A study of biochemical composition in captive Atlantic halibut (Hippoglossus hippoglossus) eggs and larvae

Zhu, Peihong (1999) A study of biochemical composition in captive Atlantic halibut (Hippoglossus hippoglossus) eggs and larvae. Masters thesis, Memorial University of Newfoundland.

[English] PDF (Migrated (PDF/A Conversion) from original format: (application/pdf)) - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (14MB) [English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. (Original Version)

Abstract

In this study, lipid classes, fatty acids, free amino acids (FAA) and protein content in captive Atlantic halibut (Hippoglossus hippoglossus) eggs were measured to investigate the relationship between biochemical composition of the eggs and egg quality, the effect of the physiological condition of broodstock females on egg biochemical composition, and changes in the biochemical composition of eggs and larvae in both the embryonic and early larval stages. -- High neutral lipid (NL) level and low (n-6) and (n-3) polyunsaturated fatty acid (PUFA) levels seem to be associated with low egg quality. For eggs with a fertilization success ≥ 75%, there were significantly lower amounts of total NL and sterol (ST) per egg (P<0.01, P<0.05, respectively) compared to eggs with a fertilization success < 75%. For eggs that produce larvae with survival time ≥ 15.9 days, the amount of triacylglycerol (TAG) was significantly lower than in eggs that produced larvae with survival times < 15.9 days (P<0.01). For eggs with a fertilization success ≥ 75%, the proportion of (n-6) PUFA in TAG (P<0.01), the proportion of 20:5 (n-3) in phosphatidylethanolamine (PE) (P<0.05), and 18:2 (n-6) (P<0.05) in the total lipid per egg, were significantly higher than for eggs with fertilization success < 75%. -- The average dry weight of eggs followed a pattern similar to that of the average food intake of the broodstock female, while the average egg lipid content did not change. The spawning rhythm of the females also affected egg composition. The ash free dry weight and total protein of the eggs decreased as the spawning season proceeded (P<0.05). In TAG, the levels of 18:0 and 20:4 (n-6) per egg, and in PE, the level of (n-6) PUFA per egg decreased significantly over the spawning season (P>0.05). The maturity of the spawners affected egg quality and egg lipid composition as well. Repeat spawners produced eggs with significantly higher fertilization success than first-time spawners (P<0.05). The total neutral lipid (TNL) and ST were significantly lower for eggs from repeat spawners than for eggs from first-time spawners (P<0.01, P<0.05, respectively). -- Total FAA decreased continuously (p<0.01) over the embryonic and larval stages investigated. TAG decreased significantly for the larval stages (P<0.05). When hatching occurred, there was a significant increase in all lipid classes except ST. It is suggested that FAA may be the source of carbon skeletons for lipid synthesis at hatching. -- Thus, this study has shown that lipid and fatty acid composition in eggs from captive Atlantic halibut is associated with egg quality; however, FAA are the biochemical components that are most utilized during embryonic and early larval stages. At the end of embryonic stage and early larval stage, these amino acids appear to be directed towards lipid synthesis and then towards protein synthesis.

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