Thesis (Ph.D.)--McMaster University, 2005. / Advisor: Colin A. Nurse. Includes bibliographical references (leaves 175-194). Also available online.

Acid-base regulation is vital for animals and while the inorganic carbon system largely determines body fluid pH, another potentially valuable acid-base pair is ammonia (NH4+/NH3). This study focuses on the American horseshoe crab (Limulus polyphemus), a phylogenetically ancient marine chelicerate with no published studies on its acid-base physiology. Physiological and molecular analyses indicate that Na+/K+-ATPase, Rhesus-protein (Rh), and carbonic anhydrase (CA) are involved in acid-base homeostasis and/or ammonia regulation. This likely occurs in the book gills, which consist of ultrastructurally distinct regions. The ventral half-lamella is ion-leaky and displayed high Rh-protein, cytoplasmic CA, and hyperpolarization-activated cyclic nucleotide-gated K+ channel mRNA expression levels, suggesting a specialization in facilitated CO2 and/or ammonia diffusion compared to the dorsal half-lamella. During hypercapnia acclimation, hemolymph acid-base status exhibited a compensated respiratory acidosis accompanied with signs of metabolic depression. Ammonia influx associated with high environmental ammonia acclimation was successfully counteracted, but induced modifications in acid-base homeostasis. / October 2016

Calcium ion has diverse beneficial roles in living organisms. Failure in Ca2+ homeostasis affects a variety of molecular and cellular processes, ultimately leading to many pathological consequences. In mammals, body Ca2+ homeostasis is maintained by the coordinated calcium (re)absorption that occurs in the small intestines, kidneys and bones, and is under tight hormonal control. In fish, two special organs, Corpuscles of Stannius (CS) glands and gills form a regulatory circuit to detect and regulate blood Ca2+ homeostasis. However, the underlying molecular mechanism in the regulation of gill Ca2+ uptake has not been fully examined. Moreover, some putative biological active substances in CS glands have not been identified. To address these research questions, a euryhaline fish, Japanese eel (Anguilla japonica) was used as an animal model for the study. Fish gill is equipped with epithelial calcium channel (ECaCl) as gatekeeper of Ca2+ entry, and membrane Ca2+-ATPase (PMCA) for Ca2+ efflux. To test if branchial ECaCl and PMCA responded to change in water Ca2+ level, we investigated the changes in fish adapted in artificial freshwater (AFW), Ca2+-deficient AFW (D-AFW) or high Ca2+-AFW (H-AFW). Our data illustrated both short-term and long-term effects on modulations of the transporters. The changes correlated with expression levels of stanniocalcin-1 (STC-1) in CS glands. This part of study supports the regulatory circuit between gills and the glands. In primary cell culture of Japanese eel gill cells, Ca2+ sensing was shown to be mediated by Ca2+ sensing receptor (CaSR) coupled to phospholipase C (PLC)-extracellular signal-regulated kinase (ERK) and PLC-inositol triphosphate (IP3)-Ca2+/calmodulin-dependent protein kinase-II (CaMK-II) pathways. And CaSR-STC-1/cyclo-oxygenase-2 (COX-2) mediated protective pathway in gill cells that exerts a possible protective mechanism against an increase in intracellular Ca2+ levels associated with transepithelial Ca2+ transport. Apparently, the protective effects against Ca2+-mediated cytotoxicity of gill cell were mediated by STC-1 binding on gill cells that led to elevations of cytosolic cAMP. In a follow-up experiment of using Ca2+-imaging system in a model of thapsigargin (TG)-induced elevation of cytosolic Ca2+, a hypocalcemic action of STC-1 was demonstrated and was found to be mediated by cAMP and COX-2 pathway. To further determine the gene expressed in CS gland responsive to changes in water salinity, the first transcriptome database of CS glands from fish adapted in freshwater or seawater condition. A de novo assembly of RNA sequencing data generated 11747 unigenes and revealed 475 genes that were differentially expressed. Three functional clusters: (1) Ca2+-metabolism, (2) blood pressure and (3) ion-osmoregulation were revealed. Gene targets, in addition to STC-1 in related to the regulation of calcium metabolism and blood pressure, like calcitonin, atrial natriuretic peptide-converting enzyme and endothelin-converting enzyme 1 were identified. Taken together this thesis described a comprehensive study on the functional circuit between gills and CS glands to decipher the regulation and functions of transporters and hormones in calcium metabolism in fish.

A method has been developed for the continuous automated monitoring of cardiac output in adult rainbow trout. Average cardiac output measured under control conditions and varied environmental conditions of hypoxia and post-hypoxia was significantly higher (P≤ 0.05) in male than female trout. The cardiac output of trout in spawning condition was significantly higher (P≤ 0.05) than that of trout not in spawning condition. Measurements of pulsatile cardiac output were made simultaneously with trout ventilation, and revealed ventilatory interactions with blood flow that varied depending on environmental oxygen condition. The method for monitoring gill blood flow was used with methods for automated measurement of gill water flow, oxygen uptake, and chemical flux in vivo. An experimental protocol was developed in which environmental oxygen was varied to obtain maximum increases in water flow over the gills without blood flow changes, and subsequent attainment of maximum increases in blood flow through the gills with decreasing water flow. The protocol was used as a probe to study variations in chemical flux with varied blood or water flow. The changes in gill flux of butanol (Log octanol/water partition coefficient (P) = 0.88) measured during control, hypoxia, and post-hypoxia correlated with observed changes in blood flow. A 70% increase in butanol flux was noted with a 50% increase in cardiac output, but there was no increase in butanol flux with a 100% increase in ventilation volume. Changes observed in the gill flux of decanol (Log P = 4.57) measured under varied environmental oxygen conditions correlated with observed changes in ventilation volume. A 100% increase in decanol flux was noted with a 160% increase in ventilation volume. The observed blood flow limitations to uptake of the low Log P butanol, and the water flow limitations to uptake of the high Log P decanol helped to verify assumptions made in recently proposed flow-limited models for prediction of chemical flux across fish gills. / Graduation date: 1991

published_or_final_version / Zoology / Master / Master of Philosophy

No description available.

Macome secta has been reported along the western coast of North America from the Aleution Islands to Lower California (Packard, 1918), Indicating adaptation to a wide range of habitats. In the Dillon Beach ares, Racons secta is found in a well protected cover just inside. and to the cast of the mouth of Tomales Bay. All specimens collected for this project wore takan from one site on a mudflat near Lesson's Landing, approximately one mile south of the Pacific Marine Station, Dillon Beach California. The exact location of the collection site on the mudflat may be seen in the serial photographs (Fig. 1 and 2).

No description available.

No description available.

No description available.