Individual Variation in Trophic Egg Production: Evidence for Maternal Manipulation in Response to Resource and Competition Levels

Females of the subsocial shield bug Parastrachia japonensis (Heteroptera: Parastrachiidae) incorporate trophic eggs (nutritive eggs) into their egg mass. Considerable variation occurs among females in trophic egg number and the proportion of an egg mass that is composed of trophic eggs. Because trophic eggs are essential to the development and survival of young, this variation could significantly impact female fitness. We tested the hypothesis that trophic egg abundance is induced by maternal phenotype (weight, body size) and resource exposure. We predicted that resource limitations would cause females to produce fewer fertile eggs and more trophic eggs and that larger and heavier females would produce more of each egg type. Females ovipositing early in the season are exposed to different resource conditions than those that oviposit late. Thus, we compared egg production patterns between these two groups and several other factors related to nesting. No correlation was seen between body size and trophic egg abundance, or, indeed, egg production, overall; however, heavier females produced heavier egg masses. Counter to our prediction, late females, which had greater access to food, produced significantly more total eggs, fewer fertile eggs, and more trophic eggs than early females. A binomial generalized linear model analysis indicated that the factors most correlated with the percentage of an egg mass destined to become trophic eggs were resource abundance, resulting from early or late oviposition, and distance of the nest from the host tree, with closer females producing more trophic eggs. The findings support our hypothesis that resource availability and, to a lesser extent, maternal phenotype affect trophic egg abundance.     

Light-mediated Formation and Patterning of Hydrogels for Cell Culture Applications

Click chemistries have been investigated for use in numerous biomaterials applications, including drug delivery, tissue engineering, and cell culture. In particular, light-mediated click reactions, such as photoinitiated thiol−ene and thiol−yne reactions, afford spatiotemporal control over material properties and allow the design of systems with a high degree of user-directed property control. Fabrication and modification of hydrogel-based biomaterials using the precision afforded by light and the versatility offered by these thiol−X photoclick chemistries are of growing interest, particularly for the culture of cells within well-defined, biomimetic microenvironments. Here, we describe methods for the photoencapsulation of cells and subsequent photopatterning of biochemical cues within hydrogel matrices using versatile and modular building blocks polymerized by a thiol−ene photoclick reaction. Specifically, an approach is presented for constructing hydrogels from allyloxycarbonyl (Alloc)-functionalized peptide crosslinks and pendant peptide moieties and thiol-functionalized poly(ethylene glycol) (PEG) that rapidly polymerize in the presence of lithium acylphosphinate photoinitiator and cytocompatible doses of long wavelength ultraviolet (UV) light. Facile techniques to visualize photopatterning and quantify the concentration of peptides added are described. Additionally, methods are established for encapsulating cells, specifically human mesenchymal stem cells, and determining their viability and activity. While the formation and initial patterning of thiol-alloc hydrogels are shown here, these techniques broadly may be applied to a number of other light and radical-initiated material systems (e.g., thiol-norbornene, thiol-acrylate) to generate patterned substrates.     

Solar radiation and functional traits explain the decline of forest primary productivity along a tropical elevation gradient

One of the major challenges in ecology is to understand how ecosystems respond to changes in environmental conditions, and how taxonomic and functional diversity mediate these changes. In this study, we use a trait‐spectra and individual‐based model, to analyse variation in forest primary productivity along a 3.3 km elevation gradient in the Amazon‐Andes. The model accurately predicted the magnitude and trends in forest productivity with elevation, with solar radiation and plant functional traits (leaf dry mass per area, leaf nitrogen and phosphorus concentration, and wood density) collectively accounting for productivity variation. Remarkably, explicit representation of temperature variation with elevation was not required to achieve accurate predictions of forest productivity, as trait variation driven by species turnover appears to capture the effect of temperature. Our semi‐mechanistic model suggests that spatial variation in traits can potentially be used to estimate spatial variation in productivity at the landscape scale.     

