Helical Nature of the Ciliary Beat of Paramecium multimicronucleatum*

SYNOPSIS. Phase and interference cinemicrographs of cilia of Paramecium multimicronucleatum, immersed 3–24 hours in 1.0% methyl cellulose, revealed that 1) in swimming Paramecium the cilia beat with a traveling helical wave from base to tip rather than with the back and forth movement usually assumed, 2) during ciliary reversal the cilia merely change direction, but continue to beat with a traveling helical wave, and 3) in stationary Paramecium the beat is conicoidal. The traveling wave appears as an undulatory wave about 1 1/4 wave lengths long in both surface and profile views, and therefore must be helical. Envelope of the wave is cylindrical except near the base. Observations were confirmed in media without methyl cellulose by means of high speed cinemicrography, up to 4000 frames/sec. The back and forth movement, as described in all textbooks and monographs, is based mostly on 1) analogy to the abfrontal cilia (cirri) of Mytilus, which do beat with a back and forth movement, and 2) conclusions drawn from fixed preparations which do not represent what actually happens in a living animal. In a stationary Paramecium the envelope of the beat is conicoidal as seen in profile, but probably is a spiral wave, i.e., similar to a helix but increasing in diameter from base to tip. This change in wave form could be caused by the increase in resistance of the water in a stationary organism over one that is moving. Cilia and flagella (also ciliates and flagellates) are usually distinguished on the basis of wave form, but the present observations, together with previous data on flagella, show that such distinctions are untenable.     

Community Structure of Wetland Birds During Spring Migration Through the Rainwater Basin

Abstract: Staging areas and migratory stopovers of wetland birds have the potential to function as geographic bottlenecks; entire populations within a flyway may be affected by the quality and quantity of available wetland habitat at stopover sites. Although approximately 90% of playa wetlands in the Rainwater Basin (RWB) region of south-central Nebraska, USA, have been destroyed, the area still provides essential stopover habitat for >10 million waterfowl each spring. We evaluated community patterns and species associations to assess importance of assembly rules in structuring wetland bird communities during migration and to better facilitate multispecies conservation and management strategies. We surveyed 36–40 playas twice weekly in the RWB and observed approximately 2.6 million individual migratory wetland birds representing 72 species during 3 spring migrations 2002–2004. We evaluated spatial and temporal species co-occurrence patterns of geese, dabbling ducks, diving ducks, and shorebirds using null model analysis. Goose species co-occurrence scores did not differ from random in any year of the study, suggesting that goose species frequently use the same habitats during migration. Co-occurrence patterns among dabbling ducks were not different than expected by chance in any year; however, when we evaluated co-occurrence at a weekly scale, dabbling ducks co-occurred less often than expected during weeks of peak migration (high abundance), indicating that dabbling duck species spatially segregated at high densities. Diving duck co-occurrence patterns did not differ from random in any year, suggesting that diving duck species used the same habitats during migration. Shorebird species co-occurred less often than expected in 2002 and 2004, and during weeks of high shorebird abundance, indicating that shorebird communities were distinctly structured during those times. Most association values among lesser snow geese (Chen caerulescens) and dabbling duck species were positive, indicating dabbling ducks did not avoid wetlands with snow geese, a concern for waterfowl managers. However, we frequently observed snow geese and dabbling ducks using different microhabitats within a wetland, which indicate species associations and co-occurrence patterns may have occurred at a finer spatial scale than we measured. This approach of co-occurrence analysis will allow wildlife managers charged with multispecies management at migration stopover sites to make informed conservation and management decisions based on community structure rather than historic single-species approaches.     

