9334

• UCREFRP Catalog Number: 9334
• Author: Stickney, R. R.
• Title: Editor
• USFW Year: Series
• USFW - Doc Type: 1993
• Copyright Material: YES

Reviews in Fisheries Science, 1(3~: 239-259 (199,3)
Metabolic Aspects of Free Amino Acids
in Developing Marine Fish Eggs
and Larvae
Ivar R~nnestad
Institute of Nutrition, Directorate of Fisheries, P.O. Box 1900 Nordnes, N-5024 Bergen,
Norway
Hans JBrgen Fyhn
Zoological Institute, University of Bergen, Allegt 41, N-5007 Bergen, Norway
ABSTRACT: Investigations during the last decade have shown that free amino acids (FAA)
abound in marine pelagic fish eggs. The concentration in the egg (about 150 mill) is well
above what is typically found in adult teleostean tissues. FAA in fish eggs were initially studied
in order to evaluate their role as osmolytes. More recently, however, FAA have been
implicated as a fuel in the energy metabolism of developing marine fish eggs and larvae.
Further aggregation of data verifies that pelagic eggs of marine teleosts generally have a high
content of FAA. The large pool of FAA is almost exclusively contained within the yolk-sac
compartment. The relative composition of the FAA pool shows little interspecific variation.
The FAA pool is depleted during development and reaches low levels at first feeding. The
observed decline in the FAA content during development is not due to a loss of FAA to the
ambient water, but rather results from endogenous metabolic turnover. FAA seem to be
utilized to varying extents for body protein synthesis, but are more often used as substrates
in energy metabolism.
KEY WORDS: Free amino acids, protein, metabolism, energy, development, marine fish
eggs and larvae, endogenous nutrients.
1. INTRODUCTION
A. BACKGROUND
Abundant free amino acids (FAA)* in marine invertebrate phyla have long been
known to represent an osmotic adaptation in seawater (Gilles, 1979; Fugelli, 1980;
Yancey et al., 1982). The large intracellular FAA pool may comprise 30 to 50% of
the cytoplasmic osmolality (Fyhn, 1976; Pierce, 1981; Forward and Fyhn, 1983)•
Variance in the FAA pool composition exists among taxonomic groups, but generally
some of the nonessential amino acids, such as glycine, alanine, proline, serine,
`Freely dissolved amino acids as opposed to amino acids polymerized in peptides and proteins.
1064-3262 f93/$.50
©1993 by CRC Press 239