Microsatellite markers for the whelk Buccinum undatum

Five microsatellite loci are described for the commercially exploited marine gastropod, Buccinum undatum. Levels of polymorphism were variable with three to 19 alleles per locus and expected heterozygosities of 0.26–0.94 in 60 individuals of the population from which the loci were isolated. Homozygote excess at two of the loci might be attributable to null alleles, and these loci should not be used in, for example, parentage analysis. Nevertheless, because null allele frequencies can be estimated and their effects partitioned, all are useful markers for studies of population differentiation.     

Mixed-species bird flocks in dipterocarp forest of north-central Burma (Myanmar)

We studied the bird community in deciduous, dipterocarp forest of north-central Burma (Myanmar) during December 1994, March 1996, and January 1997 and 1999. Most members of this community participated in mixed-species flocks. Seventy-three flocks were encountered during our study, containing 52 species. Of these, 25 species occurred in more than 10% of flocks, and were included in our analyses. There were 26 significant correlations among species pairs, 25 of which were positive. Cluster analysis indicated that there were three principal types of flocks: one consisting mostly of small passerines and picids, commonly including Common Wood-Shrike, Small Minivet and White-browed Fantail, among others; a second type consisting mainly of sylviids, e.g. Arctic, Dusky and Radde's Warblers; and a third type which generally centred around Greater and Lesser Necklaced Laughingthrushes. Bird-eating hawks were numerous at these sites, and we witnessed several attacks on flocks during the study. Thus we infer that enhanced protection from predation is an important benefit conferred by flock membership. In contrast, there was little overlap in foraging behaviour among species, suggesting that foraging facilitation is a relatively minor benefit enjoyed by flock members, although we did observe White-browed Fantails and Greater Racket-tailed Drongos kleptoparasitizing other species on occasion.     

Developmental Stage Age Groups and African Population Structure: The Kusasi of the West African Savanna

African population structures based on censuses exhibit a distinctive pattern of distortion. It is often assumed that the cause for this distortion is systematic biases in age estimates by census enumerators and respondents influenced by perceptions of social and biological development. African developmental stage age groups are the cultural codification of such perceptions. I describe developmental stage age groups among the Kusasi of Bawku District in northeast Ghana, and analyze their age and sex structure for a sample of 1,132 individuals from the village of Zorse. I show that differences between men and women reflect differences in biological and social development, and that cultural concepts of developmental stages could influence age estimates to produce the pattern of distortions typical of those found in African population structures based on censuses. This is supported by a comparison of Bawku District population structure based on the Ghana census and an ethnographic sample census in Zorse which eliminated most age estimate biases.     

Transmission and Scanning Electron Microscopy of the Evaginative Budding Process in Heliophrya sp. (Ciliata,Suctoria)1

ABSTRACT. A sessile, tentacle-bearing protozoon, Heliophrya sp. (Suctoria, Ciliata), reproduces asexually by evaginative budding to form a ciliated swarmer, which begins metamorphosis to the adult form within 30 min of its release from the parent cell. Morphological features of embryogenesis were investigated using transmission and scanning electron microscopy and found to correspond, with certain exceptions, to the few previous reports concerning evaginative budding in suctorians. Following invagination of a portion of the pellicle to form an embryonic cavity within the parent cell, numerous kinetosomes, apparently formed de novo, organize into rows which surround the embryonic cavity and eventually develop cilia that project into the cavity. When the cavity is complete, its walls are extruded through an opening in the parent cell surface. Parent cell cytoplasm streams into the incipient swarmer, thus supplying it with at least the minimum requirement of all cytoplasmic organelles. The ciliated swarmer remains attached to its parent cell for several minutes before it detaches. A complete pellicle is formed in both parent and swarmer prior to detachment. The numerous mitochondria underlying the parent cell pellicle in the vicinity of the attachment area suggest that cross wall formation is an energy-dependent process.     

Intranasal Immunization of Mice Against Naegleria fowleri1

ABSTRACT. The purpose of this research was to determine whether mice could be protected from lethal challenge with Naegleria fowleri by prior intranasal exposure to pathogenic and nonpathogenic Naegleria. Mortality ranged from 0 to 100% for mice inoculated intranasally (i.n.) with 5 × 10³ amebae of 13 human isolates of N. fowleri. Mice were immunized and challenged i.n. using live amebae of strains of low, medium, and high virulence. The greatest protection against lethal challenge was afforded by three immunizing doses of 10³ amebae per dose of the strain of medium virulence. Nonpathogenic N. gruberi also was used to immunize mice i.n. against lethal challenge with N. fowleri. Protection was greater following immunization with N. gruberi than it was after immunization with N. fowleri, suggesting that nonpathogenic N. gruberi may be a better immunogen in protecting mice against lethal naeglerial challenge.     

