Threat-sensitive generalization of predator recognition by larval amphibians

Despite the importance of acquired predator recognition in mediating predator–prey interactions, we know little about the specific characteristics that prey use to distinguish predators from non-predators. Recent experiments with mammals and fish indicate that some prey lacking innate predator recognition have the ability to display anti-predator responses upon their first encounter with those predators if they are similar to predators that the prey has recently learned to recognize. This phenomenon is referred to as generalization of predator recognition. In this experiment, we documented for the first time that larval amphibians (woodfrog, Rana sylvatica) have the ability to generalize the recognition of known predators to closely related novel predators. Moreover, we demonstrated that this ability is dependent on the level of risk associated with the known predator. When red-bellied newt, Cynops pyrrhogaster (known predator), was paired with simulated low risk, tadpoles displayed fright responses to newts and novel tiger salamanders, Ambystoma tigrinum, but not to novel African clawed frogs, Xenopus laevis. However, when the newt was paired with simulated high risk, tadpoles generalized their responses to both tiger salamanders and African clawed frogs. Larval anurans seem to have a wider generalization frame than other animals.     

Distribution of larval host plants of the fruit piercing moth,Othreis fullonia

Summary The adult fruit piercing moth,Othreis fullonia, a native of the indo-Malaysian region, causes severe damage to fruits grown throughout the tropical and subtropical belt from Africa through Asia and Australia to the Pacific Islands. Plants of the family Menispermaceae and the genusErythrina (Fabaceae) serve as larval hosts but the adult moths prefer Menispermaceae plants for oviposition. In Africa, Asia and Australia, the moth does not lay eggs onErythrina since members of the Menispermaceae are abundant. However in the insular Pacific region, where most islands have few or no species of Menispermaceae, the introduced fruit piercing moth utilizesErythrina as an alternate larval host, and either depletes, endangers or causes the possible extinction of Menispermaceae.     

Assessment of the impacts of municipal solid waste dumps on soils and plants

The study aimed at evaluating the impacts of open municipal solid wastes dumps on soil and vegetation near the main roads linking major cities in Nigeria. We hypothesised that the metals from the wastes exerted substantial impacts at the dump sites which affect the soil and plants. Data were analysed from five dump sites and five control sites. The result revealed that the effects of the heavy metals (HM) were significant and higher at the dump sites where their concentrations were far above the EU, and Canadian environmental quality permissible limits for agricultural soils and vegetation. In contrast with dump sites, a significant relationship (R²?=?0.70; p??Cr?>?Pb at both dump sites and control sites. Further study on the effects of more HM on soil and plant is recommended in the area. Recycling and bio-phytoremediation processes should also be introduced.     

Limits to local adaptation: some impacts of temperature on Nucella emarginata differ among populations,while others do not

Predicting future impacts of temperature change require consideration of multiple impacts of temperature on organisms from different populations. We explored the impacts of temperature on feeding, growth, and mortality of emarginated dogwhelks, Nucella emarginata, from three populations (34.459, ?120.473; 34.435, ?119.930; 34.355, ?119.441) that are separated by a total distance of <100 km. Collections and experiments took place September–December 2012. Populations differed both in the number of mussels consumed at 16 and 20 °C and in the difference in feeding at these temperatures. Despite differences in feeding, increases in whelk mortality with temperature did not differ among populations, and in the 16 °C treatment changes in whelk mass did not differ among populations. These results indicate population-specific responses may differ even among geographically close populations. However, some traits may be more adaptable than others and impacts of a given change may be limited by various constraints (e.g., changes in feeding may accompany changes in metabolic needs). Improving our predictions of climate change impacts will require considering these issues, which may be especially important for marine communities where species differ widely in developmental mode, population connectivity, and other traits which may affect responses to changing temperatures.     

Ancient behaviors of larval amphibians in response to an emerging fungal pathogen, <Emphasis Type="Italic">Batrachochytrium dendrobatidis</Emphasis>

