Acoustic mirror effect increases prey detection distance in trawling bats

Many different and phylogenetically distant species of bats forage for insects above water bodies and take insects from and close to the surface; the so-called trawling behaviour. Detection of surface-based prey by echolocation is facilitated by acoustically smooth backgrounds such as water surfaces that reflect sound impinging at an acute angle away from the bat and thereby render a prey object acoustically conspicuous. Previous measurements had shown that the echo amplitude of a target on a smooth surface is higher than that of the same target in mid-air, due to an acoustic mirror effect. In behavioural experiments with three pond bats (Myotis dasycneme), we tested the hypothesis that the maximum distances at which bats can detect prey are larger for prey on smooth surfaces than for the same prey in an airborne situation. We determined the moment of prey detection from a change in echolocation behaviour and measured the detection distance in 3D space from IR-video recordings using stereo-photogrammetry. The bats showed the predicted increase in detection distance for prey on smooth surfaces. The acoustic mirror effect therefore increases search efficiency and contributes to the acoustic advantages encountered by echolocating bats when foraging at low heights above smooth water surfaces. These acoustic advantages may have favoured the repeated evolution of trawling behaviour.     

Leptospirosis risk increases with changes in species composition of rat populations

Rats are major reservoirs of leptospirosis and considered as a main threat to biodiversity. A recent introduction of Rattus rattus to the island of Futuna (Western Polynesia) provided the opportunity to test if a possible change in species composition of rat populations would increase the risk of leptospirosis to humans. We trapped rodents on Wallis and Futuna and assessed Leptospira carriage in 357 rodents (Rattus norvegicus, R. rattus, Rattus exulans, and Mus domesticus) from 2008 to 2012. While Leptospira prevalence in rodents and the composition of rat populations on Futuna fluctuated with rainfall, the biomass of Leptospira-carrying rodents has been continuously rising from 2008 to 2012. Our results suggest that the introduction of R. rattus increases the risk to humans being infected with leptospirosis by rats.     

Visual prey detection by near-infrared cues in a fish

Many animal species are able to perceive light wavelengths beyond those visible to humans. While numerous species are additionally sensitive to short wavelengths (UV), long wavelengths such as the near-infrared spectrum (NIR) are supposed to be unsuitable for visual perception. Here, we experimentally show that under exclusive NIR illumination, the cichlid fish Pelvicachromis taeniatus displays a clear foraging response towards NIR reflecting prey. Additional control experiments without prey indicate that the observed behavior is not a mere response to the NIR environment. These results give first evidence for NIR visual sensitivity in a functional context and thus challenge the current view about NIR perception.     

Predation and aggressiveness in host plant protection: a generalization using ants from the genus Azteca

In studying the ant genus Azteca, a Neotropical group of arboreal species, we aimed to determine the extent to which the ants use predation and/or aggressiveness to protect their host plants from defoliating insects. We compared a territorially dominant, carton-nester, Azteca chartifex, and three plant-ant species. Azteca alfari and Azteca ovaticeps are associated with the myrmecophyte Cecropia (Cecropiaceae) and their colonies shelter in its hollow branches; whereas Azteca bequaerti is associated with Tococa guianensis (Melastomataceae) and its colonies shelter in leaf pouches situated at the base of the laminas. Whereas A. bequaerti workers react to the vibrations transmitted by the lamina when an alien insect lands on a leaf making it unnecessary for them to patrol their plant, the workers of the three other species rather discover prey by contact. The workers of all four species use a predatory behaviour involving spread-eagling alien insects after recruiting nestmates at short range, and, in some cases, at long range. Because A. alfari and A. ovaticeps discard part of the insects they kill, we deduced that the workers' predatory behaviour and territorial aggressiveness combine in the biotic defence of their host tree.     

A review of postfeeding larval dispersal in blowflies: implications for forensic entomology

Immature and adult stages of blowflies are one of the primary invertebrate consumers of decomposing animal organic matter. When the food supply is consumed or when the larvae complete their development and migrate prior to the total removal of the larval substrate, they disperse to find adequate places for pupation, a process known as postfeeding larval dispersal. Several important ecological and physiological aspects of this process were studied since the work by Green (Ann Appl Biol 38:475, 1951) 50 years ago. An understanding of postfeeding larval dispersal can be useful for determining the postmortem interval (PMI) of human cadavers in legal medicine, particularly because this interval may be underestimated if older dispersing larvae or those that disperse longer, faster, and deeper are not taken into account. In this article, we review the process of postfeeding larval dispersal and its implications for legal medicine, in particular showing that aspects such as burial behavior and competition among species of blowflies can influence this process and consequently, the estimation of PMI.     

Supercooling ability in the house spider, Achaearanea tepidariorum: effect of field-collected and laboratory-reared prey

The influence of prey animals on the supercooling ability of the house spider, Achaearanea tepidariorum, was studied by feeding spiders with field-collected and laboratory-cultured prey animals. Irrespective of the prey species supplied, spiders given field-collected prey had a higher supercooling point than those given laboratory-cultured counterparts. This means that (1) the field prey animals contained some efficient ice nucleators, whereas the laboratory animals were free from such substances and (2) the ice nucleators must be of external origin. Several lines of evidence also suggest that, under natural conditions, potential prey animals for the house spider are highly contaminated with ice nucleators.     

