Effects of T-2 toxin on digestive enzyme activity, intestinal histopathology and growth in shrimp Litopenaeus vannamei

Abstract

T-2 toxin (T-2), a naturally occurring mycotoxin that often accumulates in aquatic animals via contaminated feed, is toxic to animals, including humans. In this study, six groups of shrimp (n = 30 shrimps/group) were given T-2 in feed at concentrations of 0-12.2 mg/kg for 20 days. T-2 accumulation, intestinal histopathology, digestive enzyme activities and subsequent effects on shrimp are reported. Compared to the control, T-2 significantly reduced weight gain, specific growth rate, and survival. The histopathology of shrimp intestine showed concentration-dependent degenerative and necrotic changes in response to dietary T-2. Progressive damage to the microstructures of shrimp intestine occurred with increasing dietary T-2 concentrations, with initial inflammation of the mucosal tissue at T-2 concentrations of 0.5 and 1.2 mg/kg, progressing to disappearance of intestinal villi and degeneration and necrosis of the submucosa at 12.2 mg/kg. Intestinal amylase and protease activities increased at low T-2 concentrations but showed significant inhibition at high concentrations; however, the opposite trend occurred for lipase activity. Collectively, these results indicate that digestive enzyme activities and mucosal structures are markedly affected by exposure to T-2, and these may have contributed to the lower survival rate of shrimp.

Figure 1

Reductions in growth parameters and survival as a function of dietary concentrations of T-2 toxin. Different superscripts indicate significant differences. Weight gain is shown as WG, specific growth rate is shown as SGR, and survival rate is shown as SR.

Figure 2

Histopathology of shrimp intestine exposed T-2 (×400). Description of letter abbreviations: A- Striated border, B- Mucosa, C- Submucosa, and D- Muscular layers. Figures a to f are the shrimp given 0 (control), 0.5, 1.2, 2.4, 4.8, 12.2 T-2 mg/kg respectively.

Figure 3

The effect of T-2 on digestive enzyme activities (Mean + SD) in shrimp intestine. Bars with different superscript letters for each enzyme are significantly different (P < 0.05) compared with the control (0).

Figure 4

Effect of T-2 exposure concentration on the ratio of amylase enzyme activity (treatment group/control group) in shrimp intestine. NOAEL: No Observable Adverse Effect Level; EC₅₀: T-2 concentration for 50% of amylase enzyme activity.

Figure 5

Effect of T-2 exposure concentration on the ratio of intestinal protease enzyme activity (treatment group/control group) in shrimp intestine. NOAEL: No Observable Adverse Effect Level; EC₅₀: T-2 concentration for 50% of protease enzyme activity.

Figure 6

Effect of T-2 exposure concentration on the ratio of intestinal lipase enzyme activity (treatment group/control group) in shrimp intestine. NOAEL: No Observable Adverse Effect Level; MEC: T-2 concentration of maximal lipase enzyme activity.