Extending the cost-benefit model of thermoregulation: high-temperature environments

The classic cost-benefit model of ectothermic thermoregulation compares energetic costs and benefits, providing a critical framework for understanding this process (Huey and Slatkin 1976 ). It considers the case where environmental temperature (T(e)) is less than the selected temperature of the organism (T(sel)), and it predicts that, to minimize increasing energetic costs of thermoregulation as habitat thermal quality declines, thermoregulatory effort should decrease until the lizard thermoconforms. We extended this model to include the case where T(e) exceeds T(sel), and we redefine costs and benefits in terms of fitness to include effects of body temperature (T(b)) on performance and survival. Our extended model predicts that lizards will increase thermoregulatory effort as habitat thermal quality declines, gaining the fitness benefits of optimal T(b) and maximizing the net benefit of activity. Further, to offset the disproportionately high fitness costs of high T(e) compared with low T(e), we predicted that lizards would thermoregulate more effectively at high values of T(e) than at low ones. We tested our predictions on three sympatric skink species (Carlia rostralis, Carlia rubrigularis, and Carlia storri) in hot savanna woodlands and found that thermoregulatory effort increased as thermal quality declined and that lizards thermoregulated most effectively at high values of T(e).     

An endangered bird calls less when invasive birds are calling

Novel noises can affect various animal behaviours, and changes to vocal behaviour are some of the most documented. The calls of invasive species are an important source of novel noise, yet their effects on native species are poorly understood. We examined the effects of invasive bird calls on the vocal activity of an endangered Australian finch to investigate whether: 1) native finch calling behaviour was affected by novel invasive bird calls, and 2) the calls of the finches overlapped in frequency with those of invasive birds. We exposed a wild population of black‐throated finch southern subspecies Poephila cincta cincta to the vocalisations of two invasive birds, nutmeg mannikins Lonchura punctulata and common mynas Acridotheres tristis, a synthetic ‘pink' noise, and a silent control. To determine whether the amount of black‐throated finch calling differed in response to treatments, we recorded and quantified black‐throated finch vocalisations, and assessed the amount of calling using a generalised linear mixed model followed by pairwise comparisons. We also measured, for both black‐throated finches and the stimulus noises: dominant, minimum and maximum frequency, and assessed the degree of frequency overlap between black‐throated finch calls and stimulus noises. Compared to silent controls, black‐throated finches called less when exposed to common myna calls and pink noise, but not to nutmeg mannikin calls. We also found that pink noise overlapped most in frequency with black‐throated finch calls. Common myna calls also somewhat overlapped the frequency range of black‐throated finch calls, whereas nutmeg mannikin calls overlapped the least. It is possible that masking interference is the mechanism behind the reduction in calling in response to common myna calls and pink noise, but more work is needed to resolve this. Regardless, these results indicate that the calls of invasive species can affect the behaviour of native species, and future research should aim to understand the scope and severity of this issue.     

The impact of cattle grazing regimes on tropical savanna bird assemblages

Globally, agricultural land use is implicated in the decline of avifauna. In rangelands (areas used for livestock grazing), bird community responses to grazing can be complex, species‐specific and scale dependent. A greater understanding of bird responses to grazing will lead to more meaningful management recommendations. We tested the hypothesis that foraging height predicts bird species’ responses to grazing, such that species using lower vegetation strata are most likely to respond to the impacts of livestock grazing. We examined the response of a tropical savanna bird community to four grazing strategies at a long‐term grazing trial in northern Australia. We predicted that ground‐foraging guilds would be more responsive to grazing treatment than foliage‐ or aerial‐foraging guilds. We analysed the bird community assemblage using generalised linear mixed models and examined individual species’ abundance in relation to microhabitat variables. We found that while ground‐foraging guilds were more responsive to grazing treatment, individual species dynamics within a foraging guild could be contradictory. For example, the red‐backed fairy‐wren decreased in abundance with increased grazing and was positively associated with grass and shrub (Carissa ovata) cover, whereas Australian magpies increased in abundance in the most heavily grazed paddocks. In general, the responses of bird species to grazing were more pronounced in guilds that forage closer to the ground, but whether the responses were positive or negative was driven by bird species ecology. Measures examining the responses of individual species are more useful than assemblage measures (such as richness) to describe the impacts of anthropogenic disturbance such as grazing.     

