ABSTRACT: The polychaetes Nereis diversicolor and N. virens were fed various amounts of shrimp meat in laboratory experiments and linear relationships between specific growth rate and specific respiration rates were found. From this relation the energy cost of growth ('specific dynamic action', SDA) was found to be 20 to 26% of the growth. The starvation respiration rate (maintenance) (R_m, ul O₂ h^-1 ind.^-1) as a function of body mass (W, g dry wt) was: R_m = 1306W^1.2 and R_m = 704W^1.0 for N. diversicolor and N. virens, respectively. For worms fed shrimp meat the maximum specific growth rate was 7% d^-1 in N. diversicolor and 5.9% d^-1 in N. virens. In filter-feeding N. diversicolor fed algal cells (6.2 um diameter Rhodomonas sp.) there was a strong correlation between ingestion rate and growth rate, the maximum specific growth rate being 3% d^-1. No functional response was seen even at the highest algal concentration of 2 x 10⁴ cells ml^-1. It is possible that filter-feeding in N. diversicolor is a relatively recent adaptation which has resulted in a broader fundamental niche compared to that of the closely related N. virens. This filter-feeding adaptation may possibly explain the coexistence of the 2 polychaetes in certain brackish water areas.

KEY WORDS: Feeding . Growth . Respiration . Costs of growth . Specific dynamic action (SDA) . Net growth efficiency . Filter-feeding

Published in MEPS Vol. 125 (1995) on September 14
ISSN: 0171-8630. Copyright © Inter-Research, Oldendorf/Luhe, 1995