Fecundity data were obtained for twelve species of British Columbia freshwater fishes by use of a displacement method. Data for an additional fourteen species were obtained from the literature. Fecundity relative to a unit body weight was considered superior to absolute fecundity for use in racial studies. Egg diameter was significantly larger in anterior than in posterior regions of ovaries from five species tested. Egg diameter was positively correlated with fork length within and between species. Amongst twenty-six freshwater species considered, egg diameter was found significantly correlated with reproductive characteristics. Fish with eggs of large mean diameter generally have amber to salmon colored eggs, non-adhesive eggs, long incubation periods, redd construction, stream spawning and variable spawning season. Fish with eggs of small mean diameter have white to yellow eggs, adhesive eggs, short incubation period, lack of redd construction, variable spawning location and spring or summer spawning season. / Science, Faculty of / Zoology, Department of / Graduate

Eggs of Pacific herring were exposed to air for different periods of time in simulation of tidal effects on spawn deposits at varying beach heights. The maximum exposure range was 2/3 of a 24 hour day corresponding roughly to the exposure of eggs at 4 meters above mean low tide on the British Columbia coast. Egg size, spawning fish length, and egg clump size were examined as secondary factors modifying the effect of exposure. Incubation time dropped from 19 to 18 days with only two 2-hour periods of exposure per day and thereafter fell slowly. It is suggested that oxygen deprivation triggered a hatching response for the initial drop, whereas the gradual decrease was due to a higher air temperature increasing metabolism. Hatching mortality rose steadily from an unexposed 13% to 31% at maximum exposure time, with significantly higher contributions from eggs of smaller fish and smaller egg clumps. Larval length at hatching for the unexposed eggs was 7.7 mm.; lengths for all degrees of exposure were similar (7% less than for no exposure). Larval weight (body plus yolk) remained relatively constant (0.099 mg.) until the longest exposure period when it dropped to 0.087 mg. This decrease coincided with similar sharp trends in incubation time and hatching mortality, and suggests a "critical point" near the upper experimental range of exposure, above which eggs stand little chance of normal development or survival. Beach surveys to note possible egg size stratification, although suggesting the deposition of larger eggs at the top levels, proved inconclusive, but point up the possibility that a heavy fishing pressure which reduces mean fish size might detrimentally affect potential stock recruitment via the intertidal exposure effect on the spawn. / Science, Faculty of / Zoology, Department of / Graduate

Histochemical treatments specific for hyaluronic acid, chondroitin sulphate A/C, chondroitin sulphate B, and heparin, which are biological compounds classed as acid mucopolysaccharides, were applied to a series of Pacific great skate (Raja binoculata) embryos in order to characterize histochemically the acid mucopolysaccharides present in the embryos and to study the events leading to the situation of acid mucopolysaccharides localization in the adult. Embryonic stages examined ranged from early cleavage to immediate prehatching. A progression was observed from; 1. intracellular neutral polysaccharides in cleaving stages through, 2. a combination of extracellular neutral polysaccharides and weakly acidic acid mucopolysaccharides (hyaluronic acid) associated with cell processes in neurulating stages to, 3. extracellular strongly acidic sulphated acid mucopolysaccharides (chondroitin sulphates) in later stages, particularly in areas of cartilage development. In neurulating embryos hyaluronic acid appeared in considerable quantity between some adjacent tissue layers in a smooth layer form suggestive of some developmental significance for this compound. Hyaluronic acid also occurred in a similar form in lesser quantity in post neurulae (17-18 mm. embryos) in close association with developing gut and mesonephros. Results of histological tests in immediate prehatching embryos agreed with previously reported biochemical analyses of shark skins and cartilages i.e. chondroitin sulphate B occurred primarily in the skin and chondroitin sulphate A/c were a major component of the cartilage matrix. / Science, Faculty of / Zoology, Department of / Graduate

Call number: LD2668 .T4 1984 S326 / Master of Science

Development in the annual killifish Austrofundulus limnaeus can follow two distinct developmental trajectories. Typical development includes the entrance of embryos into a state of metabolic and developmental arrest termed diapause. Alternately, embryos can escape diapause and develop directly without pause. These two trajectories are characterized by differences in the rate and timing of developmental, morphological, and physiological traits. Insulin and Insulin-like growth factor (IGF) signaling (IIS) is known to regulate entrance into diapause in a variety of invertebrates. In this thesis I explore the possible role of IGFs in the regulation of development and diapause in embryos of A. limnaeus. Here I report stage-specific expression of IGF-I and II proteins and their associated mRNA transcripts. Patterns of IGF-I protein expression are consistent with IGF signaling playing a major role in supporting the escape trajectory. In addition, treatment of embryos with a potent inhibitor of the IGF-I receptor (IGF1R) mimics the diapause developmental pattern even under conditions that should favor direct development. Evaluation of mRNA gene expression patterns in the two developmental trajectories suggests a role for IGF-I signaling through the RAS-MAPK-ERK pathway, which may be promoting the escape phenotype. Additionally, IGF-I activity may be enhanced in escape trajectory embryos though upregulation of IGF binding protein 2 (IGFBP-2) mRNA. These data suggest a major role for IGF signaling in the promotion of the escape trajectory, and thus we predict that specific mechanisms are in place in diapause-bound embryos that block IGF signaling and thus promote entrance into diapause. The data presented here suggest that blocking IGF signaling is critical for induction of diapause, but also suggests that other signaling pathways are likely also at play. Other pathways such at the TGF-beta signaling molecules and SMAD pathway, may also be involved in the direct regulation of the diapause phenotype, as has been shown for other animal models of developmental arrest.