JOURNAL OF PLANKTON RESEARCH | VOLUME 6 | NUMBER 3 | PAGES 505-513 | 1984
© Oxford University Press
research-article |
Ammonium release by juveniles and adult females of the subtropical marine copepod Eucalanus pileatus1
2Skidaway Institute of Oceanography P.O. Box 13687, Savannah, GA 31416 3National Oceanic and Atmospheric Administration, Great Lakes Environmental Research Laboratory 2300 Washtenaw Avenue, Ann Arbor, MI 48104, USA
Received on September 1, 1983; accepted on February 1, 1984
Release rates of ammonium by nauplii, copepodid stages (CII and CIV) and adult females of the marine copepod Eucalanus pileatus at 0.1 and 3.0 mm3 1–1 of the diatom Thalassiosira weissflogii were determined at 20°C. When food was abundant, animals of all stages released ammonium at similar rates per unit ash-free dry weight [24–35 nmol NH4(mg AFDW)–1 h–1 on average]. At low food levels, CIVs and adult females released ammonium significantly more slowly than did the naupliior CIIs [28 and 24 versus 51 and 50 nmoles(mg AFDW)–1h–1]. Because they weighed less (50%), low-food nauplii and CIIs had higher calculated weight-specific excretion rates, than high-food ones of the same stage but release rates per copepod were similar in the two food regimens. In contrast to the early life stages, the CIVs and adult females released less ammonium per copepod in the low-food than in the high-food environment.