A comparison of techniques used to study the morphology of final instar larvae of aphid parasitoids (Hymenoptera: Braconidae: Aphidiinae)

Abstract. The morphology of the head sclerites of final instar larvae of aphid parasitoids prepared from cast larval skins and excised heads of whole larvae are compared, using both optical and scanning electron microscopy. Remarkable differences in the apparent shape of head sclerites, particularly mandibles, were found. Some of these differences are probably due to a consistent dorso-ventral flattening of the head during moulting, observed in cast skin preparations, whereas excised heads tend to flatten antero-posteriorly. The importance of these findings for understanding the three-dimensional shape of final instar mandibles and for the study of larval morphology and taxonomy of Hymenoptera is discussed     

The effect of fire and permafrost interactions on soil carbon accumulation in an upland black spruce ecosystem of interior Alaska: implications for post‐thaw carbon loss

High‐latitude regions store large amounts of organic carbon (OC) in active‐layer soils and permafrost, accounting for nearly half of the global belowground OC pool. In the boreal region, recent warming has promoted changes in the fire regime, which may exacerbate rates of permafrost thaw and alter soil OC dynamics in both organic and mineral soil. We examined how interactions between fire and permafrost govern rates of soil OC accumulation in organic horizons, mineral soil of the active layer, and near‐surface permafrost in a black spruce ecosystem of interior Alaska. To estimate OC accumulation rates, we used chronosequence, radiocarbon, and modeling approaches. We also developed a simple model to track long‐term changes in soil OC stocks over past fire cycles and to evaluate the response of OC stocks to future changes in the fire regime. Our chronosequence and radiocarbon data indicate that OC turnover varies with soil depth, with fastest turnover occurring in shallow organic horizons (～60 years) and slowest turnover in near‐surface permafrost (>3000 years). Modeling analysis indicates that OC accumulation in organic horizons was strongly governed by carbon losses via combustion and burial of charred remains in deep organic horizons. OC accumulation in mineral soil was influenced by active layer depth, which determined the proportion of mineral OC in a thawed or frozen state and thus, determined loss rates via decomposition. Our model results suggest that future changes in fire regime will result in substantial reductions in OC stocks, largely from the deep organic horizon. Additional OC losses will result from fire‐induced thawing of near‐surface permafrost. From these findings, we conclude that the vulnerability of deep OC stocks to future warming is closely linked to the sensitivity of permafrost to wildfire disturbance.     

Piping Plover Chick Foraging,Growth, and Survival in the Great Plains

Abstract: We tested the hypothesis that piping plover (Charadrius melodus) habitat quality and chick survival on the Missouri River, USA, were lower on a cold-water reservoir and downstream from a hypolimnetic (cold-water) release dam with diel water fluctuations (Garrison Dam) than downstream from an epilimnetic dam (Gavins Point Dam). Plovers in adjacent alkali wetlands provided an index to the maximum reproductive potential in the region. Chicks gained weight more rapidly in the alkali wetlands than on epilimnetic and hypolimnetic river reaches. Invertebrate numbers and biomass were higher in the wetlands and epilimnetic reach, but chick survival was lower on the epilimnetic reach. Thus, piping plovers adapted to a variety of prey densities, and other factors, likely predation, reduced survival rates in the epilimnetic reach. Temporal and spatial variability in site quality indices suggests the need for a regional management strategy with different strategies at each site. Managers can minimize effects of local fluctuations in resource abundance and predators by ensuring protection of or creating geographically dispersed habitat. (JOURNAL OF WILDLIFE MANAGEMENT 72(3):682–687; 2008)     

Vegetative morphology and trait correlations in 54 species of Commelinaceae

The morphospace of 54 species of Commelinaceae from nine genera was examined with simultaneous attention to constraints, adaptive hypotheses and relatedness. Eleven morphological traits, including leaf length and width, angle between the leaves and internode distances, were measured for each species and analysed by principal components analysis and nested analysis of variance. The results revealed a significant signal of relatedness in vegetative morphology; genus explained 20–50% of the variance in a single trait. The relationships between some traits are consistent with adaptive explanations. The findings are consistent with the prediction that evolution for optimal phyllotaxis should be relaxed as self‐shading decreases, and that light availability governs leaf size and branching patterns. Constraints potentially explain some trait correlations, and support was found for the hypothesis that structural constraints govern leaf size and internode size correlations. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 158 , 257–268.     

