Oogenesis in Mytilus californianus Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/vd66w287w

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  • A two-year field study was made of a population of the California Sea Mussel, Mytilus californianus, located on a protected tidal bench at Yaquina Head on the Central Oregon Coast. This animal was chosen because it is attached to the rocks, filters particulate matter from the water, produces large amounts of eggs, and is a prominent member of the intertidal community. An equation was developed on both an empirical and a theoretical has is for determining mussel tissue temperature from continuously, recorded physical data in order to determine the annual temperature trends and the daily rate of heating. Heating during exposure is an important contribution to mussel temperature during the spring and possibly during the fall. Particulate organic material 100 to 200 m in diameter was measured throughout the year and was found to range from 1 to 3 mg dry weight per liter of sea water. During the spring, increases in particulate oxidizable material are associated with diatom blooms. The rest of the year, detritus associated with the mixing action of waves contributes a significant portion to the suspended particulates. A gonad index was developed which separated the germinal tissue from the storage tissue in the gonad. The denominator of this index equation was the weight of the somatic tissue rather than the total weight of the animal. The largest amount of reproductive tissue observed was 800 mg per gram dry weight of somatic tissue, but the population generally maintained a germinal gonad index of about 60% of its potential maximum. The storage stage was found to be greatly reduced in this population unlike that found in M. edulis. The seasonal reproductive progress was studied by quantitatively following three categories of oocyte stages. The number of oogonial clusters was used as an index of mitotic activity. Few clusters of oogonia appeared when numerous mature oocytes were present. The number of previtellogenic oocytes was taken as an index of early meiotic activity. Previtellogenic processes were initiated during the spring when the tissue temperature was rising. Mature oocyte numbers increased as vitellogenesis occurred, and the rate of increase of mature oocytes was best correlated with particulate organic concentration in the water. Partial spawning and resorption of lysed eggs were the predominant fate of mature eggs. The dynamic aspect of oogenesis was followed using a flow model for the categories of occyte stages. From this model rates of change of each cell type were estimated. Only 40% of the total oocytes produced throughout the year was lost by spawning. Gonadal tissue was chemically divided into biochemical fractions to determine the chemical characteristics of each reproductive stage and the rates of accumulation of chemical components between bimonthly samples. The rates of accumulation of protein and lipid increased from 1.7 to 3.6 mg per day per gram animal and 0.6 to 1.8 mg per day per gram animal during previtellogenesis and vitellogenesis respectively. RNA increased at the rate of 0. 6 mg per day per gram animal, while the amount of glycogen decreased. Isochrysis galba, a flagellate, labeled with carbon-14 was fed to mussels under different exposure and thermal regimes to determine the rate of incorporation and the percentage of food allocated to the gonad. For mature gonads undergoing partial spawning, about 10% of the food was found in the gonadal tissue within 3 days. The translocation and synthetic pathways associated with protein and RNA appear to be the most active. The amount of protein per egg determined directly or indirectly was found to decrease as the reproductive year progressed. A hypothetical scheme for the environmental and physiological control of oogenesis M. californianus is presented and evaluated in terms of the data. As a result o the observed timing of events and the variation in the population, elucidation of the relationship between reproductive phenomena and the environment by conventional techniques would require analysis of 50 to 70 specimens every 2 weeks for a period of at least 2 years.
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  • File scanned at 300 ppi (Monochrome, 256 Grayscale) using Capture Perfect 3.0.82 on a Canon DR-9080C in PDF format. CVista PdfCompressor 4.0 was used for pdf compression and textual OCR.
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