C.M. Ryan, G.J. Parsons, P. Dabinett
Abstract:
The effect of diets of algae harvested from log and near stationary phase cultures on growth of scallop larvae and spat was investigated. Larvae were fed 20 cells/micro L of a standard diet consisting of a mix of equal numbers of six algal species (Isochrysis galbana, Isochrysis (clone T.ISO), Pavlova lutheri Thalassiosira pseudonana (clone 3H), Chaetoceros gracilis, Chaetoceros ceratosporum) in four growth trials. Juvenile scallops (spat) were stained using calcein (0.15 g/L of seawater), a non-toxic stain which is bound during calcification of the shell and which fluoresces bright yellow-green under epifluorescence microscopy. The resulting fluorescent band was used as a benchmark from which to measure new growth during feeding trials. Calcein stained spat were fed 40 cells/micro L of a standard diet in four growth trials. Samples of algae were taken during two of the spat trials and analysed for lipid class composition. Total lipids were extracted with a mixture of chloroform and methanol. The Chromarod-Iatroscan TLC/FID system was used to identify and quantify lipid classes. The relationship of spat growth to lipid class composition of the diet was explored using the Spearman rank correlation coefficient.
Results indicate that in 3 out of 4 experiments conducted, larvae fed log phase algae were significantly larger than those fed stationary phase algae (t-test, P<0.05). Similar results were obtained with spat from four feeding trials (t-test, P<0.05). In two of these initial trials, significant (p<0.01, 2-tailed) positive correlations were obtained for spat growth and methyl ketones and sterols, and significant negative correlations for spat growth and alcohols, ethyl ketones, free fatty acids, hydrocarbons, phospholipids, total lipids and sterol and wax esters. Acetone-mobile polar lipids, diacyl glycerols, and triacyl glycerols were not significantly correlated to growth in these trials.
(Marine Institute, Memorial University, P.O. Box 4920, St. John's, NF A1C 5R3, Canada)
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