Mist Net Effort Required to Inventory a Forest Bat Species Assemblage

Abstract: Little quantitative information exists about the survey effort necessary to inventory temperate bat species assemblages. We used a bootstrap resampling algorithm to estimate the number of mist net surveys required to capture individuals from 9 species at both study area and site levels using data collected in a forested watershed in northwestern California, USA, during 1996–2000. The mean number of simulated surveys required to capture individual species varied with species' rarity and ranged from 1.5 to 44.9. We retrospectively evaluated strategies to reduce required survey effort by subsampling data from 1996 to 1998 and tested the strategies in the field during 1999 and 2000. Using data from 1996 to 1998, the mean number of simulated surveys required to capture 8 out of 9 species was 26.3, but a 95% probability of capture required >61 surveys. Inventory efficiency, defined as the cumulative proportion of species detected per survey effort, improved for both the study area and individual sites by conducting surveys later in summer. We realized further improvements in study area inventory efficiency by focusing on productive sites. We found that 3 surveys conducted between 1 July and 10 September at each of 4 productive sites in this 10-km² study area resulted in the capture of 8 species annually. Quantitative estimation of the survey effort required to assess bat species occurrence improves the ability to plan and execute reliable, efficient inventories. Results from our study should be useful for planning inventories in nearby geographical areas and similar habitat types; further, the analytical methods we used to assess effort are broadly applicable to other survey methods and taxa.     

Discriminant analysis of Lepidopteran prey characteristics and their effects on the outcome of bird-feeding trials

Discriminant analysis was used to analyse the results of 348 bird-feeding trials conducted from 1982 to 1985 in Leverett, Massachusetts. Four size classes, seven appearance categories, and five larval host types, based on 163 species of moths and butterflies used as prey in two or more trials, were selected as predictor variables to discriminate between prey taken and not taken by birds. Discriminant analysis of individual feeding trials correctly classified 97.5 percent of prey taken or not-taken and ranked the predictor variables according to their relative importance in determining prey acceptability. Characteristics most acceptable to birds were: (1) large size, (2) bark-like appearance, (3) warning colouration, (4) woody generalist, (5) dead-leaf-like appearance, (6) woody specialist, and (7) medium size. Characteristics least acceptable to birds were: (1) small size, (2) mimetic appearance, (3) butterfly appearance, (4) herbaceous specialist food type, (5) black-and-white appearance, (6) extra large size, and (7) overall generalist feeder. A summary of the analyses includes a discriminant function based on lepidopteran characteristics that can be used to predict the prey acceptability of species not used in this study. A multiple regression analysis of prey taken revealed that size alone and larval host type combined with other prey characteristics were the most important variables in determining the selection of prey regardless of their abundance in the trials.     

Reconstructing the Origins and Migrations of Diasporic Populations: The Case of the European Gypsies

The sociohistorical study of Gypsies/Sinti/Roma has been dominated by the "Gypsy-lorist" paradigm. According to this paradigm, these itinerant people belong to a unitary ethnic group of South Asian origin whose cultural practices have been preserved over the centuries. Recently, this perspective has come under criticism for perpetuating the image of Gypsies as an isolate within the wider context of the development of European societies, and, in particular, for placing too much importance on the external origin of Gypsy cultural and linguistic practices. This article attempts to place the available biological anthropological data for Roma origins and population history (from molecular genetic and clinical studies) in the wider ethnohistorical and linguistic context, and assesses their potential impact for an integrationist approach to Gypsy studies. These data suggest that, while the "Gypsy-lorist" paradigm is problematic, Gypsy populations share a common biological origin, a reality that should not be ignored.     

Amoeboflagellate Transformations and the Gibbs-Donnan Ratio*

SYNOPSIS. A number of protozoa may have amoeboid, flagellated, or intergrade forms. At the present time several mechanisms have been proposed for inducing the formation of each of the above forms, but a definite triggering mechanism has not been elucidated. However, some change in the environment precedes the transformation of the cell from one form to another. Jahn (1962) and Czarska (1964), respectively, correlated ciliary reversal and water expulsion vesicle activity with alterations in the ionic environment. In both cases the processes involved are correlated with changes in the Gibbs-Donnan (G-D) relationship rather than direct ratios or molarities. It seems reasonable to assume that additional environmentally induced phenomena may also be based on changes in the relationship. The assumption is here made that an amoeboid cell, possessing the necessary genetic and physiologic potentials, can respond to certain changes in its environment by enflagellation. The following hypothesis is being considered: a change in the environment that increases the relative concentration of associated divalent cations is perhaps one of the main triggers for amoeba-to-flagellate transformations. Thus, in accordance with the G-D theory, this transformation would be expected to occur when a given ionic environment is diluted. In addition, the transformation is discussed in relation to pH, population density, and other environmental parameters that alter the Gibbs-Donnan ratio.