cm, and mainstem distances sampled varied from 87 to 254km. We sampled vertebrates at each site (i.e., 50 times the mean wetted channel width) by nearshore-raft electrofishing. We sampled benthic macroinvertebrates nearshore through the use of a 500-μm mesh kick net at 11 systematic stations. From each site composite sample, we identified a target of 500 macroinvertebrate individuals to the lowest possible taxon, usually genus. We sampled benthic diatoms nearshore at the same 11 stations from a 12-cm(2) area. At each station, we sucked diatoms from soft substrate into a 60-ml syringe or brushed them off a rock and rinsed them with river water into the same jar. We counted a minimum of 600 valves at 1,000× magnification for each site. We collected 120-211 diatom taxa, 98-128 macroinvertebrate taxa, and 14-33 vertebrate species per river. To collect 90-95% of the taxa 75-95% of the time that were collected at 20 sites, it was necessary to sample 11-16 randomly distributed sites for vertebrates, 13-17 sites for macroinvertebrates, and 16-18 sites for diatoms. We conclude that 12-16 randomly distributed sites are needed for cost-efficient sampling of vertebrate richness in the main stems of our study rivers, but 20 sites markedly underestimates the species richness of benthic macroinvertebrates and diatoms in those rivers.

INTRODUCED AQUATIC HERPETOFAUNA OF SINGAPORE'S RESERVOIRS

Sixteen species of introduced or alien aquatic amphibians and reptiles have been recorded from Singapore's Public Utilities Board reservoirs. Their presence in the wild state is largely due to members of the public abandoning their pets, or releasing animals to gain spiritual merit (fang sheng). The ban imposed by the Agri-Food and Veterinary Authority on the sale of most species of amphibians and reptiles will probably help to restrict the diversity of alien animal species in Singapore. However, the continued availability of hatchling red-eared terrapins in pet shops and live Chinese softshell turtles and American bullfrogs in markets does little to reduce the presence of these three alien species in local water bodies.

Functional origins of the vertebrate cerebellum from a sensory processing antecedent

Abstract The structure of the cerebellar cortex is remarkably similar across vertebrate phylogeny. It is well developed in basal jawed fishes, such as sharks and rays with many of the same cell types and organizational features found in other vertebrate groups, including mammals. In particular, the lattice-like organization of cerebellar cortex (with a molecular layer of parallel fibres, interneurons, spiny Purkinje cell dendrites, and climbing fires) is a common defining characteristic. In addition to the cerebellar cortex, fishes and aquatic amphibians have a variety of cerebellum-like structures in the dorso-lateral wall of the hindbrain. These structures are adjacent to, and in part, contiguous with, the cerebellum. They derive their cerebellum-like name from the presence of a molecular layer of parallel fibers and inhibitory interneurons, which has striking organizational similarities to the molecular layer of the cerebellar cortex. However, these structures also have characteristics which differ from the cerebellum. For example, cerebellum-like structures do not have climbing fibres, and they are clearly sensory. They receive direct afferent input from peripheral sensory receptors and relay their outputs to midbrain sensory areas. As a consequence of this close sensory association, and the ability to characterise their signal processing in a behaviourally relevant context, good progress has been made in determining the fundamental processing algorithm in cerebellar-like structures. In particular, we have come to understand the contribution to signal processing made by the molecular layer, which provides an adaptive filter to cancel self-generated noise in electrosensory and lateral line systems. Given the fundamental similarities of the molecular layer across these structures, coupled with evidence that cerebellum-like structures may have been the evolutionary antecedent of the cerebellum, we address the question: do both share the same functional algorithm?

Toxicity of coal-tar pavement sealants and ultraviolet radiation to Ambystoma Maculatum

