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.