Dietary vitamin C supplementation potentiates the formation of giant cells in pacu Piaractus mesopotamicus Holmberg, 1887 (Osteichthyes: Characidae)

Abstract

Juvenile specimens of pacu Piaractus mesopotamicus (n=120), with average initial body weight of 32.06 ± 3.56 g and average initial length of 11.08 ± 0.41 cm, were reared under laboratory conditions, and the interference of vitamin C (ascorbic acid) on the giant cells formation was evaluated. Fish received ration with different ascorbic acid levels (0, 100, 200, 500 mg of vitamin C/kg ration) for 40 days. After that time, sterilized round glass coverslips (11 mm diameter) were implanted in the subcutaneous tissue in order to study the formation of giant cells. The glass coverslips were taken out at different times (3, 7, and 14 days after implants were done). The cell count on glass coverslips could be performed until 14 days after they were implanted. The coverslips taken three days after implants were done revealed that the vitamin C supplementation had no influence on the analyzed parameters in this phase. The number of macrophages present in glass coverslips increased with time (p < 0.01). Seven days after the implants were made, fish treated with 100, 200 or 500 mg vitamin C/kg ration presented significantly higher number of giant cells (independent of number of nuclei and cell morphology) than those fish treated without supplementation (0 mg vitamin C/kg ration). Fish treated with 100 mg vitamin C/kg ration showed a significant increase in the number of giant cells from the 3th to the 7th day, while fish treated with 200 or 500 mg vitamin C/kg ration presented a higher number of these cells after 7 days, being significantly reduced 14 days after the implants were done. The number of Langhans cell type raised progressive and significantly with time (p < 0.01).