Polycyclic aromatic hydrocarbons (PAHs) can affect amphibians in lethal and many sublethal ways. There are many natural and anthropogenic sources of PAHs in aquatic environments. One potentially significant source is run off from surfaces of parking lots and roads that are protected with coal tar sealants. Coal tar is 50% or more PAH by wet weight and is used in emulsions to treat these surfaces. Break down of sealants can result in contamination of nearby waters. The toxicity of PAHs can be greatly altered by simultaneous exposure to ultraviolet radiation. This study exposes larvae of the spotted salamander (Ambystoma maculatum) to determine if coal tar sealant can have negative effects on aquatic amphibians and if coal tar toxicity is influenced by ultraviolet radiation. Spotted salamanders were exposed to 0, 60, 280 and 1500 mg coal tar sealant/kg sediment for 28 days. Half of the animals were exposed to conventional fluorescent lighting only and half were exposed to fluorescent lighting plus ultraviolet radiation. No significant mortality occurred during the experiment. Exposure to sealants resulted in slower rates of growth, and diminished ability to swim in a dose-dependent fashion. Exposure to ultraviolet radiation affected the frequencies of leukocytes and increased the incidence of micronucleated erythrocytes. There was an interactive effect of sealant and radiation on swimming behavior. We conclude that coal-tar sealant and ultraviolet radiation increased sublethal effects in salamanders, and may be a risk to salamanders under field conditions.

Development of Biological Diversity in Farmland Ponds

ABSTRACT To describe the rate of pond diversity development and how the age of ponds affects diversity of plants, amphibians, and aquatic insects, eight recently created artificial ponds (four young ponds created in the year 2003 and four new ponds created in the year 2007) were compared to four reference ponds. For each pond, we recorded the presence of plants and the abundance of amphibians and aquatic insects in plots of 0.25 m2 along two orthogonal transects. Data were analyzed using rarefaction technique, permutation tests for multivariate analysis of variance (PERMANOVA), and rank-abundance diagrams. The new and young ponds showed lower plant and aquatic insect species richness than the reference ponds, and the communities showed gradual changes over time in all three taxa Amphibians, which were absent from new ponds, reached the same species richness as in reference ponds five years after pond creation. PERMANOVA wormed on presence/absence data showed no significant differences in community composition for aquatic insects and amphibians among pond age but showed significant differences among ponds belonging to, the same age classes for all taxa studied.

A New Trematopid Amphibian (Temnospondyli: Dissorophoidea) from the Upper Pennsylvanian of Western Pennsylvania: Earliest Record of Terrestrial Vertebrates Responding to a Warmer, Drier Climate

Fedexia striegeli, a new genus and species of trematopid temnospondyl amphibian, is described on the basis of a single specimen that includes the greater portion of the skull and articulated portions of both mandibles and the atlas-axis complex, The holotype was collected from Upper Pennsylvanian—early Virgilian strata assignable to the lower part of the Casselman Formation of the Conemaugh Group in western Pennsylvania. This is not only the first trematopid to be reported from the State of Pennsylvania, but also, in addition to Actiobates Eaton, 1973, and Anconastes Berman et al., 1987, only the third reported Late Pennsylvanian member of the family that otherwise has a greater Early Permian representation.A cladistic analysis of the Dissorophoidea was performed utilizing primarily cranial characters and only members of Amphibamidae, Trematopidae, and Dissorophidae that are well represented in this field of inquiry. This includes Ecolsonia Vaughn, 1969, whose relationships to the latter two families have been controversial. The resultant cladogram depicts: 1) Fedexia to be nested within a monophyletic Trematopidae as the sister taxon to the terminal dichotomy of Anconastes and Tambachia Sumida et al., 1998; 2) Trematopidae and Dissorophidae as forming monophyletic sister clades; and 3) Ecolsonia, Dissorophus Cope, 1895, and Broiliellus Williston, 1914, as forming an unresolved, terminal trichotomy within the dissorophid clade.Fedexia is representative of a wide variety of Late Pennsylvanian, medium-to-large amphibian and amniote tetrapods that record the earliest occurrence of vertebrates adapted to a terrestrial existence in North America. It is hypothesized that this biotic event was in response to the final stage of a long-term, global climatic trend toward drier conditions during the Pennsylvanian from perhumid to humid during the Early and Middle Pennsylvanian to dry subhumid or semiarid in the latest Virgilian. The lattermost climatic stage, which was also coincident with a marked retreat of the southern polar hemisphere glaciers during the late Paleozoic Ice Age, was followed by a strong and progressive reversal of the climate and an advance of the southern hemisphere glaciers to conditions characteristic of the earlier Pennsylvanian.Climatic changes during the Pennsylvanian are chronicled not only by major changes in rock types and associated lithologies, but also by a shift in the biology of the vertebrates they preserve. Middle Pennsylvanian vertebrates are characterized by large, diverse assemblages of predominantly small, aquatic amphibians and fish preserved in black shales and cannel coals associated with coal-forming and sapropelic fluvial sediments that developed in permanently wet, abandoned river channels. In contrast, the terrestrially adapted vertebrates of the Missourian—Virgilian Pennsylvanian are typically preserved in thin deposits of freshwater limestone or their closely associated paleosols that are interpreted as representing seasonally dry lake deposits. Yet, aquatic amphibians continue to be a major constituent of Late Pennsylvanian vertebrate assemblages.