Development of real-time assays for impedance-based detection of microbial double-stranded DNA targets: optimization and data analysis

A real-time, label free assay was developed for microbial detection, utilizing double-stranded DNA targets and employing the next generation of an impedimetric sensor array platform designed by Sharp Laboratories of America (SLA). Real-time curves of the impedimetric signal response were obtained at fixed frequency and voltage for target binding to oligonucleotide probes attached to the sensor array surface. Kinetic parameters of these curves were analyzed by the integrated data analysis package for signal quantification. Non-specific binding presented a major challenge for assay development, and required assay optimization. For this, differences were maximized between binding curve kinetic parameters for probes binding to complementary targets versus non-target controls. Variables manipulated for assay optimization included target concentration, hybridization temperature, buffer concentration, and the use of surfactants. Our results showed that (i) different target-probe combinations required optimization of specific sets of variables; (ii) for each assay condition, the optimum range was relatively narrow, and had to be determined empirically; and (iii) outside of the optimum range, the assay could not distinguish between specific and non-specific binding. For each target-probe combination evaluated, conditions resulting in good separation between specific and non-specific binding signals were established, generating high confidence in the SLA impedimetric dsDNA assay results.     

Thermal biology of reproduction in viviparous skinks,Eulamprus tympanum: why do gravid females bask more?

Summary In some reptiles, gravid females bask more, and/or maintain higher body temperatures than do males or non-gravid females. This phenomenon is usually explained in terms of the female or her offspring benefitting from accelerated embryogenesis and early birth, but the effect of increased basking on gestation period has not been studied. In a laboratory experiment, gestation periods of gravid female skinks (Eulamprus tympanum) decreased with the duration of access to radiant heat. Embryonic development was more rapid in the laboratory than in the field, and there were no apparent adverse effects of this accelerated gestation on females or offspring. Number and mass of offspring, survival rates of embryos, relative clutch mass and female mass before and after parturition were not influenced by the decrease in gestation period caused by increased basking. Females selected similar temperatures in the laboratory and field (32° C), despite the availability of higher temperatures in the laboratory. Thus, gestation in the laboratory was accelerated by spending longer periods at usual basking temperatures, rather than by selecting higher temperatures. In the field, mean and modal body temperatures of active animals were similar in gravid females, males and non-gravid females, but gravid females appear to bask more of the time, even in cloudy weather when other members of the population do not bask. Hence, an apparent similarity in thermal regimes of gravid and non-gravid animals may mask significant underlying differences in thermoregulatory strategies.     

Tissue expression and amino acid sequence of murine UDP-N-acetylglucosamine-2-epimerase/N-acetylmannosamine kinase.

Neuraminic acids are widely expressed as terminal carbohydrates on glycoconjugates and are involved in a variety of biological functions. The key enzyme of N-acetylneuraminic acid synthesis is UDP-N-acetylglucosamine-2-epimerase/N-acetylmannosamine kinase, which catalyses the first two steps of neuraminic acid biosynthesis in the cytosol. In this study we report the complete amino acid sequence of the mouse UDP-N-acetylglucosamine-2-epimerase/N-acetylmannosamine kinase. The ORF of 2166 bp encodes 722 amino acids and a protein with a predicted molecular mass of 79.2 kDa. Northern blot analysis and in situ hybridization revealed that UDP-N-acetylglucosamine-2-epimerase/N-acetylmannosamine kinase is expressed at early stages during development and in all tissues investigated with a maximal expression in the liver.     

