Ph.D. (Zoology) / Please refer to full text to view abstract

The aim of this study was to explore the karyology of temperate southern African barbine species in order to determine the extent and significance of polyploidy within the species. The study presents an optimised in vivo karyological protocol for the small barbines. The analysis of chromosomal data was explored using two approaches; measured (quantitative) and visual (qualitative). The karyology of 16 species of Barbus and six species of Pseudobarbus (Pisces: Cyprinidae) is reported. The study represents an almost complete (22/23 species) karyological survey of the temperate barbines. Chromosome number, arm numbers (NF) are recorded and karyotype morphology described for all species. Nucleolar organiser regions (NOR)s of 18 species have been examined by silver staining. Seven different AgNOR phenotypes occur among the species examined. Chromosome complements of the different species indicate at least three ploidy levels; diploid, tetraploid and hexaploid. Higher ploidy levels are represented in 78% (18/23) of species within the temperate fauna. This finding is remarkable, in the light of global proportions of cyprinid karyotypes, and provides an opportunity to shed further light on the evolution of polyploidy in barbine cyprinids. Results show that morphologically defined species complexes have distinct karyotypes, and most probably form cohesive phyletic clades. A phylogenetic tree was constructed using traditional morphological characters and tested against karyological data. The results suggests that similar ploidy states do not necessarily indicate close relationship between species. This supports a hypothesis of polyphyly for the African barbine cyprinids and also provides independent support for species complexes such as the "chubbyhead barb group" and the Pseudobarbus lineage. The broader implications of karyological findings are discussed within the context of African barbines and recommendations for further cytogenetic research are provided.

The social behaviour of a stream population of longnose dace, Rhinichthys cataractae dulcis, is described. Both males and females occupy the same riffle areas and defend territories (approx. 10 cm in diameter) during the breeding phase. In addition, male dace are evidently attracted to and interact agonistically with other males resulting in the formation of clusters of male territories. During the night, females leave their territories to court and spawn with territorial males. After spawning, males show strong nest site attachment and are inhibited from eating eggs. Parental males remain directly over the nest site and frequently probe the substrate with their snouts. They defend the area against all fish with the exception of receptive females with which they may spawn. Comparison with a stream population of the sub-species, R. cataractae cataractae, reveals differences in phenotypic appearance, diurnal rhythm of breeding activity, and female territoriality. Unlike R.c. dulcis, R.c. cataractae are reproductively active during daylight hours and males display bright nuptial coloration. Breeding coloration in males of R.c. dulcis is faint or absent. Unlike R.c. dulcis, males and females of R.c. cataractae are segregated into different habitats and females remain non-territorial. Experimental analyses of the physical and biotic factors involved in the causation of territorial behaviour were conducted in a laboratory stream tank. The major physical factor involved in the selection of territories by male dace is the presence of coarse gravel suitable for spawning. Female dace select and defend only enclosed areas which provide both overhead cover and shelter from current. Females prefer shelters which contain food and thus the presence of food may be a proximate factor involved in the selection of territories by female dace. Laboratory tests indicate that female territorial behaviour is elicited by interaction with breeding males. Outside the breeding phase, when territoriality is relaxed, male and female dace differ little in the areas they choose to occupy. The experimental evidence suggests that the functions of male territory are: i) provision of space in which males can court and spawn with females with minimal interference from other males, and ii) protection of eggs from intraspecific predation. For females, territoriality apparently functions to reduce conflicts with males (i.e., reduce courtship harassment and attacks from males). Changes in the behaviour of males occur after spawning and coincide with periods of greatest egg vulnerability. These post spawning behavioural activities of males protect freshly deposited eggs while making them less accessible to predators. The evidence also suggests that a major function of territory in both sexes is the provision of shelter from current. Dace not defending a shelter may be forced to make frequent movements in the strong current of the riffle habitat. Dace swimming against strong currents for even short periods (i.e., 5 min) become fatigued and lose their ability for coordinated locomotion. Such stressed individuals may be vulnerable to predation. The data also suggest that dace territorial behaviour may act as a dispersing mechanism, thereby limiting the density of breeding fish in a localized area. Territorial males of clustered groupings remain behaviourally synchronized. They display strong site attachment and interfere little with the reproductive activities of neighbouring males. Consequently, these social groupings function to further reduce interference from conspecifics. Assemblages of more widely spaced territorial males, created in the laboratory, experienced greater intraspecific interference and egg predation than did males of clustered territorial groupings. Thus it seems most probable that intraspecific interference and egg predation have provided a major selection pressure favouring both male territoriality and territory clustering in longnose dace. / Science, Faculty of / Zoology, Department of / Graduate

No description available.

