Migration from plant to plant: an important factor controlling densities of the epiphytic cladoceran <Emphasis Type="Italic">Alona</Emphasis> (Chydoridae,Anomopoda) on lake vegetation

We investigated seasonal changes in the density of epiphytic cladocerans Alona spp. (Chydoridae, Anomopoda) in two habitats, emergent and submerged aquatic plants, in Lake Suwa, Japan, from April to August 1998 and from April to November 2000. Alona had a density peak in early June on reeds (emergent) and in late June on Potamogeton malaianus (submerged). In summer, Alona density remained low in both habitats. Although density was positively correlated with the abundance of epiphytic algae, the birth rate was constant and no correlation between algal abundance and clutch size was detected. In a field experiment using ropes as an artificial substrate covered with high and low densities of epiphytic algae as food, more Alona attached to the ropes with the high density of algae. These results suggest that Alona may select food-rich habitats and migrate seasonally, and that migration is an important factor in the population dynamics of epiphytic chydorid cladocerans such as Alona. In Lake Suwa, Alona may migrate from the reed zone to the submerged macrophyte zone in June.     

Defining core habitat of local populations of the gray treefrog (Hyla versicolor) based on choice of oviposition site

Concern over amphibian population declines and loss of terrestrial and aquatic habitat have emphasized the need to define habitat requirements for each stage in a species' life history. The realization that pond-breeding amphibians spend most of their lives in the terrestrial environment suggests the need to protect terrestrial as well as aquatic habitat. Many studies on amphibian populations have focused on emigration from breeding sites to define habitat use; however these studies do not typically elucidate terrestrial activities of adults within the breeding season. We measured colonization rates of artificial pools by gray treefrogs (Hyla versicolor) at multiple distances from natural breeding ponds. We found a non-random distribution of egg deposition among distances, with 95% of eggs deposited within 15 m of the breeding pond. Additionally, we found that the time to first colonization of artificial pools increased with respect to distance. Our results indicate that adult gray treefrogs may travel up to 200 m within a breeding season, and that multiple breeding ponds may be considered part of a single population. We suggest that a minimum core terrestrial habitat of 60 m surrounding breeding sites is appropriate for protection of local populations of gray treefrogs.     

Identification of the molecular mechanisms contributing to polarized trafficking in osteoblasts

The directionality of matrix deposition in vivo is governed by the ability of a cell to direct vesicularflow to a specific target site. Osteoblastic cells direct newly synthesized bone matrix proteins toward the bone surface. In this study, we dissect the molecular mechanisms underlying the polarized trafficking of matrix protein in osteoblasts. We demonstrate using TEM, immunocytochemistry, and cDNA analysis, the ability of osteoblastic cells in culture to form tight junction-like structures and report the expression of the tight junction associated proteins occludin and claudins 1-3 in these cells. We identify intercellular contact sites and the leading edge of migratory osteoblasts as major target sites of vesicular trafficking in osteoblasts. Proteins required for this process, rsec6, NSF, VAMP1, and syntaxin 4, as well as the bone matrix protein, osteopontin, localize to these sites. We demonstrate that osteoblasts in vivo possess VAMP1 and, furthermore, report the expression of two VAMP1 splice variants in these cells. In addition, osteoblasts express the NSF attachment protein alpha-SNAP and the t-SNARE SNAP23. Thus, cell-to-cell contact sites and the leading edge of migratory osteoblasts contain a unique complement of proteins required for SNARE mediated membrane fusion.     

Initial effects of a petroleum operation on Amazonian birds: terrestrial insectivores retreat

Impacts of petroleum activities on birds in the Amazonian forest of Yasuní National Park and the Huaorani Territory, Ecuador, were evaluated using data from 32 standardized 1-day surveys of twenty one 2-ha sites, spread out over 90 km, located at four different distances (0, 0.5, 1.5, and 4.5 km) into floristically diverse, primary, terra firme forest (240–320 m elev.), except one that was in 6-year-old secondary forest. Width of deforestation for roads was 25 m. The 263 species, identified via sight, sound, and mist-netting (4 nets) between 5:45 and 13:30 on days without heavy or constant rain, were grouped into 14 foraging guilds. Discriminant Function Analysis achieved complete separation of the 10 surveys adjacent to roads from the 22 surveys > 0.3 km into the forest, based on species richness per guild. Terrestrial insectivores contributed by far the most (76%) to this separation, and were the only guild to show a significant difference in the average number of species registered between the 6-edge sites and the 15 interior sites (Mann–Whitney U = 4, P = 0.001). Machinery noise seems to particularly affect this guild.     

Measurement of cardiac mechanical function in isolated ventricular myocytes from rats and mice by computerized video-based imaging

Isolated adult cardiac ventricular myocytes have been a useful model for cardiovascular research for more than 20 years. With the recent advances in cellular physiology and transgenic techniques, direct measurement of isolated ventricular myocyte mechanics is becoming an increasingly important technique in cardiac physiology that provides fundamental information on excitation-contraction coupling of the heart, either in drug intervention or pathological states. The goal of this article is to describe the isolation of ventricular myocytes from both rats and mice, and the use of real-time beat-to-beat simultaneous recording of both myocyte contraction and intracellular Ca²⁺ transients. Published: December 11, 2001     

The use of ground beetles (Coleoptera: Carabidae) in conservation assessments of exposed riverine sediment habitats in Scotland and northern England

Exposed riverine sediments (ERS) are an important invertebrate habitat. Ground beetle data from pitfall trap surveys of 165 sites in the catchments of the Rivers Carron, Nith, Spey, Tweed and Eden and from 48 sites in the catchments of the Rivers Blyth, Breamish, Coquet, Glen, Pont, South Tyne, Till, Tweed and Tyne were used to produce ERS habitat classifications in Scotland and northern England respectively. Within each habitat type the quality of sites were assessed using indices based on rarity and fidelity values and using species richness as a measure of diversity. Considerable variation in these indices was seen within and between habitat types, showing potential for their use in assessing site quality and for ranking sites within habitats. The use of standardised invertebrate survey and distribution data, together with species assemblage information, for the conservation of invertebrate habitat types as an alternative to the use of selected indicator species, is discussed.     

