Regulation of feeding dynamics by the circadian clock, light and sex in an adult nocturnal insect

Animals invest crucial resources in foraging to support development, sustenance, and reproduction. Foraging and feeding behaviors are rhythmically expressed by most insects. Rhythmic behaviors are modified by exogenous factors like temperature and photoperiod, and internal factors such as the physiological status of the individual. However, the interactions between these factors and the circadian clock to pattern feeding behavior remains elusive. As Drosophila, a standard insect model, spends nearly all its life on food, we rather chose to focus on the adults of a non-model insect, Agrotis ipsilon, a nocturnal cosmopolitan crop pest moth having structured feeding activity. Our study aimed to explore the impact of environmental cues on directly measured feeding behavior rhythms. We took advantage of a new experimental set-up, mimicking an artificial flower, allowing us to specifically monitor feeding behavior in a naturalistic setting, e.g., the need to enter a flower to get food. We show that the frequency of flower visits is under the control of the circadian clock in males and females. Feeding behavior occurs only during the scotophase, informed by internal clock status and external photic input, and females start to visit flowers earlier than males. Shorter duration visits predominate as the night progresses. Importantly, food availability reorganizes the microstructure of feeding behavior, revealing its plasticity. Interestingly, males show a constant number of daily visits during the 5 days of adult life whereas females decrease visitations after the third day of adult life. Taken together, our results provide evidence that the rhythmicity of feeding behavior is sexually dimorphic and controlled by photoperiodic conditions through circadian clock-dependent and independent pathways. In addition, the use of the new experimental set-up provides future opportunities to examine the regulatory mechanisms of feeding behavior paving the way to investigate complex relationships between feeding, mating, and sleep-wake rhythms in insects.

The Behavioral Economics of Alcohol Demand in French and American University Students

BACKGROUND

Behavioral economic approaches have revealed several characteristics of alcohol demand (e.g., intensity, elasticity, and essential value) in university students; however, these approaches have not yet examined alcohol demand among students outside of the United States. The current study examined alcohol demand among student samples in the United States and France using a hypothetical alcohol purchase task (APT) and a novel APT Choice task, in which nonalcoholic beverages were concurrently available at a fixed low price.

METHODS

Participants at each site (United States, n = 132; France, n = 132) were asked to complete an Internet-based survey including the APT, APT Choice, Alcohol Use Disorders Identification Test, Daily Drinking Questionnaire, and Drinking Motives Questionnaire-Revised Short Form. Group demand functions were produced for each of the 2 samples in both country-specific and standardized drink units, and the exponential demand equation was fitted to each of the APT and APT Choice demand curves. Slope analyses were performed on the Non-Alcoholic Cross-Price demand to assess substitutability.

RESULTS

APT data revealed that in both samples, alcohol price and consumption were inversely related and demand measures were significantly associated with other alcohol measures. In addition, the availability of a nonalcoholic alternative reduced alcohol demand in both samples, with evidence of substitutability revealed by increases in cross-price consumption.

CONCLUSIONS

Low-cost alcohol is associated with increased alcohol consumption in both French and U.S. university students, and concurrent availability of a nonalcoholic beverage within the APT both reduces alcohol demand and demonstrates behavioral economic substitutability. These findings will inform future studies investigating behavioral and environmental factors underlying transcultural differences and specific prevention efforts.

A portable system for studying discrete-trial group choice

Whether groups of people or animals behave optimally in relation to resources is an issue of interest to psychology, ecology, and economics. In behavioral ecology, the simplest model of optimal group choice is the ideal free distribution (IFD). The IFD model has been tested in humans with discrete or continuous inputs and through manual or automated procedures (e.g., Kraft, Baum, & Burge, 2002; Madden, Peden, & Yamagushi, 2002). Manual procedures tend to be time consuming, however, whereas automated procedures typically require access to a computer network. In this article, we describe a new automated system for discrete-trial tests of the IFD model. Our protocol involves a single computer connected to a digital projector (for stimulus presentation) and a network of gamepads (for registering choices). The system is comparatively inexpensive, easy to install, easy to transport, and it permits the automated collection of group data in minimal time. We show that the data generated through this protocol are comparable to those previously reported in the IFD literature.

