EFFECT OF UNIONIZED AMMONIA VISCOSITY AND PROTOZOAN CONTAMINATION ON THE ENZYME ACTIVITY OF THE ROTIFER BRACHIONUS PLICATILIS

A.B. de Araujo, T.W. Snell, A. Hagiwara-2000

Aquaculture Research, 31 (4): 359-365

Abstract:

Substrates that are cleaved to yield fluorescent products can be used to quickly quantify enzyme activity in vivo with image analysis or in vitro with fluorometry. This study was carried out to determine whether enzyme activity in rotifers is useful for assessing the physiological condition of rotifers. Neonates of Brachionus plicatilis Müller hatched from cysts were exposed to a concentration series of unionised ammonia ranging from 0 to 9.8 p.p.m., increasing seawater viscosity relative to 1.17 to control sea water by the addition of methyl cellulose and the addition of the protozoan Euplotes sp. to a density of 40/ml. Rotifer glucosidase and esterase activities decreased with increasing unionised ammonia and viscosity respectively. Activities of glucosidase and phospholipase decreased with increasing protozoan contamination. There was a significant relationship between enzyme activities and rotifer population growth. In vivo activities of certain rotifer enzymes can therefore serve as biomarkers for the rapid assessment of environmental stressors in rotifer mass cultures.

(Graduate School of Marine Science and Engineering, Nagasaki University, Bunkyo 1-14, Nagasaki 852-8131, Japan)

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