Browsing by Subject "Parasite"
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Item Dispersal of Attaphila fungicola, a symbiotic cockroach of leaf-cutter ants(2021-11-16) Phillips, Zachary Isaac; Gilbert, Lawrence E.; Mueller, Ulrich G.; Jha, Shalene; Beach, TimothyAnimal dispersal between habitats is difficult to observe from beginning to end. This is especially true of tiny, cryptic animals resistant to tracking methods. Attaphila fungicola is a miniature cockroach that lives in the deep, subterranean nests of leaf-cutter ants, a symbiont of the leaf-cutters and their mutualist fungal gardens. The only conspicuous glimpse we get of A. fungicola dispersal is at the beginning of their journey, during the nuptial flight preparations of leaf-cutter colonies. During these preparations, A. fungicola hitchhikes on the colony’s female alates (winged queens), which, if successful, will mate mid-air with male alates, land and begin new leaf-cutter colonies as foundresses (workerless queens). Hitchhiking on female alates has long been interpreted as a roach behavior facilitating dispersal to incipient colonies of foundresses; however, incipient colonies likely represent much lower quality habitats than larger established colonies, and roaches may benefit by avoiding the former during dispersal in favor of arriving at the latter. I explore this possibility under a host-symbiont framework, describing A. fungicola’s dispersal to incipient host colonies as “vertical transmission,” and its dispersal between larger established colonies as “horizontal transmission.” By considering variation in host quality between incipient and established colonies, and by using surveys, lab and field experiments and a mathematical model, I find evidence that A. fungicola roaches are primarily horizontally transmitted between established colonies and may use a mode of roach dispersal that entails two hitchhiking steps – first on female alates emigrating from upstream host colonies, then on foragers returning to downstream host colonies (“The Texas Two-step”). These findings have broad implications for predicting the dispersal/transmission of organisms that co-disperse (e.g., hitchhike) with their host’s propagules (e.g., female alates, plant seeds) and validate the importance of incorporating colony development into studies of host-symbiont dynamics.Item The early life history and reproductive biology of Cymothoa excisa, a marine isopod parasitizing Atlantic croaker, (Micropogonias undulatus), along the Texas coast(2012-08) Cook, Colt William; Munguia, Pablo; Buskey, Ed; Walther, BenjaminParasite population dynamics and the evolution of life history characteristics are strongly correlated with the processes of host infection, survival within a host and reproduction, with each process posing a challenge to the parasitic lifestyle. Macroparasites living in marine environments have evolved extreme changes in physiology, morphology and life history traits to overcome these challenges. This study focused on the infective and reproductive stage of the parasitic isopod, Cymothoa excisa, a common parasite on Atlantic croaker, (Micropogonias undulatus), along the Texas coast. A two year survey identified infection rates and the relationship between fish density and size and parasite load, size and fecundity. Isopod morphology was quantified for each life stage, identifying shape transitions through ontogeny and sex change. Sex change in C. excisa was found to be driven by the absence of conspecific parasites within a host, where sex change only occurred in the first individual to arrive. To understand the infective stage of C. excisa parasite energetics and host detection mechanisms were tested. Parasites with free-living life stages have a narrow window to infect a host and have evolved a number of mechanisms to detect and locate a host. I used a series of energetic experiments to determine an infection window for free-swimming larvae (mancae) and behavioral response experiments testing both visual and chemical cues associated with host detection. Mancae were found to have a narrow infection window, where mancae began searching for a host as soon as they are born, but quickly switch to an ambush strategy to conserve energy. Mancae were also found to be responsive to both visual and chemical cues from its common fish host, as well as a non-host fish, indicating that chemical cues are used in host detection, but chemical specificity is not a mechanism that C. excisa uses to find its common host. The results from this study have implications to parasitic species and their hosts, as well as to other areas of study, including population and ecosystem dynamics.Item Plant figurations : a vital study in rhetorical address following Theodor W. Adorno(2018-04-13) Albiniak, Theodore Neal; Gunn, Joshua, 1973-; Davis, Diane; Brummett, Barry; Stroud, ScottIn this dissertation, I ask the question: how is (and is not) the plant both subject and object of human rhetoric? In taking up the question, I explore an array of texts, artifacts, and encounters revealing “the plant” addressed as a vital object of subjective experience and as a subject of objective reflection. Following what Diane Davis and Michelle Ballif call “extrahuman rhetorical relations,” I demonstrate an orientation of struggle that holds the question open at its limit, by approaching iterations of “the plant” caught in motion. I apply a method drawn from Frankfurt School scholar Theodor W. Adorno’s invitation to apply negative dialectics—or immanent criticism—to everyday sites of personal encounter and interdisciplinary texts. I understand the dialectic features of human-plant relations in three chapters or figures studies. First, I examine the concept of “natural history” revealed in a site-specific experience at Red Rock State Park in California. Second, I look at the historic and contemporary texts that name a parasitic liana known as the Sipo-Matador. Third, I hear the sounding of European trees emanating through a vinyl copy of the 2012 art-album Years by Bartholomäus Traubeck. Approaching these figures in affirmative and negative modes, I argue that keeping the dialectic in motion instantiates a critical process—a reflection on reflective capacity—across multiple renderings of representation and structure. Writing and reading is an essential part of this process. In understanding thinking as a movement of mediation—a dramatic journey joining the dialectic across theoretical abstraction and lived reality—I reveal a multidimensional orientation to rhetorical criticism suited to hear the plant, addressed. My approach, I argue, keeps Adorno and the plant—both subjects and objects of this dissertation—close enough to touch while at bay enough to remain mysterious. I trace a malignant structure surrounding my encounter between the human and the plant—the Enlightenment in its dominating iterations—in relief as much as I hope to leave open creative reflection and vital critique.