Changes of digestive enzymes in totoaba (Totoaba macdonaldi Gilbert, 1890) during early ontogeny

Abstract

Totoaba macdonaldi is an endemic specie which has been overexploited causing its population to decrease and to be cataloged as endangered. Understanding the larval period is the most critical stage in the development of marine fish farming. Our study aims to determine the changes of digestive enzyme activities during the early ontogeny of totoaba, using biochemical and electrophoretic techniques. The results show that the acid protease had maximum activity between days 28 and 32 DPH, when the Artemia was replaced by formulated food. Alkaline protease activity was detected at 2 DPH with maximal activity between 20 and 32 DPH; trypsin activity became active from 2 DPH; chymotrypsin activity increased at 6 DPH; leucine aminopeptidase activity was detected at 3 DPH, showing its maximal level at 22 DPH; carboxypeptidase A activity increased at 3 DPH; and lipase and amylase activities were detected at 2 DPH. Acid zymogram showed only one isoform (0.72 rf) from 2 DPH and increased in intensity from 8 DPH. For alkaline proteases, four isoforms were detected from yolk absorption (1 DPH), increasing to six isoforms (77.8, 47.3, 43.5, 21.0, 19.2 and 17.5 kDa) from 8 DPH onwards. Our results show that larvae of T. macdonaldi present characteristics typical of carnivore marine fish, showing the presence of alkaline digestive enzymes prematurely and the presence of offset pepsin. T. macdonaldi can be consider to be a youth beginning at 28 DPH, this being the most appropriate day to perform replacement by artificial food.