Graduation date: 1995

Thesis (Ph. D.)--University of Washington, 1984. / Vita. Bibliography: leaves [129]-141.

Thesis (Ph. D.)--Murdoch University, 1999. / Includes bibliographical references (leaves 116-130).

Graduation date: 1992

In higher vertebrates, normal digestion and absorption by the gastrointestinal tract are dependent on the orderly and controlled transit of intraluminal contents. A relationship between fluid passage through the gut and absorption from the gut has yet to be examined in fish. In marine teleosts, the osmolality and ion concentration of the ingested seawater (SW) must be lowered before water absorption is initiated. By assuming that these processes are related to fluid transit, it is likely that alterations in these processes as well as in the water-electrolyte balance (WEB) of the animal would result with changes in the transit of intraluminal fluid. I hypothesized that marine teleosts regulate gut motility to achieve essential water absorption and thereby maintain the WEB. To test this, the gut of a marine teleost, the buffalo sculpin (Enophrys bison G.), was challenged in situ with forced drinking (continuous perfusion) at rates above and below that of the measured drinking rate (DR). Initially, the sensitivity of the WEB of the sculpin to preparatory manipulations that were essential for testing the above proposal was determined. The WEB was monitored before, during and after manipulation that included handling, containment, benzocaine-induced anesthesia, arterial and esophageal cannulation and serial sampling of blood. To monitor the WEB, indicators of the osmotic status and the intravascular volume were measured. Within one to three hours after surgery, a hyper-osmotic hemodilution resulted from an influx of hyper-osmotic fluid. Blood volume increased about 18% after surgery. The osmotic imbalance was corrected within 24 hours after surgery, whereas, the volume disturbance persisted. The occurrence of plasma hyper-osmolality after surgery was inhibited with esophageal occlusion. This implicated the gut as the origin of the osmotic and volume disturbances. Further data evaluation suggested that the surgery-induced WEB disturbance was a resultant of enhanced ion and water absorption in the upper and lower gut. Next, the DR and drinking behavior of the buffalo sculpin were determined. Also assessed was the influence of the manner of SW ingestion (ab libitum drinking or forced drinking) and of the rate of ingestion on SW modification by the gut. DR was variable within as well as among experimental groups. DR appeared to increase with the animal's capture duration suggesting that water permeability of the sculpin was gradually increasing after capture. The fluid volume and resident duration, and water modification in the upper gut and lower gut were consistent over a broad range of DRs. This demonstrated that the sculpin were ingesting SW frequently, perhaps in a manner similar to sipping. In respect to estimates made in sculpin allowed to drink ab libitum, forced drinking had a negative effect on desalting. Finally, a relationship was looked for between gut motility and the WEB of the sculpin. Several indicators of gut motility, water absorption, and the WEB were monitored while the gut was perfused at several different rates. If gut motility is regulated to achieve essential water absorption, then changes in gut motility would result in response to alterations in the forced drinking rate, so that adequate water modification and absorption would be accomplished and the WEB maintained. Over the levels of perfusion administered, the WEB was not maintained. With the elevation in perfusion rate, the intravascular volume increased and yet intestinal water absorption was maintained or gradually increased. It appears that under the circumstance of enhanced SW ingestion, the mechanisms regulating gut motility and water absorption are not integrated with mechanisms maintaining the WEB of the buffalo sculpin. It remains unclear if, without SW ingestion, gut motility and the WEB are actively related. / Graduation date: 1982

The directionality and consistency of evolution has long been a subject of contention among evolutionary biologists since the days of Darwin. However, it is unknown how much can be quantified and how much results from more complex variables. It is also unknown whether evolution is consistent or whether it occurs differently in each system. My study focuses on predation and habitat as ecological gradients that may create convergent evolution in livebearing fishes. In Chapter I, I focus on predation as a mechanism for driving convergent evolution in Gambusia affinis. A suite of 7 microsatellite markers was used in order to determine independence of morphological evolution. Mantel tests were used to compare genetic, phenotypic, geographical and environmental distances among the six focal populations. These tests showed that there was a significant correlation between genetic and geographic distance but no significant correlation between genetic and phenotypic distances, which may indicate that phenotypic divergence has arisen independently in multiple instances. The second chapter focuses on a unique form of convergence that arose during speciation of three livebearing fishes, which we termed "convergent speciation." I focus on habitat type as a selective pressure in the lake system of Lake Catemaco, Mexico and the surrounding rivers. Lake Catemaco has been isolated from the surrounding rivers for approximately 1.2 million years and during that time several endemic species have evolved in the lake. This provides an excellent study system for studying convergent divergence. To test the theory of convergent speciation in this system, a MANOVA was conducted. The effect of habitat was an important source of variance in the system, indicating that habitat is a likely driving force responsible for convergent speciation in the system. Using discriminant functions I was able to correctly predict the habitat of fish of six different species between 68% and 71% of the time. This may indicate that evolutionary response to habitat is consistent across taxa (i.e., convergent divergence is taking place).

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 2001. / Title from PDF title page (viewed Apr. 2, 2005). Vita. Includes bibliographical references (p. 127-141).

Thesis (Ph. D.)--University of Alberta, 2009. / Title from pdf file main screen (viewed on Dec. 21, 2009). "A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Physiology, Cell Biology and Developmental Biology, Department of Biological Sciences, University of Alberta." Includes bibliographical references.

Thèse de doctorat : Zoologie : Faculté des sciences de Paris : 1847. / Titre provenant de l'écran-titre.

Thesis (Ph. D.)--University of Michigan, 1926. / Cover title. Thesis note on label mounted on p. 427. Letterpress on versos facing the plates. "Reprinted from the Journal of Morphology and Physiology, vol. 43. no. 2, March, 1927." Bibliography: p. 478-480.