Neonatal anesthesia for studies of hamster parental behavior when infanticidal aggression is a possibility

Experiments involving investigation of the neuroendocrine basis for paternal care in rodents risk activation of aggressive behavior toward pups. To minimize pain and suffering during tests of parental responsiveness requiring retrieval of a displaced pup to its nest, a method of anesthetizing the pup was developed in Djungarian hamsters, Phodopus campbelli. A surgical plane of anesthesia, as measured by criteria, such as respiratory depression, loss of the pedal reflex, and failure to increase respiratory rate or to vocalize in response to handling, was achieved by use of intraperitoneal administration of a combination of ketamine and xylazine. Both parents (tested separately) expressed normal behavior toward anesthetized pups. In random order, a saline-injected or anesthetized pup was displaced from its nest in the home cage. There were no differences in pick-up or retrieval rates between saline and anesthetized pups for either parent. A third test using an unmanipulated pup confirmed that parental behavior was not reduced toward an anesthetized pup. However, if anesthetized pups were tested first among littermates, retrieval by males was less likely. This method will, therefore, underestimate retrieval behavior in males, but not females. Adult male hamsters that had never been parents also expressed expected behavior by attacking the pup in 45% of cases. This method provides an efficient and effective means of protecting pups while allowing adults to express a wide range of parental and infanticidal behaviors. It also has application in behavioral screening of transgenic strains toward unrelated young.     

Using genetic markers to estimate the pollen dispersal curve

Pollen dispersal is a critical process that shapes genetic diversity in natural populations of plants. Estimating the pollen dispersal curve can provide insight into the evolutionary dynamics of populations and is essential background for making predictions about changes induced by perturbations. Specifically, we would like to know whether the dispersal curve is exponential, thin-tailed (decreasing faster than exponential), or fat-tailed (decreasing slower than the exponential). In the latter case, rare events of long-distance dispersal will be much more likely. Here we generalize the previously developed TWOGENER method, assuming that the pollen dispersal curve belongs to particular one- or two-parameter families of dispersal curves and estimating simultaneously the parameters of the dispersal curve and the effective density of reproducing individuals in the population. We tested this method on simulated data, using an exponential power distribution, under thin-tailed, exponential and fat-tailed conditions. We find that even if our estimates show some bias and large mean squared error (MSE), we are able to estimate correctly the general trend of the curve - thin-tailed or fat-tailed - and the effective density. Moreover, the mean distance of dispersal can be correctly estimated with low bias and MSE, even if another family of dispersal curve is used for the estimation. Finally, we consider three case studies based on forest tree species. We find that dispersal is fat-tailed in all cases, and that the effective density estimated by our model is below the measured density in two of the cases. This latter result may reflect the difficulty of estimating two parameters, or it may be a biological consequence of variance in reproductive success of males in the population. Both the simulated and empirical findings demonstrate the strong potential of TWOGENER for evaluating the shape of the dispersal curve and the effective density of the population (d(e)).     

Learning strengthens the response of primary visual cortex to simple patterns

Training can significantly improve performance on even the most basic visual tasks, such as detecting a faint patch of light or determining the orientation of a bar (for reviews, see ). The neural mechanisms of visual learning, however, remain controversial. One simple way to improve behavior is to increase the overall neural response to the trained stimulus by increasing the number or gain of responsive neurons. Learning of this type has been observed in other sensory modalities, where training increases the number of receptive fields that cover the trained stimulus. Here, we show that visual learning can selectively increase the overall response to trained stimuli in primary visual cortex (V1). We used functional magnetic resonance imaging (fMRI) to measure neural signals before and after one month of practice at detecting very low-contrast oriented patterns. Training increased V1 response for practiced orientations relative to control orientations by an average of 39%, and the magnitude of the change in V1 correlated moderately well with the magnitude of changes in detection performance. The elevation of V1 activity by training likely results from an increase in the number of neurons responding to the trained stimulus or an increase in response gain.     

Spermatozoal traits and sperm competition in Atlantic salmon: relative sperm velocity is the primary determinant of fertilization success

Sperm competition occurs when sperm from more than one male compete for fertilizations. This form of post-copulatory sexual selection is recognized as a significant and widespread force in the evolution of male reproductive biology and as a key determinant of differential male reproductive success. Despite its importance, however, detailed mechanisms of sperm competition at the gamete level remain poorly understood. Here, we use natural variation in spermatozoal traits among wild Atlantic salmon (Salmo salar), a species naturally adapted to sperm competition, to examine how the relative influences of sperm (i) number, (ii) velocity, (iii) longevity, and (iv) total length determine sperm competition success. Atlantic salmon fertilize externally, and we were therefore able to conduct controlled in vitro fertilization competitions while concurrently measuring spermatozoal traits within the aqueous micro-environment to which salmon gametes are naturally adapted. Microsatellite DNA fingerprinting revealed that a male's relative sperm velocity was the primary determinant of sperm competition success. There was no significant relationship between fertilization success and either relative sperm number or total length; sperm longevity showed an inverse relationship with competition success. These relationships were consistent for two experimental repeats of the in vitro fertilization competitions. Our results therefore show, under the natural microenvironment for salmon gametes, that relative sperm velocity is a key spermatozoal component for sperm competition success. Atlantic salmon sperm can be considered to enter a competition analogous to a race in which the fastest sperm have the highest probability of success.     