An assessment of fixed interval timing in free-flying honey bees (Apis mellifera ligustica): an analysis of individual performance

Interval timing is a key element of foraging theory, models of predator avoidance, and competitive interactions. Although interval timing is well documented in vertebrate species, it is virtually unstudied in invertebrates. In the present experiment, we used free-flying honey bees (Apis mellifera ligustica) as a model for timing behaviors. Subjects were trained to enter a hole in an automated artificial flower to receive a nectar reinforcer (i.e. reward). Responses were continuously reinforced prior to exposure to either a fixed interval (FI) 15-sec, FI 30-sec, FI 60-sec, or FI 120-sec reinforcement schedule. We measured response rate and post-reinforcement pause within each fixed interval trial between reinforcers. Honey bees responded at higher frequencies earlier in the fixed interval suggesting subject responding did not come under traditional forms of temporal control. Response rates were lower during FI conditions compared to performance on continuous reinforcement schedules, and responding was more resistant to extinction when previously reinforced on FI schedules. However, no "scalloped" or "break-and-run" patterns of group or individual responses reinforced on FI schedules were observed; no traditional evidence of temporal control was found. Finally, longer FI schedules eventually caused all subjects to cease returning to the operant chamber indicating subjects did not tolerate the longer FI schedules.

Social reinforcement delays in free-flying honey bees (Apis mellifera L.)

Free-flying honey bees (Apis mellifera L.) reactions were observed when presented with varying schedules of post-reinforcement delays of 0 s, 300 s, or 600 s. We measured inter-visit-interval, response length, inter-response-time, and response rate. Honey bees exposed to these post-reinforcement delay intervals exhibit one of several patterns compared to groups not encountering delays, and had longer inter-visit-intervals. We observed no group differences in inter-response time. Honey bees with higher response rates tended to not finish the experiment. The removal of the delay intervals increased response rates for those subjects that completed the trials.

Ethanol self-administration in free-flying honeybees (Apis mellifera L.) in an operant conditioning protocol

BACKGROUND

This study examines the effect of ethanol (EtOH) on continuous reinforcement schedules in the free-flying honeybee (Apis mellifera L.). As fermented nectars may be encountered naturally in the environment, we designed an experiment combining the tools of laboratory research with minimal disturbance to the natural life of honeybees.

METHODS

Twenty-five honeybees were trained to fly from their colonies to a fully automated operant chamber with head poking as the operant response. Load size, intervisit interval, and interresponse times (IRTs) served as the dependent variables and were monitored over the course of a daily training session consisting of many visits. Experimental bees were tested using an ABA design in which sucrose only was administered during condition A and a 5% EtOH sucrose solution was administered during condition B. Control bees received sucrose solution only.

RESULTS

Most bees continued to forage after EtOH introduction. EtOH significantly reduced the load size and the intervisit interval with no significant effect on IRTs. However, a look on individual data shows large individual differences suggesting the existence of different kinds of behavioral phenotypes linked to EtOH consumption and effects.

CONCLUSIONS

Our results contribute to the study of EtOH consumption as a normal phenomenon in an ecological context and open the door to schedule-controlled drug self-administration studies in honeybees.

The effect of pymetrozine (Plenum WG-50) on proboscis extension conditioning in honey bees (Apis mellifera: Hybrid var. Buckfast)

Experiments are designed to examine the effects of pymetrozine (Plenum WG-50), a recent systemic pesticide of the pyridine-azomethin family, on Pavlovian conditioning of harnessed foragers. In one set of experiments bees learned a task in which they associated a conditioned stimulus with feeding. A second set of experiments required the bees to learn a discrimination task. Within each experiment, bees received 5 μl of sucrose only, the recommended field dose of Plenum (5 μL of .3 gL(-1), .16 gL(-1) of pymetrozine measured), or 100 times the field dose of Plenum WG 50 thirty minutes prior to training (5 μL of 30 gL(-1), 14 gL(-1) of pymetrozine measured). The Plenum WG 50 was diluted with .88 M sucrose to facilitate the drinking of the pesticide. In addition to varying the concentration, we also investigated the effect of Plenum WG 50 on bees confined to an observation hive and a hive located outside. The results indicated that prior exposure to Plenum WG 50 affected Pavlovian conditioning only when bees were exposed to 100 times the recommended dosage.

A paradigm for operant conditioning in blow flies (Phormia terrae novae Robineau-Desvoidy, 1830)

An operant conditioning situation for the blow fly (Protophormia terrae novae) is described. Individual flies are trained to enter and reenter a hole as the operant response. Only a few sessions of contingent reinforcement are required to increase response rates. When the response is no longer followed by food, the rate of entering the hole decreases. Control procedures revealed that rate of responding is not a simple overall result of feeding or of aging. The flies entered into the hole only if the response was required to obtain the food.

Human group behavior: the ideal free distribution in a three-patch situation

A group of 15 college students was exposed to repeated trials of a task in which money was available for choosing among three colors (blue, red, and green). The amount of winning tokens for each color was varied across phases to test whether group distribution would track the ratio of winning tokens between patches. Confirming previous reports on ideal free performance in humans, group choice proved sensitive to the available resources but tended to undermatch the ratio of winning tokens. The difference-equalization rule of Sokolowski, Tonneau, and Freixa i Baqué [Psychonom. Bull. Rev. 6 (1999) 157] gave a satisfactory fit to the data.