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Threespine sticklebacks (Gasterosteus aculeatus) inhabit both marine and freshwater environments along the Pacific coast of North America, In this study, sticklebacks collected from 73 locations on Vancouver Island, the Sechelt Peninsula and the lower Fraser River Valley of British Columbia, and six sites in northwestern Washington State, were assayed by starch gel electrophoresis in order to examine relationships among and between marine (trachurus) and freshwater (leiurus) populations. Six enzymes, coded for by eight genetic loci, were examined. Of these, two aere monomorphic for the same allele in all populations, the remainder were polymorphic to varying degrees. Laboratory breeding studies employing both marine and freshwater fish as parents confirmed the genetic interpretation of observed variability in isozyme banding patterns. One of the monomorphic enzytaes, isocitrate dehydrogenase, exhibited a sexually dimorphic isozyme pattern. Levels of polymorphism and heterozygosity were slightly higher than average, bat within the range of those characterizing other vertebrate species. In general, genotypic ratios conformed to Hardy-Heinberg expectations, and allele frequencies within populations did not shift over short time periods. Gene frequencies did not vary among sticklebacks of different sizes nor among those caught by different methods from the same population. Gene frequencies at all polymorphic loci were significantly heterogeneous among stickleback populations. Average frequencies at two loci (Pgm and Mdh-3) differed significantly between marine and freshwater fish. In addition, average frequencies at two other loci (Mdh-1 and Ck) were different among sticklebacks inhabiting different types of freshwater environments. Among freshwater populations the Ck ⁸⁵ and Pgm ⁹⁰ alleles displayed clinal geographic variability in frequency, possibly as a result of the differential sampling of various freshwater habitat types in different regions. Allele frequencies at three loci (Pgm, Ck and Pgi-2) differed between marine sticklebacks collected from the Strait of Georgia and those from waters off the vest coast of Vancouver Island. Calculation of Nei’s genetic distance indicated that while marine populations are relatively homogeneous at electrophoretic loci, freshwater populations are highly heterogeneous. The average genetic distance between marine and freshwater populations was similar to that separating pairs of freshwater populations. The genetic distance between freshwater populations was greater between than within watersheds, but allele distributions at individual loci did not differ significantly between two watersheds levels of polymorphism and heterozygosity were relatively high in populations from the ocean, large lakes and low-lying streams, and low in those from small lakes and isolated streams. Both deterministic (natural selection) and stochastic (founder effects and genetic drift) mechanisms can be invoked to explain these patterns. Morphologically and ecologically distinct benthic and limnetic sticklebacks within single lakes, and freshwater and marine sticklebacks within a stream, constituted genetically discrete populations. There was a striking congruence in the patterns of morphological and electrophoretic variability among the populations comprising such 'species pairs'. The results of this study are compatible with the suggestion that freshwater populations of the study area are polyphyletic, and have arisen independently from marine sticklebacks which invaded the region since the last ice age, about 10,000 years ago. / Science, Faculty of / Zoology, Department of / Graduate

