1,721,031 research outputs found
Recommended from our members
Integration of Functional Systems: Assessing the Use of the Locomotor System During Prey Capture in Fishes
Get PDFOrganismal complexity is often reduced to individual systems, but organisms function as an integrated whole and reductionist studies cannot address the constraints imposed by systems working together to perform a function. In this dissertation, I use integration between locomotor and feeding performance during prey capture in fishes as a model system for understanding complex behaviors and their ecological relevance. First, I demonstrate the empirical utility of integration for describing emergent differences between species. I utilize two species of Pacific marine sculpins capturing live amphipod prey, and confirmed that species were similar in feeding behaviors but different in their use of locomotion during prey capture. This resulted in differences in integration that reflect ecological divergence that would not be apparent in feeding behaviors alone. Second, I demonstrate that differential capture success is due to differences in predator accuracy. I utilize centrarchid sunfishes to develop a non-invasive model of suction volume and accuracy and apply this model to 3D feeding kinematics of three predators capturing two prey types. Not only did accuracy vary across species, but so did the ability to modulate the shape of the ingested volume of water, leading to a direct effect on predator capture success. Finally, I expand the techniques for quantifying behavioral integration to multivariate space and assess the causes and consequences of integration using a single centrarchid predator capturing two prey types. Partial least squares correlations describe multivariate integration and demonstrate that predators rely on performance variables differentially for each prey type. These differences are then reflected in patterns of integration and predator accuracy across prey types. This dissertation advances our understanding of how organismal integration and complexity act to drive performance and ecology. I demonstrate that performance integration is real and can be quantified and establish the empirical and ecological relevance of performance integration. Integration and organismal complexity may be one of the next scientific frontiers, and this dissertation provides a first step in exploring this new direction
Recommended from our members
Function, Morphology, and Evolution of Gecko Locomotion: The Importance of Ecology and Substrate
Get PDFLocomotion is a central tenet of life for many organisms that is inherently tied to the surrounding physical environment. Geckos represent a speciose and phenotypically diverse clade of lizards that are found within many habitats and move on a variety of substrates. Although much is now known about the integration and mechanics of the highly adept frictional adhesive toe pads from intensive laboratory study within model species, the functional and evolutionary significance of phenotypic diversity within geckos is ripe for investigation. This dissertation thus brings ecological context to the foreground to begin to address this large gap. In Chapter 1, we collected field observations and locomotor trials of surface compliance transitions in a cursorial day gecko, Rhoptropus afer, to examine how this species responds to sudden changes in substrate conditions encountered in nature. This species maintained high-speed running while altering its posture and stance time when transitioning into and out of sand collected from its habitat. In Chapter 2, we used experimental claw manipulation (i.e., partial removal) in the arboreal species, Thecadactylus rapicauda, to assess the functional interplay of adhesive toe pads and claws on natural and artificial surfaces of different roughness. After partial claw removal, static clinging performance significantly declined on non-smooth surfaces, and geckos tended to adjust their foot kinematics to increase contact duration on smooth and rough surfaces at both horizontal and low incline, although their ability to accelerate from a stationary position was not significantly altered. Finally, in Chapter 3, we took a phylogenetic comparative approach (112 gecko species) to test if morphological variation in toe pads and claws represents adaptive evolution to general habitat use. We found that species using more scansorial habitats tended to have larger, longer pads and more curved claws, with saxicolous species having longer setae than all other groups
Recommended from our members
Form, Function, and Evolution of Shark Pectoral Fins
Get PDFThe origin and evolution of pectoral fins remains one of the most important components of vertebrate history. Sharks represent one of the oldest representatives to exhibit paired fins. Yet, there is a paucity of data on the functional and evolutionary aspects of shark pectoral fins. This dissertation aims to bridge those gaps. In Chapter 1, we measured the external pectoral fin morphology of a shark species, the scalloped hammerhead (Sphyrna lewini), that undergoes ecological shifts through ontogeny. We found the pectoral fins changed in shape that are most likely in response the difference in ecological demands that this shark experiences. In Chapter 2, we measured the pectoral fin aspect ratio (AR) of nearly every known (89%) extant shark species and various extinct species. In addition, we coded each species based on their ecology and performed sophisticated evolutionary model fitting analyses. We determined sharks were most likely benthic (i.e., bottom-dwelling) or benthopelagic (i.e., near bottom) in origin and that when sharks shifted to the pelagic (open water) zone of the marine ecosystem, their pectoral fin morphology also changed, clearly demonstrating adaptive evolution. We also realized temperature was a critical driver in shark evolution. In Chapter 3, we used the computational fluid dynamics (CFD) approach to understand the functional aspects of pelagic shark pectoral fins. Our results showed that pelagic shark pectoral fins have different functions compared to benthic sharks. In Chapter 4, we followed up our work in Chapter 1, and compared the scaling trends of shark pectoral fins with various ecologies to determine if any noticeable patterns were present. We realized the scaling of shark pectoral fins is highly complex and that further broader research is warranted
Recommended from our members
Kinematics and Mechanics of Jumping Lizards: the Modulation of Jump Power
Get PDFIn order to understand the evolution of locomotion, lizards are often used to study the relationships between morphology and locomotor performance. However, the mechanisms by which himblimb morphology results in jumping performance are not well understood, despite the fact that jumping may be important for fitness in many lizard species.Here I investigate the ways in which mechanical power is generated by the hindlimbs of jumping collared lizards, Crotaphytus collaris. I examine the contribution of each hindlimb joint to total power output. I also test the hypothesis that these lizards utilize elastic power amplification.I found a high degree of individual variation in the relationships between joint kinematics and jump power, suggesting multiple strategies for controlling jump performance and highlighting the importance for considering individual variation in biomechanical studies. I also found peak power outputs exceeding the physiological limits of lizard muscle suggesting the presence of a power amplification mechanism. Additionally, the use of countermovements may enhance jump power, though possibly through mechanisms other than elastic energy storage