Patterns of MHC selection in African mole-rats, family Bathyergidae: the effects of sociality and habitat

African mole-rats are a family of rodents exhibiting an eclectic range of social behaviour and occupying a variety of habitat types. These differences are likely to impact upon the risk of parasite transmission and virulence, with increasing sociality predicted to correspond to an increased risk of transmission. We investigate these factors by analysing the major histocompatibility complex (MHC), a set of genes responsible for encoding highly variable intermediaries of the vertebrate adaptive immune response. To this end we assessed selection at exons 2 and 3 of the MHC class II DQalpha1 gene of four African mole-rat species representing a range of social behaviours. We demonstrate that: (i) the overall pattern of selection at these exons differentiates according to the predicted function of different regions, with the presence of positive selection indicating the likely influence of host-parasite coevolution; and (ii) contrary to the often observed and predicted positive correspondence between sociality and the risk of parasite transmission, two highly social African mole-rat species in fact appear to have comparatively weak positive selection, suggesting diminished host immunity and thus a low overall risk of parasite transmission.     

Do aposematism and Batesian mimicry require bright colours? A test,using European viper markings.

Predator avoidance of noxious prey, aposematism and defensive mimicry are normally associated with bright, contrasting patterns and colours. However, noxious prey may be unable to evolve conspicuous coloration because of other selective constraints, such as the need to be inconspicuous to their own prey or to specialist predators. Many venomous snakes, particularly most vipers, display patterns that are apparently cryptic, but nevertheless highly characteristic, and appear to be mimicked by other, non-venomous snakes. However, predator avoidance of viper patterns has never been demonstrated experimentally. Here, the analysis of 813 avian attacks on 12,636 Plasticine snake models in the field shows that models bearing the characteristic zigzag band of the adder (Vipera berus) are attacked significantly less frequently than plain models. This suggests that predator avoidance of inconspicuously but characteristically patterned noxious prey is possible. Our findings emphasize the importance of mimicry in the ecological and morphological diversification of advanced snakes.     

Uterine receptivity and the plasma membrane transformation

This review begins with a brief commentary on the diversity of placentation mechanisms, and then goes on to examine the extensive alterations which occur in the plasma membrane of uterine epithelial cells during early pregnancy across species. Ultrastructural, biochemical and more general morphological data reveal that strikingly common phenomena occur in this plasma membrane during early pregnancy despite the diversity of placental types--from epitheliochorial to hemochorial, which ultimately form in different species. To encapsulate the concept that common morphological and molecular alterations occur across species, that they are found basolaterally as well as apically, and that moreover they are an ongoing process during much of early pregnancy, not just an event at the time attachment, the term ‘plasma membrane transformation‘ is suggested which also emphasises that alterations in this plasma membrane during early pregnancy are key to uterine receptivity.     

NO means no and yes: regulation of cell signaling by protein nitrosylation

Protein nitrosylation is emerging as a key mechanism by which nitric oxide regulates cell signaling. Nitrosylation is the binding of a NO group to a metal or thiol (-SH) on a peptide or protein. Like phosphorylation, nitrosylation is a precisely targeted and rapidly reversible posttranslational modification that allows cells to flexibly and specifically respond to changes in their environment. An increasing number of proteins have been identified whose activity is regulated by intracellular nitrosylation. This review focuses on proteins regulated by endogenous nitrosylation, the chemistry underlying nitrosylation, the specificity and reversibility of nitrosylation reactions, methods to detect protein nitrosylation, and the role of coordinated protein nitrosylation/denitrosylation in cell signaling.     

P-type ATPase heavy metal transporters with roles in essential zinc homeostasis in Arabidopsis

Arabidopsis thaliana has eight genes encoding members of the type 1_B heavy metal–transporting subfamily of the P-type ATPases. Three of these transporters, HMA2, HMA3, and HMA4, are closely related to each other and are most similar in sequence to the divalent heavy metal cation transporters of prokaryotes. To determine the function of these transporters in metal homeostasis, we have identified and characterized mutants affected in each. Whereas the individual mutants exhibited no apparent phenotype, hma2 hma4 double mutants had a nutritional deficiency phenotype that could be compensated for by increasing the level of Zn, but not Cu or Co, in the growth medium. Levels of Zn, but not other essential elements, in the shoot tissues of a hma2 hma4 double mutant and, to a lesser extent, of a hma4 single mutant were decreased compared with the wild type. Together, these observations indicate a primary role for HMA2 and HMA4 in essential Zn homeostasis. HMA2promoter- and HMA4promoter-reporter gene constructs provide evidence that HMA2 and HMA4 expression is predominantly in the vascular tissues of roots, stems, and leaves. In addition, expression of the genes in developing anthers was confirmed by RT-PCR and was consistent with a male-sterile phenotype in the double mutant. HMA2 appears to be localized to the plasma membrane, as indicated by protein gel blot analysis of membrane fractions using isoform-specific antibodies and by the visualization of an HMA2-green fluorescent protein fusion by confocal microscopy. These observations are consistent with a role for HMA2 and HMA4 in Zn translocation. hma2 and hma4 mutations both conferred increased sensitivity to Cd in a phytochelatin-deficient mutant background, suggesting that they may also influence Cd detoxification.