The present study was undertaken to investigate colour and sex determination mechanisms through the application of androgenesis, gynogenesis and controlled breeding programme with the objective of producing all red males in 0. niloticus. The highest yield of androgenetic haploid to pigmentation stage was 24.6±3.5% (relative to controls) with optimal UV irradiation dose of 450Jm"2 for 5 minutes. The highest survival rate of diploid androgens was 0.07±0.07% (relative to controls) to yolk sac stage using a heat shock of 42.5°C for 3 minutes 30 seconds applied at 25 minutes after fertilisation. All paternal inheritance of diploid androgenetic tilapia was verified using DNA fingerprinting. The mean recombination frequency of the red skin colour gene in meiotic gynogens was 0.12±0.04. All maternal inheritance of meiotic gynogens was verified using the isozyme locus ADA*. Analyses of sex ratios of meiotic gynogens suggested that male progenies were produced by an epistatic sex determining locus (SDL-2 with two alleles SR and sr) causing female to male sex reversal in the homozygous phase (srsr) but with limited penetrance. A close linkage was found between a sex determining locus (SDL-2) and the red gene. No significant difference was found between colour genotypes (namely homozygous red, heterozygous red and wild type) in terms of total fecundity, ISI (inter spawning interval), egg size and survival rate. Overall mean ISI was 26.3±1.0 days. Mean total fecundity was 1096 eggs. Fecundity varied over successive spawns but this variation did not appear to be related to spawning periodicity. Hormonal and thermal feminisation were compared on all YY male progeny of 0. niloticus. While similar female percentages of 32.0±5.2 and 33.8±1.5% were produced, significantly higher intersex percentages of 18.5±2.5 and 1.6±0.8 were observed in heat and DES treated groups, respectively. Heat treatment groups showed the lowest survival rate of 62.6±9.8% compared to the survival rates of 97.0±0.9% and 97.3±0.8% in controls and DES treated groups, respectively. YYRR males and YYRR neofemales were produced by integrating existing YYrr males and YYrr neofemales from the Egypt-Swansea-Philippine isolate and YYRR androgenetic males from the Stirling isolate with XXRR females and XYRR males of the Stirling isolate of Egyptian strain 0. niloticus. In summary, this study provides valuable information regarding the colour and sex determination mechanisms of 0. niloticus. The research in this thesis also demonstrated that both YY genotype and red coloration can be combined in a single strain in order to produce all male and stable red coloured 0. niloticus.

Genetic differentiation among juvenile samples of the European seabass (Dicentrarchus labrax) from the coast of Portugal is reported by means of two types of genetic markers: allozymes and microsatellites. Repeat samples were taken from 5 different nursery grounds (Aveiro, Foz, Obidos, Milfontes and Faro) along the coast of Portugal between November 1992 and February 1994. Starch-gel electrophoresis was used to assess the level and distribution of genetic variability of 38 loci. Six of these were found to be polymorphic at the 99% level and were used in population surveys: AAT-3*, ADA *, GPI-I *, GPI-2*, G3PDH-2*, SOD*. Statistical analysis revealed low but statistically significant multilocus F.'I (0.0108, p<O.OOI) values suggesting that population structuring exists along the Portuguese coast line. The results indicate that there is some restriction in gene flow between the more southerly population at Faro and all other sites to the North. Five microsatellite loci were screened in over 300 individuals. High levels of polymorphism (number of alleles observed per locus ranged from 20 to 41) and observed heterozygosities, ranging from 0.45 to 0.89 (mean over all loci = 0.71) were detected. Two loci displayed heterozygosity deficits (Dla6 and Labrax-9) and were not used in population comparisons. Statistical analysis revealed low but statistically significant multilocus FST (0.0025, p<O.OOl) at the other three loci (Dlall, Labrax-3 and Labrax-8). No clear geographic patterns emerged from these results. Overall allozymes performed well when compared to microsatellites, in detecting microgeographic genetic structure in this species. Microsatellites revealed high levels of polymorphism that should prove useful as markers in the management of wild and farmed seabass stocks in the future. The level of differentiation, low values of F ST , detected among the sites is low but is typical of marine species which have a much greater chance of mixing.