Documentation of the seasonal feeding habits and ability to assimilate algae are presented for the first time for a North American grazing stream fish. The chiselmouth, Acrocheilus alutaceus, begins feeding on algal matter in early spring and has deposited large fat reserves prior to an early summer spawning season. A sharp decline in body fat content is then associated with a reduction in food intake at the onset of spawning. A subsequent increase in food intake, possibly with a higher energy value due to the inclusion of animal material, quickly restores fat reserves which then remain high through a period of almost exclusive herbivory (particularly on diatoms) in the late summer and fall. With the onset of winter, the diet of A. alutaceus shifts toward omnivory. Diatoms of the genera Cymbella, Gomphoneis, Synedra, and Melosira form the bulk of the diet. Both diatom and green algal food sources were assimilated by A. alutaceus, but at relatively low efficiency. The efficiency of assimilation of Ulothrix varied inversely with ration size, while the assimilation of diatoms was unaffected by ration size. Fiber was not assimilated. The protein fraction was assimilated more efficiently (44%) than total energy (33%). The order of preference evidenced in A. alutaceus feeding trials was: diatom > bluegreen > green > "mix" > moss. The ratio of digestible protein to digestible energy (P/E) in the food sources proved an excellent descriptor of observed preference. However, a linear combination of fiber content (as a negative factor) and gross P/E (as a positive factor) provided an analytically simpler descriptor and also predicted the correct order of preference. Chiselmouths apparently live much longer (22+ yrs) than was previously known (6 yrs). Formation of the opaque zone, generally recognized as indicating a growth period, is most evident on A. alutaceus otoliths from July through October. This coincides with the period of highest food intake and peak contribution of diatoms to the natural diet. / Graduation date: 1991

Thesis (Ph. D.)--Murdoch University, 1999. / Thesis submitted to the Division of Science. Includes bibliographical references (leaves 116-130).

Thesis (M.S.)--Marshall University, 2002. / Title from document title page. Document formatted into pages; contains viii, 59 p. illustrated with photos and maps. Bibliography p. 46-49.

Agricultural practices and increasing levels of pollution, water abstraction and numbers of predatory exotic fishes gave rise to mounting concern for the survival of the already endangered Twee River redfin, Barbus erubescens. Numbers were believed to be dwindling and an urgent re-assessment of the species' conservation status and major threats was called for. Distribution and estimated numbers of B. erubescens were detennined from a census conducted in the Twee River catclunent, and baseline knowledge of age and growth, reproduction, diet and habitat preferences was gained from biological work on collected specimens. Such understanding was necessary to formullate management ideas. Although an estimated 40% reduction in area of occupancy has occurred in the middle reaches of the Twee River system, the known distribution of B. erubescens was extended into the upper Suurvlei River. Despite fragmentation, surviving redfin populations remained healthy and total population size was estimated at 8400 individuals, 4100 of which were considered mature. Adults preferred pools with water exceeding 1 m in depth and tended to be associated with sandy or boulder substrates. Due to low numbers no such study was conducted on juveniles, although observations indicated a preference for the upper 50 cm of the water column, in or around marginal vegetation. Barbus erubescens spawn in summer and follow an asynchronous, iteroparous pattern. Males and females reach a maximum age of six years, maturing after two years at calculated SL of 45 mm in males and 42 mm in females. The diet was dominated by simulid and ephemeropteran larvae. Although the combined pressures of pesticide and fertiliser use, predation and competition from exotic species have undoubtedly had a negative impact on B. erubescens, the species has maintained viable populations. With continued expansion of these threats the focus of conservation attention may change but, at present, it is most likely agricultural water use, amounting to 7.43 x 10⁶ m³y⁻¹, 15% of the entire catchment production, which poses the greatest immediate threat to the survival of the species. Based on a deteriorating habitat and restricted area of occupancy, B. erubescens was rated Critically Endangered, and it is recommended that a conservation management plan be implemented in the Twee River catchment. The focus of such action should be on genetic preservation, with immediate projects including gamete cryopreservation and captive breeding and rearing programmes. Catchment management, including education and rehabilitation programmes, must be the long-term aim of conservation, to ensure the survival of B. erubescens.

