Tracking of food quantity by coyotes (Canis latrans)

Previous studies have demonstrated that Weber's Law mediates quantitative discrimination abilities across various species. Here, we tested coyotes’ (Canis latrans) ability to discriminate between various quantities of food and investigated whether this ability conforms to predictions of Weber's Law. We demonstrate herein that coyotes are capable of reliably discriminating large versus small quantities of discrete food items. As predicted by Weber's Law, coyotes’ quantitative discrimination abilities are mediated by the ratio between the large and small quantities of food and exhibit scalar variability. Furthermore, in this task coyotes were not discriminating large versus small quantities based on olfactory cues alone.     

Dietary correlates of temporomandibular joint morphology in New World primates

Previous analyses of the masticatory apparatus have demonstrated that the shape of the temporomandibular joint (TMJ) is functionally and adaptively linked to variation in feeding behavior and diet in primates. Building on previous research, this study presents an analysis of the link between diet and TMJ morphology in the context of functional and dietary differences among New World primates. To evaluate this proposed relationship, I used three-dimensional morphometric methods to quantify TMJ shape across a sample of 13 platyrrhine species. A broad interspecific analysis of this sample found strong relationships among TMJ size, TMJ shape, and diet, suggesting that both size and diet are significant factors influencing TMJ morphology in New World primates. However, it is likely that at least some of these differences are related to a division of dietary categories along clade lines.A series of hypotheses related to load resistance capabilities and range of motion in the TMJ were then tested among small groups of closely related taxa with documented dietary differences. These pairwise analyses indicate that some aspects of TMJ morphology can be used to differentiate among closely related species with different diets. However, not all of my predictions were upheld. The anteroposterior dimensions of the TMJ were most strongly consistent with hypothesized differences in ingestive/masticatory behaviors and jaw gape, whereas the predictions generated for variation in entoglenoid and articular tubercle height were not upheld. These results imply that while some features can be reliably associated with increased load resistance and facilitation of wider jaw gapes in the masticatory apparatus, other features are less strongly correlated with masticatory function.     

Newborn GnRH neurons in the adult forebrain of the ring dove

The preoptic area of the hypothalamus is a key area that produces gonadotrophin-releasing hormone (GnRH). In birds, the chicken GnRH-I-form neurons are responsible for the hypothalamus-pituitary-gonadal system, which controls reproduction. In the ring dove, electrolytic lesion in the adult hypothalamus induces neurogenesis. In this study, we determined whether adult neurogenesis is involved in repairing GnRH neurons, specifically by generating newborn cells exhibiting GnRH-I immunoreactive properties. We selectively applied electrolytic lesions to three different regions of the diencephalon, including the preoptic area, which contains GnRH-I neurons, and identified new cells (BrdU-positive cells) that co-labeled with GnRH-I-immunoreactive cells. The BrdU⁺/GnRH⁺ double labeled cells were then confirmed with confocal laser analysis. In brains of both male and female ring doves we found new neurons at the lesion site of the preoptic region that were GnRH-I immunoreactive. However, the total number of GnRH neurons in the lesioned brains was less than that of sham-lesioned brains. When two other regions of the diencephalon that contain GnRH-I neurons were damaged, no recruitment of new GnRH-I neurons was detected. The rate of neurogenesis depends on the bird's reproductive phase when the lesion was applied. We found BrdU⁺/GnRH⁺ double-labeled cells almost exclusively during the pre-laying phase when birds are engaged in active courtship that leads to egg laying. Our observations suggest that recruitment of GnRH immunoreactive new neurons is restricted to the hypothalamic region and is sensitive to the reproductive stage of the birds.     

Quantitative genetics of natural variation of behavior in Drosophila melanogaster: the possible role of the social environment on creating persistent patterns of group activity

Using a set of nine effectively isogenic lines collected from nature in 1998, we observed unperturbed behaviors of mixed-sex groups of Drosophila melanogaster. We repeatedly scanned replicated groups of genetically identical individuals, five females and five males, and recorded the behavior of each individual (i.e., walking, feeding, grooming, flying, courting, mating, fighting, or resting). From these behaviors, we made a composite variable of activity for our quantitative genetic analysis. Genotypes differed in activity, explaining 14.41% of the variation in activity; 8.60% of the variation was explained by a significant genotype x sex interaction, which signifies genetic variation for sexual dimorphism in behavior. Phenotypic plasticity explained 11.13% of the variation in activity. Different genotypes and sexes within genotypes had different rank orders of the component behaviors that contribute to activity. We found no effect of common rearing environment. Instead, differences between replicate groups within genotype accounted for 19.47% variation in activity, and activity was significantly repeatable across scans. This emergent group behavior is likely caused by differences between groups of interacting individuals, even though individuals were genetically identical across groups. Thus, emergent group behavior explained almost as much variation in activity as the combined sources of genetic variation (23.01%), and this is an additional level on which selection could operate: individuals and groups. We discuss how differences among groups could change patterns of additive genetic variation available for evolution. Furthermore, because the behavior of an individual is influenced by conspecifics, genotype interactions between individuals could contribute to indirect selection. Finally, if we consider activity as a syndrome governing all component behaviors with strong genetic correlations among behaviors within an individual, then these component behaviors cannot evolve independently. These results suggest that reductionist approaches of molecular behavior genetics may be incomplete and/or misleading when considering similar phenotypes at the population level or when trying to understand how behaviors evolve.     