Long-distance island hopping without dispersal stages: transportation across major zoogeographic barriers in a Southern Ocean isopod

Species integrity is maintained only if recurrent allelic exchange between subpopulations occurs by means of migrating specimens. Predictions of this gene flow on the basis of observed or assumed mobility of marine species have proven to be error-prone. Using one mitochondrial gene and seven microsatellite markers, we studied the genetic structure and gene flow in Septemserolis septemcarinata, a strictly benthic species lacking pelagic larvae and the ability to swim. Suitable shallow-water habitats around three remote islands (South Georgia, Bouvet, and Marion Island) are geographically disjunct, isolated by more than 2,000 km of uninhabitable deep sea (east–west) and also separated by the Polar Front (north–south), which serves as a strong demarcation line in many marine taxa. Although we did find genetic differentiation among the three island populations, our results also revealed that a scenario with recent gene flow explains our data best. A model assuming no gene flow after initial colonization of the islands performs significantly worse. The tests also favor an asymmetric gene flow pattern (west to east ≫ east to west) thus mirroring the directionality of major oceanographic currents in the area. We conclude that rare long-distance dispersal rather than vicariance or human-mediated transport must be responsible for the observed patterns. As a mechanism, we propose passive rafting on floating substrata in the Antarctic Circumpolar Current. The results demonstrate that the effectiveness of a physical barrier is not solely a function of its physical parameters but strongly depends on how organisms interact with their environment.     

From Specialization in Spider Egg Predation to an Original Nesting Mode in a "Primitive" Ant: A New Kind of Lestobiosis

 Mature colonies of Discothyrea oculata were observed nesting in cribellatid spider oothecas where they found both shelter and food although these oothecas, installed in preexisting cavities, were protected with crimped silk. Workers of colonies bred in test tubes during laboratory experiments recuperated the silk from spider oothecas introduced into their foraging area, using their mandibles and forelegs, to operculate and line the test tubes. Also, colonies left the test tubes to shelter in the cribellatid spider oothecas. The term "arachnolesty" is proposed for this new kind of lestobiosis. Received: 20 April 1998 / Accepted in revised form: 16 October 1998     

Benefits and costs of controlling three allergenic alien species under climate change and dispersal scenarios in Central Europe

Climate change is likely to exacerbate the negative effects of invasive alien species (IAS) as it will foster their further spread. This paper analyses the potential socio-economic effects of three emerging IAS (giant ragweed, Ambrosia trifida; annual wormwood, Artemisia annua; and burweed marshelder, Iva xanthiifolia), which are known to cause substantial harm to human health and to have negative effects on agricultural production. The novelty of the study consists in an integrated approach that combines several aspects of IAS research and management. We model the future spread of the study species in Central Europe by the year 2050 under several climate change, management and spread scenarios. The costs and benefits of controlling the expansion of these IAS are based on this forecast. The results show that an early and coordinated response to the spread of these IAS yields substantial net benefits under all scenarios. Under the conditions of moderate climate change (+1.5 °C), discounted net benefits range from €19 to €582 million. Assuming more severe climate change (+2.4 °C), total savings over the full period are projected to add up to €1063 million. These large socio-economic benefits provide compelling evidence that public authorities should act preventively to restrict the spread of these three IAS.     

用欧氏距离系数预报舟山海域赤潮发生指数等级

通过选取1996~2007年72个赤潮发生个例为一组样本,另外选取2004年4~9月之间前后3 d之内都没有赤潮发生的92个个例为另一组样本,对赤潮发生前3 d的气压、温度、相对湿度、风速、风向、降水、日照、云量等要素及某些要素3 d的累积值、以及增温的天数、降压的天数等共30个物理量做t统计量分析,并应用欧氏距离系数进行聚类,依此来判别赤潮发生的可能性。在对2008年舟山12次赤潮进行试报中,结果令人满意。     

Tooth hardness increases with zinc-content in mandibles of young adult leaf-cutter ants

A wide variety of arthropods and members of other phyla have elevated concentrations of Zn, Mn, other heavy metals and halogens in their jaws, leg claws, and other "tools" for interacting with the environment. While measured Zn concentrations reach 25% of dry mass in scorpion stings, concentrations are often lower than this and the enriched structures are not heavily biomineralized like vertebrate teeth and the radula of mollusks. For this reason, the degree to which the inorganic components of these structures modify their mechanical properties is in question. Here we address this problem by measuring hardness during the development of Zn accumulations in ant mandibles. We found that Zn is incorporated into the mandibular teeth of leaf-cutter ants during early adult life, reaching concentrations of about 16% of dry mass. We show that the hardness of the mandibular teeth increases nearly three-fold as the adults age and that hardness correlates with Zn content (r=0.91). We suggest that young adults rarely cut leaves partly because their mandibles are not yet rich in Zn. Zinc enrichment (along with enrichment by other heavy metals and halogens) may play an unrecognized role in the behavioral ecology and evolution of a wide variety of invertebrates.     

长输管道穿越河流的环境影响及对策浅析

由于近年来施工机械及河流穿越技术的不断进步,对于各地区不同的气候和地质条件,各类长输管道穿越河流等特殊地段的施工方式日趋多样化,除工程成本及管线安全性外,也更多的考虑到了工程施工给周边环境带来的不良影响,如何在穿越地段选择合理的施工方式和污染防治措施已成为工程设计阶段的重要关注点,本文主要针对目前中国油气长输管道穿越河流段普遍采用的施工方式进行环境影响分析,并在此基础上提出相应污染防治措施。