No description available.

Data collected from the 16 species of the fish family Cyprinidae (Pisces: Teleosti) found in Britain were examined morphometrically and electrophoretically to examine the taxonomic relationships within the group and aspects of the occurrence and identification of interspecies hybrids. The analysis of morphological characters by Principal Components Analysis was not able to separate the morphological characters into clear character suites. A rooted dendrogram using Gower (1971) mixed data coefficient and UPGMA was found not to correlate strongly with the presently accepted classification or with the subsequently produced phenogram based upon the enzymatic results. The phenetic treatment of electrophoretic results gave a consensus topology equivalent to Nei's (1972) .D. and UPGMA with standard errors. Several taxonomic changes were suggested, the reduction from six to two sub-families and moving two species into different genera, Blicca bjoerkna to become Abramis bjoerkna and Alburnus alburnus to become Leuciscus leuciscus. The use of electrophoretic characters in preference to morphological ones was strongly validated. Discriminant Function Analysis could not discriminate between populations with and those without hybrids. An unidentified specimen from the River Trent, Nottingham, was also described. It was found enzymatically not to correspond to any of the 16 species examined, but could be placed in the classification in the sub-family Leuciscinae and Abramin lineage.

No description available.

No description available.

No description available.

Chapter 1 - General Introduction. Part I reviews the structure and function of fish muscle, including fibre orientation, the properties of different muscle fibre types and the recruitment of muscle fibres during swimming. Part II concerns the effects of acute temperature changes on fish muscle and describes a variety of mechanisms underlying temperature adaptation, with particular emphasis on the mechanical performance of fish muscle. Chapter 2 - Temperature and the mechanical properties of live muscle fibres from the teleost Myoxocephalus scorpius. Small bundles of fast fibres were isolated from the myotomal muscle of the teleost Myoxocephalus scorpius. The temperature dependence of isometric contractile properties and the force-velocity (P-V) relation were studied. Fibres were found to deteriorate above 18°, and the force plateau during tetanic stimulation was not maintained above 15°. Twitch and tetanic tension (Po) showed optima at around 8°. Force-velocity curves were fitted using either Hill's hyperbolic equation or a hyperbolic-linear (hyp-lin) equation. The best fit to the data was provided by the hyp-1in equation, which gave consistently higher values for unloaded contraction velocity (Vmax): 4.3, 8.1 and 9.5 muscle lengths s-1 at °, 8°, and 12° respectively. Both isometric and isotonic data from live fibres was compared with skinned fibres and live fibres from other vertebrates. The P-V relation was found to become progressively more curved at higher temperatures. Muscle power output calculated from the hyp-lin equation was 124 Wkg-1 at ° and 256 Wkg-1 at 8°. Curves normalised for Po and Vmax at each temperature show that the change in curvature is sufficient to increase the relative power output of the muscle by around 15% on decreasing the temperature from 8° to °. Chapter 3 - The myology of the pectoral fin of the common carp Cyprinus carpio L. and variation in fibre composition with temperature acclimation. Common carp (Cyprinus carpio L.) were acclimated to either 8° or 20° for 8 weeks (12h light:12h dark). The myology and skeletal structure of the pectoral assemblage of the carp was studied. Cross-sections of the entire assemblage were taken for histochemistry in order to determine the distribution of fibre types within the musculature. Examination of the fibre diameter range data reveals a larger number of smaller slow fibres in the muscle of 8° C-acclimated fish, commensurate with a hypothesis that the slow fibre mass is proliferating during cold-acclimation by producing new slow fibres. Chapter 4 - Temperature acclimation in the common carp: force-velocity characteristics and myosin subunit composition of slow muscle fibres. Common carp were acclimated to either 8° or 20° for 6-12 weeks (12h light:12h dark). Bundles of 20-50 fibres were isolated from the superficial region of the pectoral fin abductor superficialis muscle. Histochemical studies showed preparations to contain 93-100% slow muscle fibres. The maximum tetanic tension (Po) produced by fibre bundles was similar when measured at the acclimation temperature of each group. Chapter 5 - General Discussion The results detailed in this thesis are discussed in relation to the effects of temperature on fish swimming. Recent developments in technique are described and some suggestions for further work using these techniques are outlined.

