Roads as barriers to animal movement in fragmented landscapes

Roads can act as barriers to animal movement through mortality during crossing attempts or behavioral avoidance. This barrier effect has negative demographic and genetic consequences that can ultimately result in local or regional extinction. Here we use radio-telemetry data on three terrestrial vertebrates (eastern massasauga Sistrurus catenatus , eastern box turtle Terrapene carolina and ornate box turtle Terrapene ornata ) to test whether roads acted as barriers to movement. Specifically, we test whether individuals avoided crossing roads by comparing the number of observed crossings with the number of road crossings predicted by randomizations of individual movement paths. All species crossed roads significantly less often than predicted by chance, indicating strong road avoidance. Results of this study showing behavioral avoidance and previous studies on road mortality indicate that roads are strong barriers to these species. High mortality during crossing attempts would select for road avoidance, reducing the number of individuals killed on roads over time but leading to genetically partitioned subpopulations due to a lack of gene flow. In species that are long-lived and late-maturing, negative genetic effects might not be observable over short time-scales, thus placing populations at high risk of extinction because of a failure to detect an incrementally worsening problem. Formulating successful management strategies for many species in decline will require integrating data on road mortality, animal behavior and population genetics in order to understand more clearly the barrier effect of roads.     

中国特有蛇类资源及保护建议

概述了中国54种特有蛇类状况,对香港盲蛇Typhlops lazelli、温泉蛇Thermophis baileyi、莽山烙铁头蛇Zhaoermia mangshanensis和蛇岛蝮Gloydius shedaoensis 4种极危种类进行了初步分析.讨论了中国特有蛇类的受胁现状及因素,提出保护策略和措施,建议建立中国特有珍稀蛇类繁育基地.     

Crystal structure of Natratoxin, a novel snake secreted phospholipaseA2 neurotoxin from Naja atra venom inhibiting A-type K+ currents

Snake secreted phospholipasesA2 (sPLA2s) are widely used as pharmacological tools to investigate their role in diverse pathophysiological processes. Some members of snake venom sPLA2s have been found to block voltage-activated K(+) channels (K(v) channels). However, most studies involved in their effects on ion channels were indirectly performed on motor nerve terminals while few studies were directly done on native neurons. Here, a novel snake sPLA2 peptide neurotoxin, Natratoxin, composed of 119 amino acid residues and purified from Naja atra venom was reported. It was characterized using whole-cell patch-clamp in acutely dissociated rat dorsal root ganglion (DRG) neurons. It was found to effectively inhibit A-type K(+) currents and cause alterations of channel gating characters, such as the shifts of steady-state activation and inactivation curves to hyperpolarization direction and changes of V(1/2) and slope factor. Therefore, Natratoxin was suggested to be a gating modifier of K(v) channel. In addition, this inhibitory effect was found to be independent of its enzymatic activity. These results suggested that the toxin enacted its inhibitory effect by binding to K(v) channel. To further elucidate the structural basis for this electrophysiological phenomenon, we determined the crystal structure of Natratoxin at 2.2 A resolution by molecular replacement method and refined to an R-factor of 0.190. The observed overall fold has a different structural organization from other K(+) channel inhibitors in animal toxins. Compared with other K(v) channel inhibitors, a similar putative functional surface in its C-terminal was revealed to contribute to protein-protein interaction in such a blocking effect. Our results demonstrated that the spatial distribution of key amino acid residues matters most in the recognition of this toxin towards its channel target rather than its type of fold.     

Two aberrant serpent-eagles may be visual mimics of bird-eating raptors

Two independent cases of visual mimicry involving snake-eating eagles as mimics and more powerful bird-eating hawks as models are proposed. One pair of species is formed by the sympatric West African Serpent-eagle Dryotriorchis spectabilis and Cassin's Hawk Eagle Spizaetus africanus (= Aquila africana ), inhabiting the tropical forests of the African Gulf of Guinea. The second case involves the Madagascar Serpent-eagle Eutriorchis astur and the Madagascar Goshawk Accipiter henstii , both sympatric and endemics of forests in Madagascar. Similarity in plumage colour and pattern as well as in body size and proportions are remarkable in both cases. The species mimicry pairs are in both cases not closely related phylogenetically and greatly differ in diet, making it unlikely that common ancestry or shared foraging strategies explain the resemblance in plumage coloration and pattern. Mimicry may have evolved because the mimic serpent-eagles obtain (the following hypotheses are not mutually exclusive): (1) a foraging advantage by deceiving their snake prey as they may not flee from bird-eating raptors such as the models, (2) a lowered predation or harassment by the models or other predators, and/or (3) reduced mobbing by small birds, which tend to avoid bird-eating raptors. Alternatively, the similarities in plumage described here may be the result of random convergence due to constraints in the evolution of plumage colours and patterns in diurnal raptors.     

