S. Petersen et al., ON THE NUTRITIVE SIGNIFICANCE OF DISSOLVED FREE AMINO-ACID-UPTAKE FORTHE COSMOPOLITAN OLIGOCHAETE NAIS-ELINGUIS MULLER (NAIDIDAE), Estuarine, coastal and shelf science, 46(1), 1998, pp. 85-91
Uptake of dissolved free amino acids (DFAA) by Nais elinguis Muller fr
om a brackish water lagoon has been confirmed by autoradiographic stud
ies, liquid scintillation counting of animals incubated with labelled
DFAA, and by HPLC analysis of the incubation water. Net uptake was sho
wn to occur at ambient DFAA concentrations. The results indicate that
most of the absorbed DFAA were respired, and only a minor portion was
incorporated into proteins. Parallel determination of respiration and
DFAA uptake in a flow-through system allowed a calculation of the cont
ribution of uptake to the maintainance metabolism of N. elinguis. The
average weight-specific uptake rate of mixed DFAA was 1.4 mu mol g(-1)
h(-1) at a salinity of 6 and 4.1 mu mol g(-1) h(-1) at a salinity of
12 (temperature 20 degrees C). Assuming that 10 mu mol of mixed amino
acids (average mol wt. 100) require 44.64 mu mol O-2 for complete oxid
ation, the nutritional profit of DFAA absorption at a salinity of 6 ac
counted for 7% of the total oxidative needs and for 24% at a salinity
of 12. The results demonstrate that DFAA uptake can provide an importa
nt nutritional input. (C) 1998 Academic Press Limited.