Rapid acquisition of preference in concurrent schedules: Effects of d-amphetamine on sensitivity to reinforcement amount

In the present study, effects of d-amphetamine on sensitivity to reinforcement amount under concurrent schedules were examined using a rapid-acquisition procedure. Four pigeons key pecked under single concurrent variable-interval 30-s schedules of grain presentation. Two different reinforcer-amount ratios (7:1 and 1:7) changed across sessions according to a 31-step pseudo-random binary sequence (PRBS). After at least four times through the PRBS, response ratios generally tracked the session-to-session changes in amount ratios; estimates of sensitivity ranged from 0.26 to 0.31 across the four pigeons. Effects of a range of doses of d-amphetamine (0.3-5.6 mg/kg) then were determined. For 3 of 4 pigeons, at least one dose, which did not dramatically alter overall response output or bias, decreased sensitivity to reinforcement amount. These results suggest that reducing sensitivity of responding to reinforcement amount may be one behavioral mechanism of stimulants, which may have implications for interpreting drug effects on self-control.     

Coupling historical prospection data and a remotely-sensed vegetation index for the preventative control of Desert locusts

Locusts are grasshopper species that exhibit phase polyphenism resulting in the expression of gregarious behaviors that favor the development of large devastating bands and swarms. Desert locust preventative management aims to prevent crop damage by controlling populations before they can reach high densities and form mass migrating swarms. The areas of potential gregarization for Desert locust are large and need to be physically assessed by survey teams for efficient preventative management. An ongoing challenge is to be able to guide where prospection surveys should occur depending on local meteorological and vegetation conditions. In this study, we analyzed the relationship between historical prospection data of Desert locust observations from 2005 to 2009 and spatio-temporal statistics of a vegetation index gathered by remote-sensing with the help of multiple models of logistic regression. The vegetation index was a composite Normalized Difference Vegetation Index (NDVI) given every 16 days and at 250 m spatial resolution (MOD13Q1 from MODIS satellite). The statistics extracted from this index were: (1) spatial means at different scales around the prospection point, (2) relative differences of NDVI variation through time before the prospection, and (3) large-scale summary of vegetation quantity. The multi-model framework showed that vegetation development a month and a half before the survey was amongst the best predictors of locust presence. Also, the local vegetation quantity was not enough to predict locust presence. Vegetation quantity on a scale of a few kilometers was a better predictor but varied non-linearly, reflecting specific biotope types that support Desert locust development. Using one of the best logistic regression models and NDVI data, we were able to derive a predictive model of probability of finding locusts in specific areas. This methodology should help in more efficiently focusing survey efforts on specific parts of the gregarization areas based on the predicted probability of locusts being present.     

A behavioral profile for stumptail macaques (Macaca arctoides)

Behavioral observations made on a group of 15 stumptail macaques living in a seminatural environment are used to delineate an activity profile for the species which embraces numerous locomotor, self-directed, environment-directed and social behaviors. Data indicating that certain animals direct or receive particular behaviors at markedly different rates than the rest of the group are noted. The data from 39,000 10-sec observational samples are used to construct a detailed behavioral time-budget for the group. The budget takes into account the co-occurrence rates of the most frequently observed behaviors with each other and with the other behaviors recorded. The activity profile constructed in this way is compared with the results of four other studies which estimate daily behavioral rates for the species. Environmental, social group composition and sampling-technique variables are considered for their probable effects upon the behavioral rates reported in both the present and the compared studies. A detailed comparison of data from the different studies permits the estimate of a species-typical rate for each of the behavioral patterns reported and commented upon. The estimated rates, expressed as a range of values indicating the percentage of time that an average group member dedicates to various behaviors, should be valid in a wide variety of environments.     

The effects of colony characteristics on life span and foraging behavior of individual wasps (Polybia occidentalis,Hymenoptera: Vespidae)

Summary We studied the effects of intrinsic colony characteristics and an imposed contingency on the life span and behavior of foragers in the swarm-founding social waspPolybia occidentalis. Data were collected on marked, known-age workers introduced into four observation colonies.To test the hypothesis that colony demographic features affect worker life span, we examined the relationships of colony age and size with worker life span using survivorship analysis. Colony age and size had positive relationships with life span; marked workers from two larger, older colonies had longer life spans (¯X = 24.7 days) than those from two smaller, younger colonies (¯X = 20.1 days).We quantified the effects of experimentally imposed nest damage on forager behavior, to determine which of three predicted behavioral responses by foragers to this contingency (increased probability of foraging for building material, increased rate of foraging, or decrease in age of onset of foraging) would be employed. Increasing the colony level of need for materials used in nest construction (wood pulp and water) by damaging the nests of two colonies did not cause an increase in either the proportion of marked workers that gathered nest materials or in foraging rates of marked individuals, when compared with introduced workers in two simultaneously observed control colonies. Instead, nest damage caused a decrease in the age at which marked workers first foraged for pulp and water. The response to an increase in the need for building materials was an acceleration of behavioral development in some workers.     