Behaviors have evolved in response to various selection pressures over evolutionary time. However, not all behaviors are adaptive. Some presumably “ancient” behaviors, persistent for millions of years, may be detrimental in the face of novel selection pressures in modern times. These pressures include a multitude of emerging infectious diseases which may be stimulated by environmental changes. We examined how a globally emerging amphibian pathogen, Batrachochytrium dendrobatidis (BD), affected two key evolutionarily persistent behaviors displayed by amphibian larvae: aggregation and thermoregulation. Larval aggregation behavior is often essential for foraging, thermoregulation, and antipredator defense, but varies among species. Thermoregulatory behavior speeds larval development in ephemeral habitats. Specifically, we examined whether aggregation and thermoregulatory behaviors changed when exposed to the BD pathogen in two species (Bufo boreas and Rana cascadae) whose larvae aggregate in nature. In laboratory choice tests, larvae of neither species avoided infected conspecifics. BD-exposed B. boreas larvae aggregated, while unexposed R. cascadae larvae associated more frequently with BD-exposed conspecifics. There was no evidence of behavioral fever or altered thermoregulation in larvae of four species we examined (Pseudacris regilla, Rana aurora, B. boreas, R. cascadae). The absence of behavioral fever may suggest an inability of the larvae of some host species to mediate infection risk by this pathogen. Thermoregulatory behaviors may exhibit a high degree of evolutionary inertia in amphibian hosts because they are linked with host physiology and developmental rates, while altered aggregation behaviors could potentially elevate pathogen transmission rates, leading to increased infection risk in social amphibian species.     

Anthropogenic impacts on sedimentation in Jiaozhou Bay,China

In the last 150 years, China transformed its economy from a feudal system (pre-1911) to a modern market economy. During this time, policy-driven rapid development created a series of ecological and environmental problems, especially in the coastal economic regions. Although the synthetic effects are certainly identifiable, the specific effects of different policies in different developing periods have been difficult to disentangle. Here we show that the footprints of Chinese policies in the last 150 years, and their different influences on coastal environments, were archived in the temporal dynamics of sedimentation in Jiaozhou Bay. Before 1935, natural processes predominantly controlled the sedimentation in Jiaozhou Bay. After the introduction of modern economic policies in 1935, the sediment mass accumulation rate (MAR) was overwhelmingly driven by the sea areas of the bay as a result of policy-driven anthropogenic activities (i.e. saltern development, mariculture, and land reclamation). An increasing MAR at the early stage of each policy, followed by a decrease at the late stage was observed. Land reclamation in the 1990s led to a much quicker increase of MAR than the earlier saltern development. Our results demonstrated that marine exploitation, instead of natural processes, are currently regulating the ecological environments of Chinese bays.     

Effect of temperature on the escape responses of larval herring,Clupea harengus

Herring (Clupea harengus L.) larvae from spring and autumn spawning stocks were reared at different constant temperatures from 5° to 17 °C. At equivalent developmental stages, the spring larvae were longer than the autumn larvae and the larvae reared at low temperatures were longer than those reared at high temperatures. At hatching and at the end of the yolk-sac stage, the larvae were induced, by a probe, to make C-start escape responses, which were recorded and analysed using a high-speed video recording at 400 frames s^-1. The response was rapid and of short duration. The tailbeat frequency and swimming speed were measured during the burst of swimming following the C-start at different test temperatures and in larvae with different temperature histories. The tail-beat frequency was strongly temperature-dependent, rising from 19 Hz at 5 °C to 37 Hz at 17 °C with no effect of temperature history, season or developmental stage. The burst-swimming speed ranged at hatching from 75 to 90 mm s^-1 at 5 °C to 110 to 160 mm s^-1 at 17 °C and at yolk resorption from 90–115 mm s^-1 at 5 °C to 175–190 mm s^-1 at 17 °C. The longer, spring-spawned larvae swam faster than the shorter autumn-spawned larvae. When the swimming speeds were expressed as body lengths (L) s^-1, these differences disappeared. Larvae swam from 7–9 L s^-1 at 5 °C to 15–20 L s^-1 at 17 °C at hatching, and from 8–9 L s^-1 at 5 °C to 15–17 L s^-1 at 17 °C at yolk resorption. There was, however, a significantly faster specific swimming speed by the larvae reared at 12 °C in spring 1991.Honorary Research Fellow of the Scottish Association for Marine ScienceUnfortunately, Karen Fretwell was drowned in an accident on 9 January 1993     

Microbes do not follow the elevational diversity patterns of plants and animals

The elevational gradient in plant and animal diversity is one of the most widely documented patterns in ecology and, although no consensus explanation exists, many hypotheses have been proposed over the past century to explain these patterns. Historically, research on elevational diversity gradients has focused almost exclusively on plant and animal taxa. As a result, we do not know whether microbes exhibit elevational gradients in diversity that parallel those observed for macroscopic taxa. This represents a key knowledge gap in ecology, especially given the ubiquity, abundance, and functional importance of microbes. Here we show that, across a montane elevational gradient in eastern Peru, bacteria living in three distinct habitats (organic soil, mineral soil, and leaf surfaces) exhibit no significant elevational gradient in diversity (r2<0.17, P>0.1 in all cases), in direct contrast to the significant diversity changes observed for plant and animal taxa across the same montane gradient (r2>0.75, P<0.001 in all cases). This finding suggests that the biogeographical patterns exhibited by bacteria are fundamentally different from those of plants and animals, highlighting the need for the development of more inclusive concepts and theories in biogeography to explain these disparities.     