Polyomavirus EGFP-pseudocapsids: analysis of model particles for introduction of proteins and peptides into mammalian cells

A vector for preparation of mouse polyomavirus capsid-like particles for transfer of foreign peptides or proteins into cells was constructed. Model pseudocapsids carrying EGFP fused with the C-terminal part of the VP3 minor protein (EGFP-VLPs) have been prepared and analysed for their ability to be internalised and processed by mouse cells and to activate mouse and human dendritic cells (DC) in vitro. EGFP-VLPs entered mouse epithelial cells, fibroblasts and human and mouse DC efficiently and were processed by both, lysosomes and proteasomes. Surprisingly, they did not induce upregulation of DC co-stimulation molecules or maturation markers in vitro; however, they did induce interleukin 12 secretion.     

"Neuroethoendocrinology": integration of field and laboratory studies in insect neuroendocrinology

Progress in the field of insect neuroendocrinology has been rapid despite the relatively small number of investigators working on insect systems. This progress, in part, reflects the ease of studying insect behavior in the laboratory, and a historical perspective reveals that insect neuroendocrinology has been dominated since its inception by laboratory studies. Recent advances in methodology and a renewed interest in the concept of behavioral state in insects suggest that it might be useful for insect neuroendocrinologists to spend a little more time in the field.     

Changes of enzyme activity in lipid signaling pathways related to substrate reordering

The static fluid mosaic model of biological membranes has been progressively complemented by a dynamic membrane model that includes phospholipid reordering in domains that are proposed to extend from nanometers to microns. Kinetic models for lipolytic enzymes have only been developed for homogeneous lipid phases. In this work, we develop a generalization of the well-known surface dilution kinetic theory to cases where, in a same lipid phase, both domain and nondomain phases coexist. Our model also allows understanding the changes in enzymatic activity due to a decrease of free substrate concentration when domains are induced by peptides. This lipid reordering and domain dynamics can affect the activity of lipolytic enzymes, and can provide a simple explanation for how basic peptides, with a strong direct interaction with acidic phospholipids (such as beta-amyloid peptide), may cause a complex modulation of the activities of many important enzymes in lipid signaling pathways.     

Texture of locomotor path: a replicable characterization of a complex behavioral phenotype

A database of mouse locomotor path in spatial tests can be used to search in silico for behavioral measures that better discriminate between genotypes and are more replicable across laboratories. In this study, software for the exploration of exploration (SEE) was used to search a large database for a novel behavioral measure that would characterize complex movement paths. The database included mouse open-field behavior assessed in 3 laboratories, 7 inbred strains, several pharmacological treatments and hundreds of animals. The new behavioral measure, "path texture", was characterized using the local curvature of the path (the change of direction per unit distance, in degrees/cm) across several spatial scales, starting from scales smaller than the animal's body length and up to the scale of the arena size. Path texture analysis differs from fractal dimension analysis in that it does not assume self-similarity across scales. Path texture was found to discriminate inbred strains with relatively high broad-sense heritability (43%-71%) and high replicability across laboratories. Even genotypes that had similar path curvatures in some scales usually differed in other scales, and self-similarity across scales was not displayed by all genotypes. Amphetamine decreased the path curvature of C57BL/6 mice in small and medium scales, while having no effect on DBA/2J mice. Diazepam dose-dependently decreased the curvature of C57BL/6 mice across all scales, while 2 anxiogenic drugs, FG-7142 and pentylenetetrazole, increased it. Path texture thus has high potential for behavioral phenotyping and the study of drug effects in the mouse.     

A method for generating natural and user-defined sniffing patterns in anesthetized or reduced preparations

Sniffing has long been thought to play a critical role in shapingneural responses to odorants at multiple levels of the nervoussystem. However, it has been difficult to systematically examinehow particular parameters of sniffing behavior shape odorant-evokedactivity, in large part because of the complexity of sniffingbehavior and the difficulty in reproducing this behavior inan anesthetized or reduced preparation. Here we present a methodfor generating naturalistic sniffing patterns in such preparations.The method involves a nasal ventilator whose movement is controlledby an analog command voltage. The command signal may consistof intranasal pressure transients recorded from awake rats andmice or user-defined waveforms. This "sniff playback" devicegenerates intranasal pressure and airflow transients in anesthetizedanimals that approximate those recorded from the awake animaland are reproducible across trials and across preparations.The device accurately reproduces command waveforms over an amplituderange of approximately 1 log unit and up to frequencies of approximately12 Hz. Further, odorant-evoked neural activity imaged duringsniff playback appears similar to that seen in awake animals.This method should prove useful in investigating how the parametersof odorant sampling shape neural responses in a variety of experimentalsettings.     

Rattus exulans and the catastrophic disappearance of Hawai’i’s native lowland forest

Paleoenvironmental and archaeological investigations from the ’Ewa Plain of O’ahu provide insight into the problem of understanding lowland native forest loss in Hawai’i. Data from pollen analysis of a pond core record, avian paleontology, and archeology, document a precipitous decline of the native forest starting before Polynesian settlement on the ’Ewa Plain but after Polynesian colonization of O’ahu. It is hypothesized that rats, introduced by Polynesian colonizers, increased exponentially in the absence of significant predators or competitors, feeding on a largely endemic vegetation that had evolved in the absence of mammalian predators. Rats radiated ahead of human colonizers on O’ahu, eating their way through the vegetation, perhaps before the colonizers had encountered much of the pristine lowland forest into which the rats had radiated. This hypothesis is supported by several observations, including the almost complete absence of extinct or extirpated avian faunal remains in archaeological deposits, the present distribution of endemic vegetation in Hawai’i, rat ecology, population biology, and other evidence.