Animal-to-Animal Variation in Fecal Microbial Diversity among Beef Cattle

The intestinal microbiota of beef cattle are important for animal health, food safety, and methane emissions. This full-length sequencing survey of 11,171 16S rRNA genes reveals animal-to-animal variation in communities that cannot be attributed to breed, gender, diet, age, or weather. Beef communities differ from those of dairy. Core bovine taxa are identified.The gastrointestinal tracts (GIT) of beef cattle are colonized by microorganisms that profoundly impact animal physiology, nutrition, health, and productivity (5). The GIT microbiota potentially impact food safety via pathogen shedding (13) by interacting with organisms such as Salmonella and competing for resources in the GIT. Cattle intestinal microbiota also play an important role in methane emissions, with U.S. beef cattle alone contributing an estimated 3.87 million metric tons of methane into the environment each year, both from rumen and large-intestine fermentations (7). Although the bovine fecal microbiota have been well characterized using culture-based methods, these techniques are necessarily limited to characterizing bacteria that can be grown in the laboratory. Culture-independent methods can reveal community members that are recalcitrant to culture. Only a handful of deep-sequencing studies have been done using culture-independent 16S rRNA-based methods (1, 11, 12, 14), all with dairy cattle, which have a fundamentally different diet and metabolism from beef cattle. Despite the potential contributions of the beef cattle GIT microbiota to animal health, food safety, and global warming, these communities remain poorly characterized. With the advent of pyrosequencing technology, researchers now have the tools to characterize these important communities. Pyrosequencing will allow rapid characterization of large-sample data sets (1). However, the taxonomic information generated by rapid sequencing is approximate by necessity (9), and full-length 16S-rRNA sequencing remains the “gold standard” method. Accordingly, we have characterized fecal bacteria from six feedlot cattle by full-length capillary sequence analysis of 11,171 16S rRNA gene clones (Fig. ​(Fig.11).Open in a separate windowFIG. 1.Bacterial diversity of six feedlot beef cattle. Gray bars represent the percentages of all 16S sequences that were assigned to each taxonomy. Colored dots represent the percentages of 16S sequences from each library that were assigned to each taxonomic group. Asterisks indicate unclassified members of the named taxon. Panel A shows the data for the first 99% of all the sequences. Panel B shows the data for the remaining 1% of sequences. Note differences in scales for panels A and B.Rectal grab fecal samples (n = 6) were collected according to institutional animal care guidelines. All animals were female cross-bred MARCIII beef heifers, 6 to 8 months of age, 214 to 241 kg, housed in the same feedlot pen for 2 months prior to fecal collection, and fed the same typical feedlot beef production growing rations consisting of 61.6% corn silage (41.3% dry matter), 15.2% alfalfa hay, 20.9% corn, and 2.3% liquid supplement.Total fecal DNA was isolated from homogenized samples using MoBio UltraClean fecal kit (Carlsbad, CA). PCR was performed using 27F and 1392R primers (11). Amplification consisted of 25 cycles, with an annealing temperature of 55°C. Amplicons from three reactions per sample were pooled (8), cloned using the Invitrogen TOPO TA cloning kit (Carlsbad, CA), and sequenced bidirectionally with M13 primers using an ABI 3700 sequencer (17). Low-quality and chimeric sequences (6) were excluded from further analysis. Distance matrices were compiled from ClustalW alignments (18) in PHYLIP (4). Pairwise estimates of shared richness were calculated using EstimateS, version 8.2 (R. K. Colwell; http://purl.oclc.org/estimates). DOTUR (16) was used to identify operational taxonomic units (OTUs) and to generate rarefaction curves (Fig. ​(Fig.2),2), richness and evenness estimates, and Shannon''s and Simpson''s diversity indices (Table ​(Table1).1). A 97% similarity cutoff and an 85% similarity cutoff for estimating OTUs were used to approximate species and class-level designations (15). Taxonomies were assigned to one member of each OTU using the RDP “classifier” tool (19), and the RDP taxonomic information was used for Fig. ​Fig.11 and ​and3.3. Common bovine taxa were identified based on inclusion in all three U.S. culture-independent studies (this study and references 1 and 11).Open in a separate windowFIG. 2.Rarefaction curves for six feedlot beef cattle. OTUs were assigned at the 85% DNA sequence similarity level. For comparison purposes, all six curves were truncated after 1,321 sequences.Open in a separate windowFIG. 3.Phylum-level distribution of bacterial sequences from six beef feedlot cattle. Asterisks indicate unclassified members of the named taxon.

TABLE 1.

Richness and diversity indices for 6 beef feedlot cattle

Methylene amine substituted arylindenopyrimidines as potent adenosine A2A/A1 antagonists

A novel series of arylindenopyrimidines were identified as A_2A and A₁ receptor antagonists. The series was optimized for in vitro activity by substituting the 8- and 9-positions with methylene amine substituents. The compounds show excellent activity in mouse models of Parkinson’s disease when dosed orally.     

Multiple selection pressures generate adherence to Bergmann's rule in a Neotropical migratory songbird

Aim Bergmann's rule, the tendency for body size to be positively correlated with latitude, is widely accepted but the mechanisms behind the patterns are still debated. Bergmann's originally conceived mechanism was based on heat conservation; other proposed mechanisms invoke phylogeny, migration distance and resource seasonality. With the goal of examining these mechanisms, we quantified morphological variation across the breeding range of a Neotropical migratory songbird, the cerulean warbler (Dendroica cerulea). Location Deciduous forests of eastern North America. Methods We sampled nine cerulean warbler populations, spanning the species’ breeding range. We captured 156 males using targeted playback and model presentation, and included 127 adult males in our analyses of morphological variation. We used an information‐theoretical approach to identify climatic variables associated with geographical variation in body size. Results Cerulean warbler body size adheres to Bergmann's rule: individuals in northern populations are larger than those in southern populations. Variation in body size is best explained by variation in dry and wet‐bulb temperature and actual evapotranspiration. Main conclusions Adherence to Bergmann's rule by the cerulean warbler appears to be linked to thermodynamics (heat conservation in the north, evaporative cooling in the south) and resource seasonality. Multiple selection pressures can interact to generate a single axis of morphological geographical variation, and even subtle fluctuations in climatic variables can exert significant selection pressures. We suggest that the influence of selection pressures on migrants might be enhanced by migratory connectivity, providing further support for the important role played by this phenomenon in the ecology, evolution and population dynamics of migratory songbirds.     

Sperm motility in the presence of boundaries

The fluid dynamics of sperm motility near both rigid and elastic walls is studied using the immersed boundary method. Simulations of both single and interacting organisms are presented. In particular, we find that nearby organisms originally undulating with a 90° phase shift may adjust their relative swimming velocities and phase-lock. Comparisons with previous analytical results are also discussed. The tendency of a near-wall to attract organisms is demonstrated.