Echinococcal cyst of the subcutaneous tissue: a rare case report

Hydatid disease is an endemic zoonosis caused by the cestode Echinococcus granulosus. The most common affected organs are the liver and the lungs. Echinococcal cyst located in the subcutaneous tissue constitutes an extremely rare manifestation of the hydatid disease. Here we present a case report with a cystic mass in the subcutaneous tissue of the left gluteal area, diagnosed as being a hydatid cyst.     

Something different for dinner? Responses of a native Australian predator (the keelback snake) to an invasive prey species (the cane toad)

Predictions from foraging theory suggest that the probability a native predator will incorporate a novel type of prey (such as an invasive species) into its diet depends upon the potential benefits (e.g., nutrient input) vs. costs (e.g., handling time) of ingesting it. Cane toads (Bufo marinus) were introduced to Australia in 1935 and are highly toxic to many frog-eating snakes, thus there was strong selection to delete toads from the diet of these species. What has happened, however, to the feeding responses of an Australian snake species that is able to consume toads without dying? Our field surveys in northeastern Queensland show that, despite their high tolerance to toad toxins (compared to other native snakes), keelbacks (Tropidonophis mairii) feed primarily on native frogs rather than cane toads. This pattern occurs because the snakes show active prey preferences; even under standardized conditions in the laboratory, snakes are more likely to consume frogs than toads. When they are force-fed, snakes frequently regurgitate toads but not frogs. Thus, despite the high availability of the abundant toads, these invasive anurans are largely avoided as prey. This probably occurs because consumption of toads, although not lethal to keelbacks, causes significant sublethal effects and confers little nutritional benefit. Hence, keelback populations are not threatened by toad invasion, but neither do the snakes benefit substantially from the availability of a new type of potential prey.     

Knowing with which eye we see: utrocular discrimination and eye-specific signals in human visual cortex

Neurophysiological and behavioral reports converge to suggest that monocular neurons in the primary visual cortex are biased toward low spatial frequencies, while binocular neurons favor high spatial frequencies. Here we tested this hypothesis with functional magnetic resonance imaging (fMRI). Human participants viewed flickering gratings at one of two spatial frequencies presented to either the left or the right eye, and judged which of the two eyes was being stimulated (utrocular discrimination). Using multivoxel pattern analysis we found that local spatial patterns of signals in primary visual cortex (V1) allowed successful decoding of the eye-of-origin. Decoding was above chance for low but not high spatial frequencies, confirming the presence of a bias reported by animal studies in human visual cortex. Behaviorally, we found that reliable judgment of the eye-of-origin did not depend on spatial frequency. We further analyzed the mean response in visual cortex to our stimuli and revealed a weak difference between left and right eye stimulation. Our results are thus consistent with the interpretation that participants use overall levels of neural activity in visual cortex, perhaps arising due to local luminance differences, to judge the eye-of-origin. Taken together, we show that it is possible to decode eye-specific voxel pattern information in visual cortex but, at least in healthy participants with normal binocular vision, these patterns are unrelated to awareness of which eye is being stimulated.     

Experimental improvements in combining CARD-FISH and flow cytometry for bacterial cell quantification

Flow cytometry and Fluorescence In Situ Hybridization are common methods of identifying and quantifying bacterial cells. The combination of cytometric rapidity and multi-parametric accuracy with the phylogenetic specificity of oligonucleotide FISH probes has been regarded as a powerful and emerging tool in aquatic microbiology. In the present work, tests were carried out on E. coli pure culture and marine bacteria using an in-solution hybridization protocol revealing high efficiency hybridization signal for the first one and a lower for the second one. Other experiments were conducted on natural samples following the established CARD-FISH protocol on filter performed in a closed system, with the aim of improving cell detachment and detection. The hybridized cells were then subsequently re-suspended from the membrane filters by means of an optimized detachment procedure. The cytometric enumeration of hybridized marine bacteria reached 85.7% ± 18.1% of total events. The quality of the cytograms suggests that the procedures described may be applicable to the cytometric quantification of phylogenetic groups within natural microbial communities.