A Predictive Index of Biotic Integrity Model for Aquatic‐Vertebrate Assemblages of Western U.S. Streams

AbstractBecause of natural environmental and faunal differences and scientific perspectives, numerous indices of biological integrity (IBIs) have been developed at local, state, and regional scales in the USA. These multiple IBIs, plus different criteria for judging impairment, hinder rigorous national and multistate assessments. Many IBI metrics are calibrated for water body size, but none are calibrated explicitly for other equally important natural variables such as air temperature, channel gradient, or geology. We developed a predictive aquatic‐vertebrate IBI model using a total of 871 stream sites (including 162 least‐disturbed and 163 most‐disturbed sites) sampled as part of the U.S. Environmental Protection Agency's Environmental Monitoring and Assessment Program survey of 12 conterminous western U.S. states. The selected IBI metrics (calculated from both fish and aquatic amphibians) were vertebrate species richness, benthic native species richness, assemblage tolerance index, proportion of invertivore‐piscivore species, and proportion of lithophilic‐reproducing species. Mean model IBI scores differed significantly between least‐disturbed and most‐disturbed sites as well as among ecoregions. Based on a model IBI impairment criterion of 0.44 (risks of type I and II errors balanced), an estimated 34.7% of stream kilometers in the western USA were deemed impaired, compared with 18% for a set of traditional IBIs. Also, the model IBI usually displayed less variability than the traditional IBIs, presumably because it was better calibrated for natural variability.

Chytridiomycosis in an Aquarium Collection of Frogs: Diagnosis, Treatment, and Control

The introduction of a new group of dendrobatid frogs to an established captive amphibian collection was followed by several acute mortalities in both resident and introduced frog populations. Chytridiomycosis, caused by Batrachochytrium dendrobatidis, was diagnosed by histology in two of the dead frogs. Following the diagnosis, all amphibians were moved to a specially made quarantine room with strict handling protocols and treated with itraconazole. Frogs, being terrestrial amphibians, were treated with itraconazole (Sporanox, 10 mg/ml) at 0.01% in 0.6% saline in a 5-min bath for 11 consecutive days. Axolotls (Ambystoma mexicanum) and Kaup's caecilians (Potymotyphlus kaupii), being aquatic amphibians, were treated with itraconazole administered directly in their primary tank water to achieve a concentration of 0.01% for 30 min every 5 days for four treatments. Itraconazole was removed from the tank water after 30 min by high-rate-of-flow activated charcoal filters. The treatment and quarantine procedures were successful in eradicating the disease. The few amphibian mortalities that occurred in the 18 mo after the start of the treatment have been histologically negative for the presence of chytrid fungi. The collection is now considered free of chytridiomycosis.

Peripheral and central processing of lateral line information

The lateral line is a hydrodynamic sensory system that allows fishes and aquatic amphibians to detect the water motions caused, for instance, by conspecifics, predators or prey. Typically the peripheral lateral line of fishes consists of several hundred neuromasts spread over the head, trunk, and tail fin. Lateral line neuromasts are mechanical low-pass filters that have an operating range from <1 Hz up to about 150 Hz. Within this frequency range, neuromasts encode the duration, local direction, amplitude, frequency, and phase of a hydrodynamic stimulus. This paper reviews the peripheral and central processing of lateral line information in fishes. Special attention is given to the coding of simple and complex hydrodynamic stimuli, to parallel processing, the roles of the various brain areas that process hydrodynamic information and the centrifugal (efferent) control of lateral line information. The review argues that in order to fully comprehend peripheral and central lateral line information processing, it is imperative to do comparative studies that take into account the ecology of fishes, meaning that natural stimulus and noise conditions have to be considered.