ISSN:
1432-1793
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract The relationship between food ingested and NH + 4 excretion rate was investigated for female Calanus pacificus collected in August, 1982, from the San Juan Archipelago, Washington State, USA. The copepods were preconditioned to 6 densities of the diatom Thalassiosira weissflogii (0 to 104 cells ml−1) for 30 h before the experiment. The experiment was conducted with nutrients added in excess to maintain equal rates of NH + 4 uptake by the diatoms at all densities. Although ingestion rates of C. pacificus varied from 0 to over 20% of body N d−1 at the different food levels, excretion was a constant 6.6 nM NH + 4 copepod−1 h−1 or about 10% of body N d−1. This ingestion-excretion relationship, which is consistent with previous respiration and fecundity studies, suggests that the ecological dominance of C. pacificus only under conditions of high food abundance may be due to a dramatic increase in its growth efficiency as ingestion increases above the level supporting a constant metabolic rate. The maintenance of a constant level of metabolism during relatively short periods of low food abundance may be advantageous if it allows the copepod to exploit more effectively short-term variability in its food resulting from environmental heterogeneity or vertical migration.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00393012