Localization of electrical current flow across the chorionated unfertilized egg of the locust,Locusta migratoria.

Summary

Extracellular currents near the surface of the electrically excitable egg of Locusta migratoria have been studied through the combined use of the 2-dimensional vibrating probe and an intracellular microelectrode. Intracellular current injection increased extracellular current densities to levels readily detectable by the vibrating probe, and it has been possible to show that injected current traverses the egg in the posterior end containing the micropylar zone. Extracellular currents could not be detected during the rising, plateau or falling phases of the long duration (>100s) action potential in the egg. Increases in current density during the hyperpolarizing after potential which lasts for 6–10 min after termination of the action potential were also restricted to the posterior end of the egg. The results suggest that the primary region at which current traverses the chorionated egg is near or at the micropylar zone.     

Biophysical Ecology and Heat Exchange in Insects

When used with observations of behavior and physiology of animalsin known microclimates, a biophysical approach is a powerfultool for predicting body temperatures of insects. For ectothermicinsects, solution of the energy budget equation and use of operativetemperature models have been used to determine the range oftemperatures which an insect can exhibit in a given environment.Knowledge of body temperature has allowed predictions of whenimportant behaviors arepossible in the field, thereby directlyrelating biophysical models to fitness parameters of animals.A proper understanding of the physiological mechanism(s) controllingheat exchange is prerequisite to application and interpretationof information obtained using biophysical techniques. For endothermicinsects, physiological regulation of heat exchange forces amore complicated analysis. Evaluation of thoracic heat exchangealone (aside from indicating whether insects are regulatingT_th) is of little utility for either quantifying total heatexchange, or evaluating thermoregulatory mechanisms withoutfurther information. Further studies of biophysics and physiologyof endothermic insects during flight are needed to correct thesedeficiencies. Application of biophysical techniques has allowedpredictions of behavior of flying insects based onprinciplesof heat exchange which cannot be examined directly. Analysesof endothermy of restinghoneybee swarms and hives indicate thatthese "superorganisms" regulate temperature rather preciselyover a remarkable range of environmental temperature using mechanismsequivalent to thoseused by resting endothermic vertebrates.     

Needle biopsy of the kidneys; studies of two cases of lower nephron nephrosis due to toxic solvents

In two cases of "lower nephron nephrosis" or acute renal failure, needle biopsies of the kidney were performed. The first case developed in a 46-year-old woman following inhalation of vapors from an insecticide spray and a cleaning fluid. The second case was due to ingestion of carbon tetrachloride. Histologic study of the human kidney during toxic nephrosis showed changes confined mainly to the epithelium of the proximal tubules, confirmed the diagnosis, and illuminated the clinical course. Needle biopsy of the kidney during acute renal failure did not influence the course of the disease unfavorably. It was easy, and entailed no complications. Needle biopsy of kidneys may prove as informative and valuable as needle biopsies of the liver by aiding in the prognosis as well as in the diagnosis of various renal diseases.     

The chemical composition and flow of the South Winterbourne in Dorset

Weekly observations were made of the South Winterbourne from October 1970 to December 1971. Flow commenced in November 1970 and ceased in July 1971, a maximum flow of 1.51 m³ s^?1 being recorded in January 1971. The chemical composition was not very variable, but nitrate showed a positive correlation with flow.     

Chemistry and biology of the South Winterbourne, Dorset, England

Changes in discharge and chemical composition are related to biological and physical conditions at eight sites on the South Winterbourne from the source to the confluence with the River Frome. The results show a complex pattern of discharge with nitrate peaks at high discharge values. Mean phosphate values varied from 34·2 μg l^?1 (at the source) to 164·6 μg l^?1. The Winterbourne has a rich flora of algae and higher plants of which the annual sequence is influenced by the flow regime and the effects of human interference by cutting and removal of plants and addition of nutrients. The fauna has much in common with permanent chalk streams but temporary flow conditions favour insects having prolonged resting stages or those which are able to colonize quickly from other areas when flow commences. Many non-insect groups particularly snails, are able to withstand relatively long dry periods.