A cladistic analysis of interrelationships for 53 (of 58) pleuronectid (Order Pleuronectiformes) species was performed using 106 morphologial and osteological characters. The analysis resulted in a 50% majority-rule consensus tree of 128 equally parsimonious cladograms (heuristic search, 403 steps, ci = 0.33, ri = 0.79). Only five of 47 resolved nodes were observed in less than 100% of the cladograms. These five nodes are restricted to interrelationships within one subfamily. The Pleuronectidae (sensu Chapleau and Keast, 1988) are monophyletic based on ten synapomorphies. In addition, five subfamilies were defined Hippoglossinae, Eopsettinae, Lyonsettinae, Hippoglossoidinae and Pleuronectinae. The largest subfamily, the Pleuronectinae, was further subdivided into four tribes. Psettichyini, Isopsettini, Microstomini and Pleuronectini. The interrelationships established within Pleuronectidae provide a strong foundation for a simplified yet phylogenetically informative taxonomic nomenclature. The genera Atherestes and Reinhardtius; Embassichthys, Errex, Glyptocephalus, Tanakius and Microstomus; Hypsopsetta and Pleuronichthys are regrouped in Reinhardtus; Microstomus and Pleuronichthys, respectively. To preserve the monophyletic status of Eopsetta, E. exilis was reassigned to the genus Lyopsetta (Lyopsettinae). The genus Pleuronectes (as defined by Sakamoto, 1984a) is polyphyletic. It now includes only five species: Pleuronectes glacialis, P. pinnifasciatus, P. platessa, P. putnami and P. quadrituberculatus. Other Pleuronectes species are reclassified in Isopsetta, Limanda, Parophrys, Platichthys, Psettichys, and Pseudopleuronectes. The monophyletic status of the genus Limanda (six species) is uncertain based on unresolved relationships between these species and other taxa in the tribe Pleuronectini.

In the North American eel, Anguilla rostrata, the problems of intracellular location of isocitrate oxidation and the control of the tricarboxylic acid (TCA) cycle in the liver were investigated. Three methods were used to elucidate these problems. The first method involved the determination of isolated mitochondrial oxidative capacity with different TCA cycle intermediates measured by the Clark oxygen electrode; isocitrate was oxidized at a rate comparable to the subsequent TCA cycle intermediates (∝ ketoglutarate, succinate and malate) showing that these isolated particles are able to maintain isocitrate oxidation. However, pyruvate oxidative rate was significantly lower than isocitrate, and citrate and acetate were not oxidized alone or in conjunction with malate or oxaloacetate. The second method dealt with the incorporation of a radioactive substrate into the isolated mitochondria and the analysis of the distribution of this label in the TCA cycle intermediates. Labelled citrate was used with added aconitase. Results demonstrated that isocitrate was mobilized in the isolated mitochondria with label accumulation in the subsequent TCA cycle intermediates. This experiment suggested that isolated intact eel liver mitochondria contain all the enzymes necessary for the complete oxidation of isocitrate by the TCA cycle. The third method was the spectrophotometric and oxygen electrode analyses of specific activities and compartmentalization of enzymes necessary for the TCA cycle. Results demonstrated that citrate synthase (CS) and transhydrogenase activities were found only in the mitochondrial fraction; aconitase was detected only in the supernatant; and NADP-specific isocitrate dehydrogenase (NADP-IDH) and glutamate dehydrogenase (GDH) were measured in both fractions. NAD-IDH was not detected using a number of isolation procedures. Since CS and transhydrogenase activities were lower than those of NADP-IDH, these two enzymes probably limit metabolic flux through the TCA cycle in eel liver. From these data, a proposal for the physiological significance and the control mechanism of the TCA cycle in the eel liver is discussed, with isocitrate oxidation occurring either within the mitochondrial or cytoplasmic compartments depending upon the NADP/NADPH ratio and/or the energy status of the cell.

The limited ability of humans to decipher the signals produced by other animals has undermined our understanding of the level of communication they possess. Within the avian world, non-vocal sounds have frequently been suggested, as possible forms of communication, but to date have not been tested. Previous studies of hummingbird wing sounds and wing beat frequencies have been limited by technological capabilities and/or sampling effort and have subsequently produced incomplete results. Despite this, several studies have used these questionable results to calculate such things as the relationship between wing length and wing beat frequency. In the absence of a firm understanding of the variability of wing beat frequency within and between individuals of each sex, these studies are subject to an unknown degree of error. Chapter one comprehensively documents the wing sounds of four hummingbird species that breed in Canada. Additionally, I document wing trill characteristics, a new interaction behaviour involving an increase in wing beat frequency and the first account of a wing trill in a female hummingbird. In chapter two, supported by the findings of chapter one, I investigate the role of these non-vocal sounds in intra- and inter-species communication by using wing sounds as playback stimuli. The later chapter's positive communication findings open the door to the field of non-vocal hummingbird communication and beyond into the use of non-vocal communication signals in other avian species.

The genus Cyclopsetta Gill, 1889 was reviewed and four species were recognised: C. chittendeni Bean, 1895 and C. fimbriata (Goode and Bean 1886) from the Atlantic coast of North and South America including Gulf of Mexico and the Caribbean Sea; C. panamensis (Steindachner 1875) and C. querna (Jordan and Bollman 1890) from the Pacific coast of North and South America. A first cladistic analysis of Cyclopsetta and Syacium was conducted at the species level using morphological data. The result showed that each genus is monophyletic. Cyclopsetta is divided into two subgenera: Cyclopsetta comprises C. chittendeni and C. fimbriata and Azevia comprises C. panamensis and C. querna. Syacium longidorsale is the first species to branch off the ancestor followed, subsequently, by S. ovale, S. gunteri and S. maculiferum. S. latifrons and S. papillosum are sister species which together form a trichotomy with S. guineensis and S. micrurum.

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