Feeding,conversion efficiencies,and growth of larval mummichogs,Fundulus heteroclitus

Feeding rates, conversion efficiencies and growth of larvae of the mummichog Fundulus heteroclitus, an extremely abundant estuarine fish, were measured at temperatures ranging from 18° to 30°C. The food used was Artemia salina nauplii. At the time of total yolk sac absorption (5 to 7 days after hatching), the feeding rate decreased for a short time, an indication of a shift in metabolism. Higher feeding rates and growth occurred at higher rearing temperatures. The highest conversion efficiency (gross growth efficiency) was 1.1%, at 22°C. Mummichog larvae may be energetically inefficient compared with other fish species, but efficiency might not be critical for this fish, which is an opportunistic omnivore in an energy-rich environment.Contribution No. 291 of the Belle W. Baruch Institute for Marine Biology and Coastal Research, supported by DOE contract No. EY-76-5-09-0869.     

平原河网地区滨岸带外来植物入侵现状及影响研究——以上海青浦区为例

河流滨岸带作为一种典型的开放系统,在受到外界干扰的条件下极易被外来植物所入侵并受到严重影响。以上海青浦区为例,通过对河流滨岸带生态系统入侵植物分布及现状调查,以及对两种入侵植物：白花三叶草（Trifolium repens）和加拿大一枝黄花（Solidago canadensis）群落的物种多样性及其土壤特性的实证研究,探讨外来植物入侵对河流滨岸带生态系统造成的影响。结果表明：目前该地区河流滨岸带外来入侵植物共有14科24种,其科、种数分别占到该生态系统所有植物的48．3％与26．1％。入侵植物白花三叶草与加拿大一枝黄花在春、秋两季均显著降低了河流滨岸带植物群落的物种多样性。此外,两种人侵植物也对当地河流滨岸及土壤特性造成了不同程度的影响,其中对土壤含水量、pH值的影响最为显著。该研究填补了平原河网地区河流滨岸带生态系统外来植物入侵研究的空白,有助于今后开展对该生态系统的评价、恢复及管理工作。     

Influence of food concentration,temperature and salinity on the larval development ofBalanus amphitrite

Influence of food concentration (0.5, 1 and 2 x 10⁵ cell ml^–1 ofSkeletonema costatum), temperature (20 and 30°C) and salinity (15, 25 and 35) on the larval development ofBalanus amphitrite (Cirripedia: Thoracica) was examined. The mortality rate at 20°C was lower than at 30°C in general. Increase in food concentration from 0.5 to 1 x 105 cells ml^–1 improved the survival rate, but this was not evident when food concentration was increased to 2 x 105 cells ml^–1. The results indicate that food availability and temperature jointly determine the energy allocation for metamorphic progress. It was observed that the influence of the tested variables varied with instar. At 20 °C the mean duration of the second instar exceeded 3 d and was much longer than other instar durations. The fourth, fifth and sixth instars and the total naupliar period showed that the effect of different salinities at given food concentrations was negligible at 20°C, while at 30°C there was a marked decrease in duration with increasing salinity.     

Impacts of road deicing salt on the demography of vernal pool-breeding amphibians.

Deicing agents, primarily road salt, are applied to roads in 26 states in the United States and in a number of European countries, yet the scale of impacts of road salt on aquatic organisms remains largely under-studied. The issue is germane to amphibian conservation because both adult and larval amphibians are known to be particularly sensitive to changes in their osmolar environments. In this study, we combined survey, experimental, and demographic modeling approaches to evaluate the possible effects of road salt on two common vernal-pond-breeding amphibian species, the spotted salamander (Ambystoma maculatum) and the wood frog (Rana sylvatica). We found that in the Adirondack Mountain Region of New York (USA), road salt traveled up to 172 m from the highway into wetlands. Surveys showed that egg mass densities of spotted salamanders (A. maculatum) and wood frogs (R. sylvatica) were two times higher in forest pools than roadside pools, but this pattern was better explained by road proximity than by increased salinity. Experiments demonstrated that embryonic and larval survival were reduced at moderate (500 muS) and high conductivities (3000 muS) in A. maculatum and at high conductivities in R. sylvatica. Demographic models suggest that such egg and larval stage effects of salt may have important impacts on populations near roads, particularly in the case of A. maculatum, for which salt exposure may lead to local extinction. For both species, the effect of road salt was dependent upon the strength of larval density dependence and declined rapidly with distance from the roadside, with the greatest negative effects being limited to within 50 m. Based on this evidence, we argue that efforts to protect local populations of A. maculatum and R. sylvatica in roadside wetlands should, in part, be aimed at reducing application of road salt near wetlands with high conductivity levels.     

