Comments

Originally published in Biological Bulletin and used with permission.

Abstract

Transport rates of amino acids were determined for larvae of different ages of the echiuran worm Urechis caupo, the gastropod Haliotis rufescens, the bivalve Crassostrea gigas, and the sea urchin Strongylocentrotus purpuratus. All larval forms showed an increase in the transport rate of amino acids during development. Trochophores of U. caupo increased their rate of net flux for each of 5 amino acids (100 nM each) by a factor of 1.6 and 2.2 during 1-3 days and 4-8 days, respectively, for two independent cultures. In H. rufescens, the maximum transport capacity (Jmax) for alanine increased 3-fold during the 24 h required for the trochophore to develop into a veliger. In C. gigas veligers, there was a 9-fold increase in the maximum transport capacity for alanine during larval development from an 80 μm to a 300 μm larva. In sea urchins, the prism-stage larvae (2-day-old) had an alanine transport system with a Kt of 1.9 μM and a Jmax of 8.1 pmol larvae -1h-1. The kinetics of alanine transport in the pluteus-stage (4-day-old) were best described by two systems (System I: Kt = 1.0 μM with a Jmax of 5.6 pmol larva -1h-1; System II: Kt = 132.0 μM with a Jmax of 8.4 pmol larva -1h-1). In larvae of C. gigas, the relationships between the rate of alanine transport and body size was described by the equation, log Jmax (pg larva-1h-1) = 1.6894(X) + (-0.5937), where X is the shell length in μm. It is illustrated that the allometric increased in respiration rates, during the growth of bivalve larvae, is matched by an ontogenic increase in amino acid transport capacity.

Disciplines

Biology, general | Physiology