The ontogeny of greater amberjack digestive and antioxidant defense systems under different rearing conditions: a histological and enzymatic approach
Date
2020Abstract
An overall synchronization of morphological and physiological ontogenetic events of
the digestive and antioxidant defence systems occurred in greater amberjack (Seriola
dumerili) larvae reared under intensive (INT) or semi-intensive (MES) conditions for
30 days. The first differentiations of the digestive channel took place at 3–4 days
post-hatch (dph) (3.6–3.7 mm). Differentiation of the endocrine and exocrine pancreas begun at 4–5 dph (4.0–4.1 mm), coinciding with a decrease in carbohydrase
activity from egg to the onset of exogenous feeding and the maintenance of bile
salt-activated lipase and total alkaline proteases. The first gastric glands and pepsin
activity were evident at 17–20 dph (5.5–6.2 mm) in both fish groups. The appearance
of pyloric caeca had a 5-day delay in the INT compared to the MES larvae (28 versus
23 dph). Antioxidant enzyme activities decreased progressively from 7 to 30 dph in
both rearing conditions. However, GPx, SOD at 7 and 18 dph, and GST activities were
higher in the INT larvae. Although both larval groups did not globally differ in somatic
growth and maturation of digestive function, it seems that the antioxidant defence
system of MES larvae had to face less oxidative assaults, which may be attributed to
lower stressful and more stable culture conditions.