Recommended from our members
Kinematic and Neuromuscular Basis of Arboreal Locomotion in Anolis Lizards
Get PDFLocomotion is an integral component of the majority of behaviors that dictate the survival of vertebrates. However, the environments through which animals move are often heterogeneous. The arboreal habitat may be one of the most challenging environments due to its wide variation in substrate incline, diameter, compliance, and texture. This array of structural challenges places extreme and varied demands on the locomotor system that muscles, as the units that power this system, must be able to cope with. Although we have a good understanding of the kinematic and neuromuscular modifications employed by animals encountering different inclines, we know virtually nothing about how other structural challenges affect locomotor behavior and in vivo muscle function. In this dissertation, I used a combination of high-speed video, electromyography, in situ contractile experiments, and morphology to understand how arboreal Anolis lizards modulate their behavior and power cyclical locomotion on surfaces of varying incline and perch diameter. Several significant results emerged. First, the forelimb and hind limb were modulated differently in response to changes in substrate; the forelimb likely adopts a greater propulsive role and the hind limb a more stabilizing role on steeper inclines and narrower surfaces. Second, there was a decoupling of the response of limb movements and motor patterns to changes in substrate; perch diameter had a stronger effect on kinematics than incline, whereas muscle activity was more strongly affected by incline than by perch diameter. Third, not only does muscle recruitment, operating length, and capacity for force production change with perch diameter to allow the gastrocnemius, a primary ankle extensor, to contribute more to propulsion on broader than on narrower surfaces, but incline appears to alter the relationship between muscle recruitment and efficiency of force production. Finally, hind limb tendons do not appear to have the potential to stretch and store significant elastic energy during cyclical locomotion in Anolis lizards. Together these data force us to acknowledge the complex nature of mechanisms that power locomotion in the natural world. The environment can clearly have a profound impact on both the coordinated function of limbs and the neural control and physiology of the muscles that power locomotor behaviors
Recommended from our members
An Integrative Analysis of Gecko Foot Morphology in Relation to the Evolution of the Adhesive System
Get PDFThe foot is a crucial component to locomotion and is greatly affected by the evolution of new functions. This dissertation examines both functional and morphological aspects of how the evolution of the dry adhesive system is associated with the evolution gecko feet. In Chapter 1, I obtained obtained 3D movements (with high-speed video) of geckos (Phelsuma madagascariensis) running on a range of ecologically relevant inclines to examine in detail, how geckos modulate their feet with the dry adhesive system. We focused on measuring instantaneous within-foot symmetry and foot alignment relative to the body. On smaller perch diameters, geckos inverted their foot alignment and the hind foot had greater individual digit modulation than the forefoot.Chapter 2 used a comparative phylogenetic framework to examine how digit morphology and within-foot symmetry changed with the evolution of the adhesive system. I applied geometric morphometric methods to X-rays obtained of both padbearing and padless geckos. Our results confirm that padbearing lineages tend to have shorter digits, greater within-foot symmetry and larger interdigital angles than padless lineages and this suggests repeated shifts to a similar pad-bearing morphology.In Chapter 3, I obtained microCT scans of padbearing and padless lineages to examine how the evolution of the adhesive system is associated with shape change in the bones (astragalocalcaneum and the fourth distal tarsal) involved in the mesotarsal joint. Our results show that padbearing lineages likely have greater degrees of freedom at the mesotarsal joint as a result of having broader surfaces on the astragalocalcaneum and fourth distal tarsal
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Recommended from our members
From Ambush to Activity: Using Accelerometry to Reveal Cryptic Behaviors of Rattlesnakes and Kangaroo Rats
Get PDFIn my first chapter, I review the behavioral characteristics, functional morphology, biomechanics, and taxonomic diversity of ambush hunting in snakes. Specifically, I discuss and review the decision-making process and behavioral stages involved in choosing an ambush site, the functional morphology and biomechanics behind the predatory strike of an ambush hunting snake, and what is known about the prevalence of ambush hunting within and between snake taxa. In my second chapter, I propose a new method to quantify key aspects of the feeding behavior of three species of viperid snakes (Crotalus spp.) and assess the transferability of classification models across those species. I used open-source software to create species-specific models that classified locomotion, stillness, predatory striking, and prey swallowing with high precision, accuracy, and recall. In addition, we identified a low cost, reliable, non-invasive attachment method for accelerometry devices to be placed anteriorly on snakes, as is likely necessary for accurately classifying distinct behaviors in these species. In my third chapter, I provide a proof-of-concept approach to effectively quantify behavioral patterns of small bodied (< 50 g), nocturnal, and terrestrial free-ranging mammals using large acceleration datasets by combining low-mass, miniaturized animal-borne accelerometers with radiotelemetry and advanced machine learning techniques. We developed a method of attachment and retrieval for deploying accelerometers, a non-disruptive method of gathering observational validation datasets for acceleration data on free-ranging nocturnal small mammals and used these techniques on Merriam’s kangaroo rats to analyze how behavioral patterns relate to abiotic factors. We found that Merriam’s kangaroo rats are only active during the nighttime phases of the diel cycle and are particularly active during later light phases of the night (i.e., late night, morning twilight, and dawn). We found no reduction in activity or foraging associated with moonlight, indicating that kangaroo rats are actually more lunarphilic than lunarphobic. We also found that kangaroo rats increased foraging effort on more humid nights, most likely as a mechanism to avoid cutaneous water loss. My dissertation collectively provides a synthesis of ambush hunting in snakes and highlights the power of biologging technologies to overcome traditional challenges in studying cryptic and nocturnal species
- …
