SOURCES OF ENERGY FOR INCREASED METABOLIC DEMAND DURING METAMORPHOSISOF THE ABALONE HALIOTIS-RUFESCENS (MOLLUSCA)

Pelagic, lecithotrophic (nonfeeding) larvae of the red abalone (Haliot is rufescens) settle and subsequently metamorphose into benthic juveni les capable of Feeding on particulate food. Thus, metamorphosis must b e fueled by either endogenous reserves or a nonparticulate food source such as dissolved organic material (DOM) in seawater, The metabolic r ates (measured as oxygen consumption) of abalone larvae were found to increase by an average of 3- to 5-fold from the larva to early juvenil e stage, The total cost of development from embryo to juvenile measure d for three cultures ranged from 41.6 mJ to 55.0 mJ. Meeting this cost would require 1.3 to 1.7 mu g of biomass (ash-free dry mass), which i s similar to the initial biomass of the spawned oocyte at 1.36 +/- 0.0 4 mu g (mean of four cultures). However, there was no net loss of biom ass during development from the oocyte to the juvenile, The uptake of alanine alanine and glucose from seawater by larvae and juveniles coul d provide one-third of the organic material required po supply metabol ism, even if the transporters were only operating at 20% of their maxi mum capacity throughout development, For larvae undergoing metamorphos is (between 6- and 9-days-old) the proportion of total metabolic deman d supplied using aerobically catabolized biomass was only 39%. The hig her metabolic rates of metamorphosis are met only in part by consuming stored endogenous reserves. Concomitant with an increase in mass-spec ific metabolic rate during metamorphosis, the maximal capacity (J(max) ) for the transport of dissolved alanine from seawater increased 3-fol d, from 61.2 +/- 1.9 (SE) to 182.0 +/- 49 pmol alanine individual(-1) h(-1), The majority (range: 61% to 100%) Of the energy requirements of larval and early juvenile development of H. rufescens could be suppli ed by input of DOM from the environment, Measurements of transport rat es of amino acids and sugars by these animals, and calculations of the energy input from these substrates, indicate that the cumulative tran sport of DOM from seawater during development to the early juvenile st age could supply an amount of energy equivalent to the initial materna l endowment of energy reserves to the oocyte of this lecithotrophic sp ecies.