Opioid systems,behavioral thermoregulation and shell polymorphism in the land snail,Cepaea nemoralis

Summary Numerous ecological studies have dealt with the shell color and banding polymorphism of the land snail Cepaea nemoralis. The present field and laboratory investigations focus on the roles of opioid systems in modulating the thermal preferences and behavioral thermoregulation of various morphological types of Cepaea. Evidence is presented that differences in opioid modulation of the thermal responses of Cepaea are associated with shell polymorphism. It is shown that the effects of the prototypic opiate agonist, morphine, and antagonist, naloxone, on behavioral thermoregulation in Cepaea vary with the shell banding pattern and thermal microhabitat. In both the field and laboratory, morphine (0.10, 1.0 and 10 g per snail) caused significant dose- and time-dependent increases in the temperatures selected by various morphological types of Cepaea. The palest shell type (yellow, unbanded) with the highest basal preferred temperature displayed the greatest response to morphine, the shell type (yellow, 2-banded) with an intermediate basal preferred temperature showed an intermediate response to morphine, and the darkest shell type (yellow, 5-banded) with lowest basal preferred temperature showed the least increase in preferred temperature after administration of morphine. These effects of morphine were blocked and reversed by naloxone (1.0 g), with the opiate antagonist by itself (1.0 and 10 g) causing a significant decrease in behaviorally selected temperatures. The unbanded and 2-banded morphs displayed significantly greater decreases in preferred temperatures after treatment with naloxone than did the 5-banded morph, which showed minimal responses. It is suggested that these differences in opioid modulation of thermal preferences and behavioral thermoregulation may contribute to the polymorphic thermal preferences of natural populations of Cepaea.Abbreviations B yellow five-banded shell type - I yellow two-banded shell type - U yellow unbanded shell type     

Cope's rule and the adaptive landscape of dinosaur body size evolution

The largest known dinosaurs weighed at least 20 million times as much as the smallest, indicating exceptional phenotypic divergence. Previous studies have focused on extreme giant sizes, tests of Cope's rule, and miniaturization on the line leading to birds. We use non‐uniform macroevolutionary models based on Ornstein–Uhlenbeck and trend processes to unify these observations, asking: what patterns of evolutionary rates, directionality and constraint explain the diversification of dinosaur body mass? We find that dinosaur evolution is constrained by attraction to discrete body size optima that undergo rare, but abrupt, evolutionary shifts. This model explains both the rarity of multi‐lineage directional trends, and the occurrence of abrupt directional excursions during the origins of groups such as tiny pygostylian birds and giant sauropods. Most expansion of trait space results from rare, constraint‐breaking innovations in just a small number of lineages. These lineages shifted rapidly into novel regions of trait space, occasionally to small sizes, but most often to large or giant sizes. As with Cenozoic mammals, intermediate body sizes were typically attained only transiently by lineages on a trajectory from small to large size. This demonstrates that bimodality in the macroevolutionary adaptive landscape for land vertebrates has existed for more than 200 million years.     

Self-assembly of Mutant Huntingtin Exon-1 Fragments into Large Complex Fibrillar Structures Involves Nucleated Branching

Huntingtin (HTT) fragments with extended polyglutamine tracts self-assemble into amyloid-like fibrillar aggregates. Elucidating the fibril formation mechanism is critical for understanding Huntington's disease pathology and for developing novel therapeutic strategies. Here, we performed systematic experimental and theoretical studies to examine the self-assembly of an aggregation-prone N-terminal HTT exon-1 fragment with 49 glutamines (Ex1Q49). Using high-resolution imaging techniques such as electron microscopy and atomic force microscopy, we show that Ex1Q49 fragments in cell-free assays spontaneously convert into large, highly complex bundles of amyloid fibrils with multiple ends and fibril branching points. Furthermore, we present experimental evidence that two nucleation mechanisms control spontaneous Ex1Q49 fibrillogenesis: (1) a relatively slow primary fibril-independent nucleation process, which involves the spontaneous formation of aggregation-competent fibrillary structures, and (2) a fast secondary fibril-dependent nucleation process, which involves nucleated branching and promotes the rapid assembly of highly complex fibril bundles with multiple ends. The proposed aggregation mechanism is supported by studies with the small molecule O4, which perturbs early events in the aggregation cascade and delays Ex1Q49 fibril assembly, comprehensive mathematical and computational modeling studies, and seeding experiments with small, preformed fibrillar Ex1Q49 aggregates that promote the assembly of amyloid fibrils. Together, our results suggest that nucleated branching in vitro plays a critical role in the formation of complex fibrillar HTT exon-1 aggregates with multiple ends.     

The effect of shielding the parietal eye of Podarcis muralis on behavioral thermoregulation

1. 1. Body temperatures (T_bs) and thermoregulatory precision of 7 sham shielded and 7 parietal eye shielded Podarcis muralis were measured in a linear thigmothermal gradient over a 24 h period.

2. 2. Shielding the parietal eye did not alter the mean T_b selected over the 24 h period.

3. 3. Both groups selected T_bs that did not differ between photophase and scotophase.

4. 4. Shielding the parietal eye did not influence thermoregulatory precision when measured over the 12 h of photophase, but from 0600–1200 h EST parietal eye shielded lizards thermoregulated more precisely than sham shielded lizards.