Toxic impact of nanomaterials on microbes,plants and animals

Nanotechnology has many potential applications in medical, agriculture, electronic and sports industries. Nonetheless, there is actually little knowledge on toxic effects of nanomaterial. Here we review nanotoxicity, action mechanisms and fate of nanomaterials. We discuss the impact of nanotoxicity on microbes, plant, animal and human health, and factors like size, shape, surface charge, composition, ionic concentration and physiological. We explain the detection of nanotoxicity at cell and genome levels. Toxicities of commercial nanomaterials, risk management, rules and regulations regarding marketed nanoproducts are also summarized.     

Spectral tuning and perceptual differences do not explain the rejection of brood parasitic eggs by American robins (Turdus migratorius)

By laying their eggs in the nests of other birds, avian brood parasites impose the cost of rearing young upon their hosts. The recognition and rejection of foreign eggs are primary host defenses against costly brood parasitism. Hosts of parasitic brown-headed cowbirds (Molothrus ater) challenge coevolutionary theory because most cowbird hosts accept parasitic eggs despite their drastically different appearance from the hosts’ own eggs. American robins (Turdus migratorius) are one of only 10 % of the over 200 potential cowbird host species to robustly reject parasitic eggs, but the mechanisms driving the sensory bases of foreign egg rejection remain elusive. Our research combined avian visual perceptual modeling and behavioral experimentation to investigate chromatic cues eliciting parasitic egg rejection in American robins. We assessed the effects of perceivable background color differences between real host and model parasite eggs, across all four avian photoreceptors, on rates of rejection of model eggs spanning in color across the entire avian spectral sensitivity range, and including immaculate model eggs matching the natural colors of robin and cowbird eggs. The results suggest that egg rejection in robins is driven by the overall perceivable difference in color between own and artificial eggs, and input from all four single-cone avian photoreceptors affects the rejection decision. The results, however, also reveal that when viewed by the avian eye, natural cowbird eggs appear more similar in background color to robin eggs than predicted by the high rejection rate of these parasitic eggs. This suggests that robins respond specifically to parasitism by cowbirds, despite an apparent lack of sensory tuning toward the detection of the background color of cowbird eggs.     

Survival of communally reared larval and juvenile lobsters,Homarus americanus

Survival of individually reared larval and juvenile stage lobsters, Homarus americanus (Milne-Edwards), was significantly higher than in corresponding groups of communally reared individuals. Among communally reared lobsters, the mortality rate was highest in the second-stage larvae and then progressively decreased in the later stages. The relationship between survival and duration of molt period of each life-cycle stage indicates that asynchronous molting in the groups of communally reared lobsters is a contributing factor to the higher mortality rate. The molting and mortality curves of communally held lobsters reared from the first larval to first or second juvenile stage showed best cross correlation at 0- or 1-day time lag. The decreased mortality rate observed in the later larval and juvenile stages appears to have resulted from the establishment of new behavior patterns. Group interactions which are influenced by numerous extrinsic and intrinsic factors lead to higher mortality rate (cannibalism) among communally reared lobsters.     

Inhibition of attachment of larval barnacles,Balanus amphitrite,by bacterial surface films

Films of bacteria on solid substrata can positively or negatively influence the attachment of marine invertebrate larvae. Effects of marine bacteria on the attachment of cypris larvae of the barnacle Balanus amphitrite Darwin were examined in the laboratory. Bacteria, grown to mid-exponential phase and allowed to adsorb irreversibly to polystyrene petri dishes, attached in densities of 10⁷ cells cm^-2. Assays (22h) were used to compare the effects of adsorbed cells of 18 different bacterial species on larval barnacle attachment. Most of the adsorbed bacteria either inhibited or had no effect on larval attachment compared to clean surfaces. Experiments testing the effect of larval age on barnacle attachment were conducted with six species of bacteria and showed that older larvae attached in higher percentages to clean surfaces and that bacterial films generally inhibited larval attaschment. Both the species of bacteria and the in situ age of the adsorbed bacteria affected barnacle attachment response: older films of Deleya (Pseudomonas) marina were more inhibitory. Bacterial extracellular materials may be involved in the inhibitory process.     