Resumé: This study deals with the systematics and biogeography of a group of minnowlike Barbus species which, as adults, are characterized by bright red fins. The species are found in the coastal rivers of the fold belt region of the southern and south-western Cape Province. A closely related species, Oreodaimon quathlambae, inhabits certain high altitude streams of the Drakensberg mountains. Traditional methods were employed to revise the taxonomy of the species. Characters studied included morphometric and meristic measurements, and several qualitative anatomical features, several of which were studied in these species for the first time. A new species, Barbus erubescens Skelton, was described during the course of the study (Appendix 3). The taxonomic status of other species are endorsed or revised (B.afer and B.asper). Each species is redescribed and figured. The complete osteology of one redfin species, B.burchelli, is described and illustrated. Comparisons are made with all other redfin species and various osteological characters of systematic value are discussed. The phylogeny of the redfins is studied using Hennigian methods. Comparative data from other southern African Barbus species and pertinent literature were used to determine and evaluate synapomorphic characters and character sequences. The redfins sensu lato are shown to be diphyletic. Barbus calidus Barnard and B.erubescens were found to be sister species not closely related to the other redfin species. Oreodaimon quathlambae (Barnard) is shown to be monophyletic with the second redfin lineage. Barbus burgi Boulenger is placed as the plesiomorph sister species in this lineage and consecutive dichotomies derive Barbus burchelli (Smith); Barbus afer Peters, and Barbus asper Boulenger; Barbus phlegethon Barnard; Barbus tenuis Barnard and Oreodaimon quathlambae. The classification of the redfins is reviewed in the light of their phylogeny and recommendations for an infonnal hierarchy are made. The generic status of each lineage is considered and a new genus, Pseudobarbus, erected for all the redfin species except B.calidus and B.erubescens, but including O. quathlambae. The distributions of redfin species are recorded. A hypothesis is given to explain this distribution, based on a comparison of distribution patterns of a number of plant and animal species and a consideration of the geological and geographical history of southern Africa. Vicariance is suggested to be the major factor which influenced redfin distribution. A theory of dispersal explains the distribution of P.tenuis. The biogeography suggests the redfins are relatively ancient (possibly Miocene?) southern African fishes. Suggestions are made on future studies on the redfins. Attention is drawn to possible implications of the redfin study on systematic study of southern African freshwater fishes.

Sympatrically occuring Rhinichthys falcatus and R. cataractae were collected from four areas of the Fraser River drainage system. A life history examination of R. falcatus revealed that it is an omnivorous feeder, spawning in early July at age III and older, with some males of this age developing a permanent spawning color. Both sexes develop nuptial tubercles at age I. Females are heavier and longer than males, the greatest differences occuring at age III and older. Field collections from a variety of defined habitats showed that R. falcatus were most numerous during daylight in water velocities of less than 1.5 ft./sec. Adults occupied primarily depths of one foot or greater, the yearling and young-of-the-year fish were most numerous in depths of less than one foot. R. cataractae were most numerous during daylight in depths of less than one foot, the adults occupying water velocities of greater than 1.5 ft./sec, while yearling and young-of-the-year fish were distributed almost equally in velocities both greater and less than 1.5 ft./sec. Both species remained unchanged in their current distribution after dark but some young-of-the-year and yearling fish of both species moved offshore to areas deeper than one foot while adult R. falcatus became more numerous at night in onshore shallows of less than one foot in depth. Field observations on current distribution of both species were confirmed in laboratory current preference experiments in a stream tank. The preference of three size groups of both species for areas of little or no current and areas of either 1, 2, 3, or 4 ft./sec. water velocity in the stream tank were tested In 30 experiments. In all experiments but one, there was a significant difference between the ratio of R. falcatus to R. cataractae in the current areas; R. cataractae were more numerous. Morphology and function of the airbladder of both species were analysed, and differences in volume were explained on the basis of diverging habitat selection of yearling and adult fish. The habitat divergence between yearling and older R. falcatus and R. cataractae is in accordance with Gause's contention. / Science, Faculty of / Zoology, Department of / Graduate