Confusion of predators does not rely on specialist coordinated behavior

Antipredatory benefits are generally considered important inthe evolution and maintenance of animal aggregations. One suchbenefit is the confusion effect: the reduced ease of prey captureexperienced by some predators resulting from an inability tosingle out and attack an individual prey from a group as a resultof cognitive or sensory limitations. Although widely cited,empirical data that do any more than demonstrate the effectare sparse. Here, we use the artificial system of humans attemptingto "capture" images on a computer screen using a computer mouseto explore several hypotheses on the properties of the confusioneffect. This system has the advantage that we can control thebehavior of the prey and eliminate the risk of confounding factorsdue to differential prey behavior and/or phenotypes in groupsof different sizes. One important result of our study is thedemonstration that the confusion effect can occur in the absenceof these confounding factors and indeed in the absence of complexcoordinated behavior between individuals in the prey group (suchas are commonly observed in schooling fish). We also demonstratefor the first time that an individual prey item can still benefitfrom the confusion effect if it is only loosely associated inspace with a larger group of similar prey. Both these resultssuggest that the confusion effect can arise under less specialistcircumstances than previously realized, and so the importanceof this mechanism in shaping aggregation by prey and predator–preyinteractions may be substantially greater than previously considered.     

A lifetime at depth: vertical distribution of southern elephant seals in the water column

Although numerous studies have addressed the migration and dive behaviour of southern elephant seals (Mirounga leonina), questions remain about their habitat use in the marine environment. We report on the vertical use of the water column in the species and the potential lifetime implications for southern elephant seals from Marion Island. Long-term mark-resight data were used to complement vertical habitat use for 35 known individuals tagged with satellite-relay data loggers, resulting in cumulative depth use extrapolated for each individual over its estimated lifespan. Seals spent on average 77.59% of their lives diving at sea, 7.06% at the sea surface, and 15.35% hauled out on land. Some segregation was observed in maximum dive depths and depth use between male and female animals—males evidently being physiologically more capable of exploiting increased depths. Females and males spent 86.98 and 80.89% of their lives at sea, respectively. While at sea, all animals spent more time between 300 and 400 m depth, than any other depth category. Males and females spent comparable percentages of their lifetimes below 100 m depth (males: 65.54%; females: 68.92%), though males spent 8.98% of their lives at depths in excess of 700 m, compared to females’ 1.84% at such depths. Adult males often performed benthic dives in excess of 2,000 m, including the deepest known recorded dive of any air-breathing vertebrate (>2,133 m). Our results provide a close approximation of vertical habitat use by southern elephant seals, extrapolated over their lifespans, and we discuss some physiological and developmental implications of their variable depth use.     

Hepatic differentiation of murine embryonic stem cells.

Murine embryonic stem (ES) cells can replicate indefinitely in culture and can give rise to all tissues, including the germline, when reimplanted into a murine blastocyst. ES cells can also be differentiated in vitro into a wide range of cell types. We have utilized a liver-specific marker to demonstrate that murine ES cells can differentiate into hepatocytes in vitro. We have used ES cells carrying a gene trap vector insertion (I.114) into an ankyrin repeat-containing gene (Gtar) that we have previously shown provides an exclusive beta-galactosidase marker for the early differentiation of hepatocytes in vivo. beta-Galactosidase-positive cells were differentiated from I.114 ES cells in vitro. The identity of these cells was confirmed by the expression of the proteins alpha-fetoprotein, albumin, and transferrin and by the fact that they have an ultrastructural appearance consistent with that of embryonic hepatocytes. We propose that this model system of hepatic differentiation in vitro could be used to define factors that are involved in specification of the hepatocyte lineage. In addition, human ES cells have recently been derived and it has been proposed that they may provide a source of differentiated cell types for cell replacement therapies in the treatment of a variety of diseases.     

Individuals from different-looking animal species may group together to confuse shared predators: simulations with artificial neural networks

Individuals of many quite distantly related animal species find each other attractive and stay together for long periods in groups. We present a mechanism for mixed-species grouping in which individuals from different-looking prey species come together because the appearance of the mixed-species group is visually confusing to shared predators. Using an artificial neural network model of retinotopic mapping in predators, we train networks on random projections of single- and mixed-species prey groups and then test the ability of networks to reconstruct individual prey items from mixed-species groups in a retinotopic map. Over the majority of parameter space, cryptic prey items benefit from association with conspicuous prey because this particular visual combination worsens predator targeting of cryptic individuals. However, this benefit is not mutual as conspicuous prey tends to be targeted most poorly when in same-species groups. Many real mixed-species groups show the asymmetry in willingness to initiate and maintain the relationship predicted by our study. The agreement of model predictions with published empirical work, the efficacy of our modelling approach in previous studies, and the taxonomic ubiquity of retinotopic maps indicate that we may have uncovered an important, generic selective agent in the evolution of mixed-species grouping.     

Varietal differences of carbohydrates in defatted soybean flour and soy protein isolate by-products

Soy protein isolates (SPI) were prepared from 12 soybean lines grown in Harrow, Ontario and by-products (fibers and wheys) from SPI making were saved. The identification and quantification of soluble sugars in defatted flours, fibers and wheys were carried out using high-performance anion-exchange chromatography coupled with pulsed amperometric detection (HPAEC-PAD) and with a colorimetric method for uronic acids. Defatted flours and fibers were acid hydrolyzed, then analyzed by HPAEC-PAD for monosaccharide composition. The results showed varietal differences in the carbohydrate composition suggesting different applications for these defatted flours and their SPI by-products.     

GPCR ligand dendrimer (GLiDe) conjugates: adenosine receptor interactions of a series of multivalent xanthine antagonists

Previously, G protein-coupled receptor (GPCR) agonists were tethered from polyamidoamine (PAMAM) dendrimers to provide high receptor affinity and selectivity. Here, we prepared GPCR ligand--dendrimer (GLiDe) conjugates from a potent adenosine receptor (AR) antagonist; such agents are of interest for treating Parkinson's disease, asthma, and other conditions. Xanthine amine congener (XAC) was appended with an alkyne group on an extended C8 substituent for coupling by Cu(I)-catalyzed click chemistry to azide-derivatized G4 (fourth-generation) PAMAM dendrimers to form triazoles. These conjugates also contained triazole-linked PEG groups (8 or 22 moieties per 64 terminal positions) for increasing water-solubility and optionally prosthetic groups for spectroscopic characterization and affinity labeling. Human AR binding affinity increased progressively with the degree of xanthine substitution to reach K(i) values in the nanomolar range. The order of affinity of each conjugate was hA(2A)AR > hA(3)AR > hA(1)AR, while the corresponding monomer was ranked hA(2A)AR > hA(1)AR ≥ hA(3)AR. The antagonist activity of the most potent conjugate 14 (34 xanthines per dendrimer) was examined at the G(i)-coupled A(1)AR. Conjugate 14 at 100 nM right-shifted the AR agonist concentration--response curve in a cyclic AMP functional assay in a parallel manner, but at 10 nM (lower than its K(i) value), it significantly suppressed the maximal agonist effect in calcium mobilization. This is the first systematic probing of a potent AR antagonist tethered on a dendrimer and its activity as a function of variable loading.