Comparative Biochemistry and Physiology Part A 125 (2000) 437 – 443 Metabolic responses of the white shrimp, Penaeus annamei, to ambient ammonia Ilie S. Racotta *, Roberto Herna ´ndez-Herrera Diisio ´n Biologı ´a Marina, Centro de Inestigaciones Biolo ´gicas del Noroeste, Apdo. Postal 128, La Paz B.C.S. 23000, Mexico Received 4 February 1999; received in revised form 24 January 2000; accepted 31 January 2000 Abstract Juvenile shrimp were individually exposed during 24 h to 0.007 (control), 0.36, 1.07, and 2.14 mmol/l total ammonia-N at 28°C and 39 ppt salinity. After 22 h of ammonia-N exposure, oxygen consumption was measured for 2 h, and then hemolymph, hepatopancreas, and muscle tissues were sampled. Oxygen consumption, and levels of lactate and glycogen in the hepatopancreas increased significantly at the highest ammonia-N concentration. Concentration of oxyhemocyanin, acylglycerol, and cholesterol in hemolymph, and lactate in muscle decreased significantly in the group exposed to the highest ammonia levels. The changes observed in hemolymph and tissue metabolic fuels suggest a reduced use of carbohydrate through anaerobic metabolism and an increase in the use of lipids to satisfy the metabolic demand. © 2000 Elsevier Science Inc. All rights reserved. Keywords: Ambient ammonia; Oxygen consumption; Lactate; Lipid; Metabolism; Protein; White shrimp; Penaeus annamei www.elsevier.com/locate/cbpa 1. Introduction An important environmental concern associ- ated with intensive shrimp culture is the produc- tion of high levels of ammonia, the principal form of excreted nitrogen in crustaceans. Total ammo- nia can reach 6.5 mg/l (0.46 mmol/l) after several weeks of shrimp culture (Chen and Lin, 1992). Intensive shrimp farming, with shrimp stocked at high density in ponds and a large number of ponds operating in a small area with poorly de- signed water uptake and discharge, can cause self pollution (Csavas, 1994; Currie, 1994). As a re- sult, sustained high levels of ammonia would af- fect the shrimp and can partially explain why intensive shrimp farming is often not sustainable. Some alternatives have been proposed to diminish the ammonia load, i.e. reduction of protein levels in the diet (Hopkins et al., 1995; Velasco et al., 1996). However, the effects of ammonia-N di- rectly on shrimp are not yet clear. In penaeid species, ammonia toxicity has been studied by Chen and coworkers (Chen and Cheng, 1993; Chen et al., 1994). However, their work is limited to Asian species and evaluations are necessary for cultured American species such as Penaeus annamei. Ammonia toxicity has been shown to affect survival (Chen and Lei, 1990), growth and molting (Chen and Kou, 1992), am- monia-N accumulation and excretion (Chen and Lin, 1992; Chen and Cheng, 1993; Chen et al., 1994), and other physiological aspects (Chen and Lin, 1992; Chen et al., 1993, 1994). In Asian species, ammonia or its oxidation product, nitrite, caused an increase in oxygen consumption as reported for P. chinensis (Chen and Lin, 1992, * Corresponding author. Tel.:/fax: +52-112-54715. E-mail addresses: iracotta@cibnor.mx (I.S. Racotta), rherrera@cibnor.mx (R. Herna ´ndez-Herrera) 1095-6433/00/$ - see front matter © 2000 Elsevier Science Inc. All rights reserved. PII:S1095-6433(00)00171-9