The thesis consists of four papers that deal with the development of a biologically reasonable role for protein alleles in fisheries management. Paper 1: The need for an understanding of the biological properties of protein alleles is established by arguments that the neutral theory of alleliccvariation is an effective null hypothesis to the Fisher/Haldane/Wright definition of selection, but not a legitimate explanation for allelic variation in its own right. The literature demonstrating physiological differences between alleles in fish is reviewed. General biochemical and various ecological arguments are put forward to support the empirical evidence for significant physiological differences between alleles. The three main empirical arguments of neutral theorists, the segregational load argument, the molecular clock analogy, and the correlation between polymorphism and the molecular weight of proteins, have had a great influence on practical analysis and experimental design of fisheries management experiments in allele frequency. The validity of these empirical arguments is questioned. Statistical problems associated with the neutralist usage of allelic variation in fisheries management are briefly reviewed. Paper 2: Transferrin alleles are widely used in fisheries management as neutral markers. The biological role of transferrin alleles is reviewed and the effects of the biological properties and the statistical use of transferrin variants are discussed. Paper 3: The biological role of alleles requires some relationship between allelic variants and the parameters of fisheries management models before allelic variation can be assigned a practical role in fisheries management. Such a relationship is demonstrated between allelic genotypes at the phosphoglucomutase locus in liver and growth in the fish Cheilodactylus macropterus. Arguments are also presented for a significant change in allele frequency in this species due to fishing pressure. Paper 4: A biological role of alleles in fisheries management that is based on physiological differences between alleles may require an extensive understanding of the physiology and biochemistry of the fish before the allelic variation can be put to any practical use. Experimental data are presented to show that the metals Fe, Zn, P, Sr, and Na in the fish otolith reflect the ambient temperature. Thus an individual temperature life-history of a fish may be found in the otolith providing one, of the important experimental parameters necessary to understanding the biochemical and physiological role of allelic variants. The thesis concludes with a brief and general overview of fisheries management models and the reasons why the biological role of allelic variation is pertinent to these models. / Arts, Faculty of / Sociology, Department of / Graduate

The big-oui hybrid catfish (female C. macrocephalus x male C. gariepinus) was successfully achieved using artificial hybridization. This hybrid combines the superior taste of the C. macrocephalus with the faster growth rate and higher resistance to environmental conditions of the C. gariepinus and is now the biggest fresh-water aquaculture product in Thailand. In this thesis the results of experiments involving hybridization and genetic manipulation were used to investigate the nature of the hybridization event. This information was used to develop broodstock for Clarias catfish breeding programme. Allozyme studies resolved 18 protein loci encoding different enzyme systems in C. batrachus, C. macrocephalus, C. gariepinus and the big-oui hybrid. GPI-2*, MDH-2* and LDH-l* show clearly variation between the hybrid and the parental species and were used for species diagnostic loci. Comparisons of fertilisation and survival of the big-oui hybrid, reciprocal cross hybrid, F2 hybrid, back cross hybrid and their parental species were carried out. The only cross involving the F 1 big-oui hybrid still gave viable embryos and fry was between female F 1 hybrid and male C. gariepinus. The F2 hybrid never developed to hatch. Karyotyping studies showed a modal chromosome number of 2n=54 in C. macrocephalus; 2n=56 in C. gariepinus; 2n=55 in the big-oui hybrid, the reciprocal hybrid and the back cross hybrid. Using male C. gariepinus from two other stocks ('Malawee' and 'Wageningen') were carried out to produce the big-oui hybrid. Cold shock at 2°C administered for 15 mins duration and 4 mins after fertilisation was the most effective in inducing 100% triploidy in big-oui hybrid while heat and pressure shock were less effective. Growth performance of diploid and triploid hybrids was not significantly different. The triploid hybrid were shown to be functionally and endocrinologically sterile. Gynogenetic diploids were produced by fertilizing C. macrocephalus eggs with C. gariepinus sperm that had been genetically inactivated with ultraviolet (UV) light, and then cold shocking the eggs after fertilisation. The UV dose of 200 Il W cm -2 for 2 mins using a sperm concentration of 2.5 x 108 mrl was optimal in genetically inactivating sperm without seriously compromising motility. Cold shock at 2°C, started at 4 mins after fertilisation and 15 mins duration gave the maximum number of meiotic gynogenetic offspring. The parental contribution in the gynogenetic offspring was check by using the species diagnostic allozyme loci and showed no evidence of male contribution. Gynogenetic offspring were grown on to investigate the sex ratio. All gynogenetic offspring were female suggesting female homogamety in this species. The possible implications of the above results of hybridization and genetic manipulation studies in Clarias catfish culture are discussed.

by Henry, Kam-yin Cheung. / Thesis (M.Ph.)--Chinese University of Hong Kong, 1988. / Bibliography: leaves 119-126.