The structure of the autonomic innervation of the gastro-intestinal tract and heart of a number of teleosts was examined using light and electron microscopy and fluorescence histochemistiy. In the scorpion fish, the structure of the coeliac ganglion and the distribution of aminergic neurones in the brain was also investigated. The distribution of monoamine-containing nerves in the gut of scorpion fish, plaice, herring and ice fish was described using fluorescence histochemistry. Castecholaminergic fibres are found in the myenteric plexus and in the submucosa where they frequently run with blood vessels. They also supply the longitudinal muscle of the rectum and are often prominent in the circular muscle of the pyloric and anal sphincters. Serotonergic nerves pass through the submucosa to the subepithelial plexus and 5HT can be isolated chromatographically from gut wall homogenates. Serotonergic enterochromaffin cells are present in the stomach and distal rectum and in the herring a catecholamine-containing form was observed in the pyloric stomach. Ultrastructurally two types of axonal profiles are seen in the gut. The first contains small agranular vesicles typical of cholinergic nerves and these synapse with the perikarya of myenteric neurones, while the second contains a mixture of large and small granular vesicles and though often found adjacent to ganglion and muscle cells is not involved in conventional synapses. Both types are present in the subepithelial plexus. Histochemical and drug depletion studies suggest that some of the granular vesicles contain biogenic amines. The hearts of plaice, dab and angler fish do not contain adrenergic nerves Taut these were found in all other species examined. In the lingcod, aminergic perikarya are also present in the cardiac ganglion. With the electron microscope, the densest innervation of cardiac muscle was found close to the cardiac ganglion but though fluorescent nerves are abundant, nerve profiles contain predominantly agranular vesicles. The coeliac ganglion of scorpion fish is similar in structure to sympathetic ganglia in other vertebrates. It contains two types of principal cell as well as a population of small intensely fluorescent (SIP) cells. The SIP cells appear to become more numerous in early summer when vesicles in the equivalent cells observed ultrastructurally develop electron dense granules. The catecholaminergic and serotonergic structures in the brain of scorpion fish were described and compared to those of other teleosts and higher vertebrates.

Halichoeres socialis Randall & Lobel, 2003, is the only wrasse species (Teleostei: Labridae) with a restricted distribution within the Caribbean Meso-American Barrier Reef (MABR), Central America. This study examined the early life history of H. socialis to gain insight into its natural history and to assess if any pattern in otolith microstructure could be linked to its endemism. The sagittal otoliths from 67 individuals (ranging 9.8–43.4mm SL) were analyzed to determine the daily age and increment profile. Results indicate that (1) H. socialis displays a typical “settlement mark”; (2) the pelagic larval duration (PLD) ranged from 22 to 32 (mean=27, n=59) days, which was similar to its congeners; and (3) the juvenile growth rate is 0.7mm/d, which was faster than most congeners. The endemism of H. socialis is not explained by its PLD. Alternatively, it is possible that larval behaviors (vertical migration and/or schooling) play a key factor in how H. socialis larvae are retained within the MABR region. / 2026-03-19T00:00:00Z

Sperm competition is a widely-recognized and powerful selective force. Male accessory glands are organs found across animal taxa that can influence sperm performance, and thus may be selected for in competitive contexts. In fishes, these organs are in fact rare, but display great diversity in form and function across species. Although the accessory gland is known to play a role in mate attraction, parental care, fertilization, or post-copulatory competition in a few select species, the role of this organ remains a mystery in most species. Many fishes with accessory glands also exhibit alternative reproductive tactics (ARTs), which add an extra layer of complexity to how species respond to sperm competition. Because males of different ARTs typically experience different levels of sperm competition risk, it’s possible they may differentially invest in accessory glands to overcome this competition. In this thesis, I used the plainfin midshipman fish (Porichthys notatus), a species with both ARTs and an accessory gland, to experimentally investigate the role of the accessory gland in sperm competition and uncover how this organ may differ between ARTs. Over a two-year period, I studied tactic-specific investment in the accessory gland in fish from the beaches of British Columbia. I also examined the effects of seminal fluid, produced in part by the accessory gland, on sperm performance and morphology. I found that males adopting the ‘guarder’ male tactic invested more in one region (the lobules) of this organ, while males adopting the smaller ‘sneaker’ male tactic invested more the other region of the gland (the nodes). Using data collected over five years, I found that guarder males also invested more in their whole accessory glands. Additionally, I report that sperm swam faster in the presence of seminal fluid, and seminal fluid increased sperm head size in both male tactics and increased midpiece size in guarder males. These results suggest that the plainfin midshipman accessory gland may have dual functions, one of which may be to aid sperm competitive ability through enhancements in swimming speed and potentially more successful sperm morphology. Taken together, the results of my thesis improve our knowledge of the role of non-sperm components like seminal fluid and the accessory gland in sperm competition, and demonstrate how species with ARTs can have varying physiological responses to such competition. Only a handful of studies have considered the effects of seminal fluid on sperm performance. By examining sperm competition in a more biologically relevant way and incorporating the effects of a little-studied organ that impacts sperm competition, we should be able to more generally and accurately appreciate the dynamics of post-copulatory competition and fertilization. / Thesis / Master of Science (MSc)

No description available.