危型竹叶青蛇伤性DIC的救治

目的：通过比较单纯中医药治疗与抗蛇毒血清及中西医结合救治方法,观察竹叶青蛇伤性DIC患者的疗效。方法：用抗蛇毒血清、立止血及中西医结合的方法。从1996年8月至2002年9月,共收治危型竹叶青蛇伤性DIC患者25例。结果：25例均治愈。结论：抗蛇毒血清的早期应用是有效方法。抗五步蛇毒血清或抗蝮蛇毒血清和立止血合用,可以对竹叶青蛇毒的出血毒素和促凝毒性起较好的中和作用。     

Connecting behaviour and performance: the evolution of biting behaviour and bite performance in bats

Variation in behaviour, performance and ecology are traditionally associated with variation in morphology. A neglected part of this ecomorphological paradigm is the interaction between behaviour and performance, the ability to carry out tasks that impact fitness. Here we investigate the relationship between biting behaviour and performance (bite force) among 20 species of ecologically diverse bats. We studied the patterns of evolution of plasticity in biting behaviour and bite force, and reconstructed ancestral states for behaviour and its plasticity. Both behavioural and performance plasticity exhibited accelerating evolution over time, and periods of rapid evolution coincided with major dietary shifts from insect‐feeding to plant‐feeding. We found a significant, positive correlation between behavioural plasticity and bite force. Bats modulated their performance by changing their biting behaviour to maximize bite force when feeding on hard foods. The ancestor of phyllostomids was likely a generalist characterized by high behavioural plasticity, a condition that also evolved in specialized frugivores and potentially contributed to their diversification.     

An Examination of Scale-Dependent Resource Use by Eastern Hognose Snakes in Southcentral New Hampshire

ABSTRACT The decline of many snake populations is attributable to habitat loss, and knowledge of habitat use is critical to their conservation. Resource characteristics (e.g., relative availability of different habitat types, soils, and slopes) within a landscape are scale-dependent and may not be equal across multiple spatial scales. Thus, it is important to identify the relevant spatial scales at which resource selection occurs. We conducted a radiotelemetry study of eastern hognose snake (Heterodon platirhinos) home range size and resource use at different hierarchical spatial scales. We present the results for 8 snakes radiotracked during a 2-year study at New Boston Air Force Station (NBAFS) in southern New Hampshire, USA, where the species is listed by the state as endangered. Mean home range size (minimum convex polygon) at NBAFS (51.7 ± 14.7 ha) was similar to that reported in other parts of the species’ range. Radiotracked snakes exhibited different patterns of resource use at different spatial scales. At the landscape scale (selection of locations within the landscape), snakes overutilized old-field and forest edge habitats and underutilized forested habitats and wetlands relative to availability. At this scale, snakes also overutilized areas containing sandy loam soils and areas with lower slope (mean slope = 5.2% at snake locations vs. 6.7% at random locations). We failed to detect some of these patterns of resource use at the home range scale (i.e., within the home range). Our ability to detect resource selection by the snakes only at the landscape scale is likely the result of greater heterogeneity in macrohabitat features at the broader landscape scale. From a management perspective, future studies of habitat selection for rare species should include measurement of available habitat at spatial scales larger than the home range. We suggest that the maintenance of open early successional habitats as a component of forested landscapes will be critical for the persistence of eastern hognose snake populations in the northeastern United States.     

Venoms, venomics, antivenomics

Venoms comprise mixtures of peptides and proteins tailored by Natural Selection to act on vital systems of the prey or victim. Here we review our proteomic protocols for uncoiling the composition, immunological profile, and evolution of snake venoms. Our long-term goal is to gain a deep insight of all viperid venom proteomes. Knowledge of the inter- and intraspecies ontogenetic, individual, and geographic venom variability has applied importance for the design of immunization protocols aimed at producing more effective polyspecific antivenoms. A practical consequence of assessing the cross-reactivity of heterologous antivenoms is the possibility of circumventing the restricted availability of species-specific antivenoms in some regions. Further, the high degree of target specificity makes toxins valuable scaffolds for drug development.     

Obligate costs of parental care to offspring: egg brooding-induced hypoxia creates smaller, slower and weaker python offspring

Python egg brooding typifies parental care because it consists of multiple behaviours that provide for multiple developmental needs. For example, tightly coiling around the eggs benefits embryonic water balance, but periodic female postural adjustments improve embryonic gas exchange. Regardless of these postural adjustments, egg brooding creates a hypoxic intra-clutch environment that constrains embryonic metabolism. We further examined this novel and useful parental care model to determine: (1) any fitness-related costs of egg brooding to offspring; (2) whether any long-term costs are alleviated by postural adjustments. We artificially incubated Children's python ( Antaresia childreni ) clutches and modulated oxygen partial pressure ( P O₂) to create three treatments: normoxic (NRM, 20.3 kPa O₂), brooding [BRD, P O₂ profile typical of clutch P O₂ ( P O_2clutch) in maternally brooded clutches, 15.8–19.3 kPa O₂] and low (LOW, predicted P O₂ profile of maternally brooded P O_2clutch if females did not make postural adjustments, 14.4–18.6 kPa O₂). Using various metrics from ∼12 days pre-hatching to 14 days post-hatching, we demonstrated that NRM offspring were larger, faster and stronger than BRD offspring. As only hatchling heart mass differed between BRD and LOW treatments (LOW > BRD), postural adjustments may not alleviate hypoxia-related costs to embryos. Our results demonstrate that parental care may represent a compromise between competing developmental needs and thus entails obligate costs to the offspring.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 414–421.