No description available.

published_or_final_version / Biochemistry / Doctoral / Doctor of Philosophy

Orientador: José Carlos Pansonato Alves / Banca: Orlando Moreira Filho / Banca: Patrícia Elda Sobrinho / Resumo: O mapeamento cromossômico de sítios de DNA repetitivo vem sendo realizado em vários estudos citogenéticos em peixes e tem permitido uma melhor caracterização da biodiversidade e evolução genômica da ictiofauna Neotropical. Dentre as diversas espécies de peixes distribuídas nesta importante área geográfica, podemos destacar o gênero Moenkhausia, um dos mais especiosos grupos de peixes da família Characidae. Do ponto de vista citogenético, este gênero demonstra variação do número diploide de 48 a 50 cromossomos, bem como a presença de microcromossomos B descritos para diferentes espécies/populações. No entanto, estudos citogenéticos de espécies de Moenkhausia coletadas em riachos de cabeceira da bacia Amazônica e bacia do Alto rio Paraguai ainda são incipientes, bem como os estudos relativos à distribuição de DNAs repetitivos nos genomas de diferentes espécies de Moenkhausia. Neste sentido, o presente trabalho teve como objetivo a caracterização cariotípica de Moenkhausia cosmops, M. cf. forestii, M. cf. nigromarginata, M. oligolepis e Moenkhausia sp. coletadas em diferentes rios e riachos de cabeceira da bacia Amazônica e bacia do Alto rio Paraguai. Todas as espécies foram analisadas através de técnicas citogenéticas clássicas (coloração com Giemsa, localização das RONs pela impregnação por Nitrato de Prata e bandamento C) e molecular (hibridação in situ fluorescente com sondas de DNAr 5S e 18S, histona H1, snDNA U2 e sequências teloméricas (TTAGGG)n). Todas as espécies/populações analisadas apresentaram 2n=50 cromossomos, porém com fórmulas cariotípicas distintas entre elas. O bandamento C revelou um padrão de bandas heterocromáticas similar entre essas espécies, exceto em M. cf. nigromarginata. A impregnação por Nitrato de Prata evidenciou Ag-RONs simples em todas as espécies analisadas. A FISH utilizando o DNAr 18S como sonda confirmou os resultados obtidos com o Nitrato de Prata e... / Abstract: The cytogenetic mapping of repetitive DNA has been applied in several studies in fish, which allowed a better characterization about the biodiversity and genomic evolution of Neotropical ichthyofauna. Among the several fish species living in this area, the genus Moenkhausia, one of the specious groups inside Characidae, is remarkable. From a cytogenetic point of view, this genus show variations in diploid numbers of 48 to 50 chromosomes, as well as the occurrence of B chromosomes in different species/populations. However, cytogenetic studies in Moenkhausia collected at different rivers from the Amazon and Upper Paraguay River basins are scarce, as well as studies investigating the chromosomal distribution of repetitive DNAs in different species. In this sense, the present study aimed to characterize the karyotypes of Moenkhausia cosmops, M. cf. forestii, M. cf. nigromarginata, M. oligolepis and Moenkhausia sp. collected at different sites in the Amazon and Upper Paraguay River basins. All species were analyzed using classical (conventional staining with Giemsa, localization of NORs by impregnation with Silver nitrate and C-banding) and molecular (fluorescent in situ hybridization with 5S and 18S rDNA, H1 histone, U2 snDNA and telomeric sequences (TTAGGG)n probes). All the herein analyzed species showed 2n=50 chromosomes, with different karyotype formulas. C-banding evidenced similar patterns of heterochromatin distribution in all species, except in M. cf. nigromarginata. Silver nitrate staining evidenced simple Ag-NORs in all species and FISH with 18S rDNA probes confirmed these results e revealed additional sites in M. oligolepis. The 5S rDNA was interstitially located in multiple sites in all species. Notably, both ribosomal sites were found in synteny in one population of M. oligolepis. The H1 histone sites were co-located in a single pair with 18S rDNA and the U2 snDNA was located at multiple sites in all species. Additionally, the ... / Mestre