Tolerance and bio-accumulation of aflatoxin B1 in invertebrate Litopenaeus vannamei and vertebrate Oreochromis niloticus

Abstract

Aflatoxin B1 (AFB1) is a mycotoxin that is commonly detected in aquatic feed in tropical and subtropical regions. The toxic effects in shrimp and fish tissues following exposure to chronic AFB1 exposure has been studied but there is no information on tolerance between different species. This study was designed to compare the tolerance of AFB1 between invertebrate Litopenaeus vannamei and vertebrate Oreochromis niloticus. The emphasis was on growth profile, biotransformation, histopathology and AFB1 accumulation following exposure to increasing doses of AFB1. 182 shrimps and 146 tilapia were used and divided into control and AFB1 exposure groups. Shrimp were exposed to 1.5-fold increasing doses of 1.2, 1.8, 2.7, 4, 6 mg/kg AFB1 and tilapia to 3.2, 4.8, 7.2, 10.8, 16.2 mg/kg of AFB1 for 20 d with a 4-day exposure to each AFB1 with the shrimp/fish sacrificed on the last day of exposed dose(s). At each time point the controls were also sacrificed. A significant decrease in survival rate and weight gain (WG) was observed in shrimp. Higher AFB1 doses caused a decline in tilapia WG. Dose responsive AFB1 accumulation was evident in muscle and shrimp hepatopancreas /tilapia liver. The concentration of AFB1 was significantly higher in shrimp hepatopancreas (22.76–72.89 ng/g) than in tilapia liver (6.68–19.45 ng/g) in spite of exposure to a higher dose regime. The muscle AFB1 concentration in both species ranged from 0 to 20 ng/g. The shrimp hepatopancreas cytochrome b5 (Cyt b5) concentration increased initially but declined after >4 mg/kg AFB1 exposure. The tilapia liver Cyt b5 content declined after >10.8 mg/kg AFB1. In the shrimp hepatopancreas, a marked induction of enzymes, aniline hydroxylase (AH), NADPH-cytochrome P450 reductase (NCCR), 7-ethoxyresorufin O-deethylase (EROD), glutathione-S-transferase (GST), sulfotransferase (SULT) and uridinediphosphate glucuronyltransferase (UGT) were observed. Only some of these enzymes, namely, EROD, GST, UGT and SULT but not AH or NCCR were induced in tilapia liver. Hepatopancreas/liver damage in shrimp/fish was marked at higher AFB1 doses. Marked changes in the shrimp hepatopancreatic cell structure was observed in shrimp at concentrations >6 mg/kg AFB1. This study showed that shrimp are more susceptible to AFB1 than tilapia and further studies are required to determine the role of AH and NCCR enzymes in species differences to AFB1 toxicity.