Recruitment in invertebrates with short-lived larvae: the case of the bryozoan <Emphasis Type="Italic">Disporella hispida</Emphasis> (Fleming)

Temporal and spatial recruitment patterns of the cyclostome bryozoan Disporella hispida were monitored using settlement plates arranged along three benthic communities of an artificial reef at Blanes (NE Spain, NW Mediterranean). At the study site, the species mainly inhabits semi-obscure caves. By studying recruitment over one year I first inferred the larval release period for D. hispida and described its temporal occurrence in the communities and stations studied. Secondly, I attempted to determine whether the predicted restricted dispersal may account for the species' distribution at the study site. To this purpose, I compared the distribution of early recruits (15 days old) with that of adults. I also investigated environmental factors which may affect the extent of larval dispersal, and described the effects of post-recruitment processes occurring over a 4-month period. The brooding period, inferred from the study of early recruitment, was linked to spring-increments and autumn-decrements of water temperatures. Early recruits were distributed non-randomly in the communities and stations studied, being most abundant in the habitats where adults live. Strong hydrodynamic events seemed to modify this pattern, allowing recruitment out of the parental communities, and may hinder settlement. Post-recruitment mortality events were likely to prevent colonisation of habitats where the species do not live. Overall, philopatry and low post-recruitment mortality in the parental communities appeared to be the main mechanisms determining the distribution of D. hispida at the study site. Electronic Publication     

Tunable, monochromatic X-rays: an enabling technology for molecular/cellular imaging and therapy

Pulsed, tunable, monochromatic X-rays hold great potential as a cellular and molecular probe. These beams can be tuned to the binding energy of orbital electrons in atoms, making them extremely useful in diagnostic k-edge imaging and Auger cascade radiotherapy. Their wide tunability makes them ideal for the performance of various techniques as disparate as protein crystallography and three-dimensional, compressionless, monochromatic mammography. Since only the frequency best suited to the task at hand is used, radiation exposure to patients or animals is exceedingly low when compared to standard X-ray techniques.     

Simplicial edge representation of protein structures and alpha contact potential with confidence measure

Protein representation and potential function are two important ingredients for studying protein folding, equilibrium thermodynamics, and sequence design. We introduce a novel geometric representation of protein contact interactions using the edge simplices from the alpha shape of the protein structure. This representation can eliminate implausible neighbors that are not in physical contact, and can avoid spurious contact between two residues when a third residue is between them. We developed statistical alpha contact potential using an odds-ratio model. A studentized bootstrap method was then introduced to assess the 95% confidence intervals for each of the 210 propensity parameters. We found, with confidence, that there is significant long-range propensity (>30 residues apart) for hydrophobic interactions. We tested alpha contact potential for native structure discrimination using several sets of decoy structures, and found that it often performs comparably with atom-based potentials requiring many more parameters. We also show that accurate geometric representation is important, and that alpha contact potential has better performance than potential defined by cutoff distance between geometric centers of side chains. Hierarchical clustering of alpha contact potentials reveals natural grouping of residues. To explore the relationship between shape and physicochemical representations, we tested the minimum alphabet size necessary for native structure discrimination. We found that there is no significant difference in performance of discrimination when alphabet size varies from 7 to 20, if geometry is represented accurately by alpha simplicial edges. This result suggests that the geometry of packing plays an important role, but the specific residue types are often interchangeable.     

Suspensory locomotion of Lagothrix lagothricha and Ateles belzebuth in Yasuní National Park,Ecuador

A comparative field study of the locomotion of woolly monkeys (Lagothrix lagothricha) and spider monkeys (Ateles belzebuth) in undisturbed rainforest of northeastern Ecuador reveals substantial differences in their use of suspensory modes. Ateles performed both more brachiation (by forelimbs and tail, with trunk rotation), and forelimb swing (similar to brachiation, but without trunk rotation) than Lagothrix. In contrast, in Lagothrix 20% of suspensory movement was by pronograde forelimb swing, which resembles forelimb swing except that the body is held in a pronograde orientation due to the tail and/or feet intermittently grasping behind the trailing forelimb. Ateles never exhibited this mode. Both brachiation and forelimb swing by Ateles were more dynamic than in Lagothrix, consisting of higher proportions of full-stride bouts (versus single-step). Both species used smaller supports for suspensory than for quadrupedal locomotion, and Ateles used both smaller and larger supports for suspension than did Lagothrix. Analysis of support inclination shows that both species tended to perform more above-support movement on horizontal supports and more below-support (suspensory) movement from oblique supports. Our attempt to elucidate the aspects of canopy structure that favor suspension suggests the need for additional kinds of observational data, focusing on the "immediate structural context" of positional events.