Modeling the impacts of calcite precipitation on the epilimnion of an ultraoligotrophic, hard-water lake

A mass-balance model of calcite precipitation was developed to investigate the interactions of the varied processes governing the generation and fate of calcite in lakes. The model was used in conjunction with data to assess the evolution and impact of calcite precipitation for calcareous, ultraoligotrophic Torch Lake, Michigan (USA). This lake is an ideal setting for implementation of a baseline modeling study of calcite precipitation where the physical drivers could be evaluated without being dominated, as in many systems, by biological processes. The model provides a representation of calcite precipitation with particulate surface area changing over time, and demonstrates that it is possible for the change in water clarity to be explained by calcite precipitation employing standard optical models. Using the mass balance model to quantify the roles of the various chemical, biological and physical processes interacting in the lake's epilimnion, it was shown that the seasonal temperature rise and air-water CO₂ exchange drive calcite precipitation much more than primary production for this ultraoligotrophic system.     

Evaluating growth of larval walleye pollock, Theragra chalcogramma, using cell cycle analysis

Cell cycle analysis of muscle cell division rates offers a new and efficient technique to analyze growth of larval fish. Using this approach, growth of larval walleye pollock was estimated by determining cell proliferation rates, reasoning that growth during early life stages is probably attributed to increases in cell number rather than to increases in cell size. Characteristic patterns of brain and muscle cell division rates were produced in larval walleye pollock by manipulating their diet in the laboratory. The fraction of dividing muscle cells and, to a lesser extent, the fraction of dividing brain cells were direct indicators of fast and slow growth. A model was produced to estimate average growth rate from the fraction of dividing muscle cells. We developed a simple method for preparing and storing the muscle tissue that ensures nucleic acid stability for subsequent analyses and permits sampling in the field. We envision that the cell cycle methodology will have on-site applications, presenting an opportunity to attain real-time estimates of larval fish growth at sea. Determining the proportion of first-feeding larvae with a high fraction of dividing muscle cells may yield a means for predicting the proportion of fast-growing fish, i.e., the potential survivors.     

Environmental influences on larval duration,growth and magnitude of settlement of a coral reef fish

The influence of environmental variables on the planktonic growth, pelagic larval duration and settlement magnitude was examined for the coral reef surgeonfish Acanthurus chirurgus. Newly settled fish were collected daily from patch reefs in the San Blas Archipelago, Caribbean Panama for 3.5 years. Environmental influences on growth were examined at three different life history stages: from 0 to 6 days, 7 to 25 days and from 26 to 50 days after hatching. Larval growth was correlated, using multiple regression techniques, with a combination of factors including solar radiation, rainfall, and along-shore winds. Depending on the life history stage, these accounted for 13–38% of the variation in growth rates when all the months were included in the analyses. Correlations between environmental variables and growth also varied among seasons and were stronger in the dry than in the wet season. During the dry season solar radiation, rainfall and along-shore winds described 57%, 86% and 74% of the variability in growth between 0 and 6 days, 7 and 25 days and 26 and 50 days, respectively. During the wet season rainfall, along-shore winds and temperature only described 38% of the variability in early growth and 27% of growth just before settlement. No significant model was found to describe growth 7–25 days after hatching during the wet season. Rainfall, solar radiation and along-shore winds were negatively correlated with growth up to 25 days after hatching but positively correlated as larvae approached settlement at a mean age of 52 days. Over 65% of the variability in pelagic larval duration was accounted for by a regression model that included solar radiation and along-shore winds. When data sets from wet and dry seasons were analysed separately, along-shore winds accounted for 67% of the change in larval duration in the dry season, and solar radiation accounted for 23% of the variation in larval duration in the wet season. Only 22% of the variability in settlement intensity could be described by solar radiation and temperature, when all months of the year were included in the analysis. Solar radiation and rainfall were included in a regression model that accounted for 40% of the variation in numbers of fish settling during the dry season. This study suggests that the levels of solar radiation, along-shore winds and rainfall during the early larval life can have important effects on the growth, larval duration and consequently, the settlement magnitude of marine fishes. Results also highlight the need to account for seasonality and ontogeny in studies of environmental influences.Communicated by G.F. Humphrey, Sydney