RESUMO
A 2-week research was carried out to assess water salinity (WS) effects including 0, 15, 35, and 50 on osmoregulatory mechanisms and stress indices in Asian sea bass (34.4 g) juveniles. Except for fish reared at 50, in the other treatments, it gradually decreased to the prescribed WS during a 10-day period (- 5 a day). After a 10-day acclimation period, fish were reared at the prescribed WS for 2 weeks. Fish reared at 15 and 35 had higher chloride cell (CC) counts in the interlamellar region. The number of CC in the interlamellar region elevated with increment of WS up to 35, but they were pronouncedly reduced in 50 group. The diameter of CC in the interlamellar region was not affected by WS. The smallest nucleus diameter of CC in the interlamellar region was observed in fish reared at 15 (P < 0.05). The largest and the smallest amounts of serum aspartate aminotransferase were observed in fish reared at freshwater and 15, respectively. Fish reared at 35 had the highest serum sodium and potassium contents. Serum chloride content and total osmolality increased with increment of WS (P < 0.05). Serum cortisol and glucose contents gradually increased with elevation of WS up to 35; then, their contents remarkably decreased. The relative expression of insulin like growth factor-1 in the liver of fish reared at 35 was strikingly higher than that in the other groups. The relative expression of HSP70 gene in fresh water group was pronouncedly elevated compared to other treatments. The relative expression of interleukin-1ß in 15 and 35 groups was higher than that in the other groups; however, the relative expression of lysozyme gene in the liver of fish reared at fresh water was pronouncedly lower than that in the other treatments. The results of this study suggested rearing L. calcarifer at 15 closer to the isosmotic point and better provide its welfare.
Assuntos
Cloretos/sangue , Brânquias , Perciformes , Salinidade , Animais , Expressão Gênica , Perciformes/fisiologiaRESUMO
The present research was conducted to provide insight into digestive larval capacity in Acanthopagrus latus larvae from hatching up to 30 days after hatching (DAH). Newly hatched larvae were stocked into six 300-L cylindrical polyethylene tanks at a density of larvae 50 larvae/L and reared by means of the green water system using Nannochloropsis oculata (0.5 × 106/mL). After mouth opening, larvae were fed with rotifers (5-16 individual/mL) from 2 to 20 DAH; then, Artemia nauplii (0.5-3.0 individuals/mL) were offered to larvae from 18 to 30 DAH, meanwhile a commercial microdiet was offered to larvae from 25 to 30 DAH. Larval performance in terms of growth and survival, and the assessment of the activity of selected digestive enzymes ontogeny of digestive enzymes activities was evaluated in larvae sampled at 0 (hatching), 7, 15, 22 and 30 DAH. Larvae showed an exponential growth characterized by two different growth stanzas, a first one characterized by slow growth rates comprised between hatching to 15 DAH (4.7 ± 0.2 mm), followed by a period of faster growth rates between 16 and 30 DAH (7.5 ± 0.6 mm). The activities of the brush border (alkaline phosphatase, ALP) and cytosolic (leucine-alanine peptidase, LAP) enzymes, as well as those of the pancreatic ones like total alkaline proteases, bile salt-activated lipase and α-amylase were detected from the mouth opening stage. Total activities of pancreatic and gastric enzymes increased with larval growth showing an enhancement of digestive capacities with larval age and size. The intestinal maturation in A. latus as assessed by the ratio of AP to LAP did not occur as expected by end of the first month of life suggesting the complete establishment of digestive luminal processes may take place at older ages. This study related to the growth patterns and ontogenic changes in activity of pancreatic, gastric and intestinal enzymes in A. latus and their nutritional regulation may be considered as the first step for improving the larviculture, as well as assessing and refining the nutritional requirements during the larval and early juvenile stages of this sparid species.