Estimates of Daily Energy Expenditure in Birds: The Time-Energy Budget as an Integrator of Laboratory and Field Studies

SYNOPSIS. Measures of energy expenditure by free-living birdscan provide quantitative testsof a number of ecological theories,regarding such diverse phenomena as foraging strategies, resourcecompetition, or parental investment. Our confidence in thesetests rests heavily on the confidence we have in the estimatedrates of energy expenditure. The most common approach to obtainingsuch estimates is the construction of time-energy budgets, inwhich the durations of ananimal's daily activities are multipliedby the respective energy costs of the activities, and thesecosts are summed. Our knowledge of the energy costs of activities,particularly locomotion, has greatly advanced in recent years,as has the ability to adequately assess thermoregulatory costs.Comparisons between timeenergy budgets and direct measures ofenergy expenditure obtained using doubly labeled water indicatethat time-energy budgets can yield accurate estimates of energyexpenditure. However, this is likely to be achieved only underfairly rigorous conditions in which resting costs, activitycosts, and thermoregulatory costs are all well described.Evidenceis accumulating to suggest that, under some conditions, energyexpenditure by birds reaches a maximum sustainable level, atwhich point it is limited by the physiological capacitiestoingest and assimilate energy. Under these conditions, behavioralresponses to changing physical environments and resource availabilitymay be critical to the maintenance of energy balance.     

The Influence of Carbon Dioxide and Daily Photon-flux Density on Optimal Leaf Nitrogen Concentration and Root: Shoot Ratio

Using a cost-benefit model, the leaf nitrogen concentrationand root : shoot ratio that maximize whole-plant relative growthrate are determined as a function of the above-ground environment(integrated daily photon flux density and the concentrationof carbon dioxide at the site of fixation within the leaf).The major advantage of this approach is that it determines theadaptive significance of leaf physiology by considering thefunctional integration of leaves and roots. The predicted responseto increasing daily photon flux densities is an increase inoptimal leaf N concentration (N_opt) and a concomitant increasein root: shoot ratio. Increased carbon dioxide concentrations,on the other hand, reduce N_opt and only slightly change root:shoot ratio. The observed increase in leaf nitrogen concentrationfound in plants growing at high altitudes (low CO₂ partial pressure)is also predicted. Since these responses to light and CO₂ maximizethe whole-plant relative growth rate, the observed adjustmentsthat plants make to light and carbon dioxide concentration appearto be adaptive. We show that the relationship between photosynthesis and leafnitrogen concentration is complex and depends on the light andCO₂ levels at which photosynthesis is measured. The shape ofthis function is important in determining N_opt and the oppositeresponse of leaf nitrogen to light and carbon dioxide is shownto be the result of the different effects of light and CO₂ onthe photosynthesis-leaf nitrogen curve. Plant growth, photosynthesis, leaf nitrogen, biomass allocation, optimization, carbon dioxide light     

Low Temperature Effects on Early Vegetative Growth, Leaf Gas Exchange and Water Potential of Chilling-sensitive and Chilling-tolerant Crop Species

Two chilling-sensitive (Phaseolus vulgaris L., Zea mays L.)and two chilling-tolerant (Pisum sativum L., Spinacia oleraceaL.) species were raised in growth chambers under warm (28/18°Cday/night cycle) and cool (18/12°C) temperature regimes.Growth analysis techniques were used to evaluate leaf area andbiomass partitioning during early autotrophic growth. Plantsacclimated to both temperatures were measured for leaf gas exchangeand water potential (     

Competition for food between Neotropical vultures in forest

Carcasses were provided at a gallery forest site in Venezuela to compare the feeding methods of four vulture species. Turkey Vultures or Lesser Yellow-headed Vultures were always the first species to arrive. Black Vultures were most likely to arrive at large carcasses or those in open situations and were the only species to form large feeding groups. King Vultures were equally likely to arrive at small or large carcasses. There were marked differences in feeding technique, food selection, rate of feeding and bill morphology between Turkey, Black and King Vultures, and the level of aggression between species was low compared to intra-specific aggression.