Date of Award
Doctor of Philosophy (PhD)
James H. Power
A sensitive methodology for the determination of RNA and DNA concentrations was developed which allowed for the quantification of nanogram amounts of both DNA and RNA. The method uses a combination of thiazole orange, a non-specific nucleic acid stain, and the RNA degrading enzyme RNase. Thiazole orange had high fluorescence yield. The fluorescence was additive for combinations of RNA and DNA. The addition of proteinase-K increased the fluorescence of the tissue sample by 100%. Recovery of nucleic acid standards added to tissue extracts yielded $\sim$100% recovery. The method is compatible with assays for protein concentration and electron transport system (ETS) enzyme activity. Menhaden (Brevoortia patronus) larvae and meteorological data were collected for 2 week intervals during the winters months of 1993-1994 and 1994-1995 in an examination of the role of atmospheric frontal passage on larval condition. Three biochemical assays were used to quantify larval condition, RNA:DNA, protein concentration and ETS activity. Each day of collection was categorized in terms of the prevailing atmospheric conditions. The larvae were in good condition and there was no consistent trend in the condition of the larvae through the two spawning season. There was no indication that poor condition larvae were being lost from the population. Larval condition was not strongly affected by water temperature or any meteorological variable. All condition indices were highest during periods of southerly winds associated with the progression of atmospheric cold fronts. The variation in condition indices among the months of collection and between the years of collection can be explained by the frequency of the atmospheric cold fronts. The increase in larval condition in association with the cold fronts is likely a result of the increased encounter rate with prey items due to an increase in wind-generated turbulence. A new morphometric analysis technique based upon the thin-plate spline was examined as a low-cost alternative to the biochemical measures of condition. This method of shape analysis was not successful in identifying the known condition of the larvae. The short-term influence of the atmospheric cold fronts was of insufficient intensity to generate morphological change in the larvae.
Burger, Michael John, "Temporal Variation in Larval Fish Condition Indices." (1998). LSU Historical Dissertations and Theses. 6619.