Putting the Pacific fat sleeper Dormitator latifrons (Pisces: Eleotridae) to sleep: effects of clove oil and lidocaine anesthetic.

Among the different handling techniques in aquaculture, the use of anesthetics has had a growing interest focused on guaranteeing animal welfare, and reducing possible stress situations during general handling. The aim of this study was to present the use of eugenol and lidocaine with non-invasive anesthesia procedures in Dormitator latifrons, in which the different stages of anesthesia (induction and recovery) were determined. One hundred and twenty healthy fish of average weight of 73.59 ± 13.53 g and standard length of 17 ± 1.36 cm were used. The experimental fish were subjected to fasting for 24 h prior to the tests. Five fish were subjected to eugenol (25, 50, 100, and 200 µL/L), and lidocaine (100, 200, 300, and 400 mg/L), in triplicate. The time to reach deep and recovery anesthesia were recorded and the data analyzed using ANOVA (α= 0.05). Organisms exposed to anesthetics evidenced early episodes of fast, short-distance swimming (initial hyperactivity) for short periods of time. Survival was 100% with both compounds and concentrations. Fish exposed to a eugenol concentration of 200 µL/L had longer anesthesia times and took longer time to recover (P<0.05). The most effective concentrations for eugenol and lidocaine were of 200 µL/L and 400 µL/L in juvenile fish, promoting rapid inductions, without compromising the conditions for the recovery of the fish. This work provides practical information for handling and transportation D. latiforns with the least possible stress and ensuring animal welfare.

Lipase and Phospholipase Activity Methods for Marine Organisms.

Lipases are very important enzymes having a role in fat digestion and lipid metabolism in marine animals, plants, and microorganisms. The methods for measuring lipase and phospholipase activity have been applied in several studies; however, considering that lipases are water-soluble molecules and their substrates are generally water-insoluble molecules, several steps are required for measuring their digestion products. After a general review of the main type of methods used in marine lipase studies, and experimental procedures, a proposal of new or improved methods is described in order to facilitate the lipase activity measurements in marine organisms.

Development of digestive tract and enzyme activities during the early ontogeny of the tropical gar Atractosteus tropicus.

Changes in digestive enzyme activity and histology were studied in Atractosteus tropicus embryos, larvae and juvenile periods. Alkaline protease, chymotrypsin, carboxypeptidase A, lipase and α-amylase were detected in all periods and gradually increased until reaching the maximum peak in juveniles; meanwhile, acid protease was first detected at 5 days after hatching (dah) when first feeding started and trypsin and leucine aminopeptidase activities were detected from 19 dah, their values being increased gradually until reaching a maximum value at 31 dah. Acid and alkaline phosphatase activities increased from yolk-sac absorption (3 dah) until day 31 after hatching. Zymogram for acid protease showed two bands in active forms (0.4 and 0.5 Rfs) from day 5 after hatching and a third protease form (0.3 Rf) that appears at 31 dah. Two active forms (26.3 and 24.9 kDa) were detected using SDS-PAGE alkaline proteases zymogram at 5 dah, and an additional active form (44.1 kDa) was detected at 7 dah. Regarding the histological development of the digestive system, the exocrine pancreas containing zymogen granules was already visible at 3 dah, whereas at 5 dah first gastric glands were already detected in the stomach. Between 7 and 9 dah, the digestive tract of A. tropicus resembled that of a juvenile specimen with a well-developed and short oesophagus, stomach divided into a glandular and non-glandular (pyloric) stomach, folded intestine with pyloric caeca and a well-developed spiral valve (posterior intestine). Considering this, larvae of A. tropicus are capable of digesting several foods from yolk absorption (3 dah), maximizing its activities at 15 dah, age at which the organisms maximize its capability to absorb nutrients from diets provided.

Development of digestive enzyme activity in spotted rose snapper, Lutjanus guttatus (Steindachner, 1869) larvae.

We describe digestive enzyme activity during the larval development of spotted rose snapper, Lutjanus guttatus. Trypsin, chymotrypsin, leucine aminopeptidase, pepsin, amylase, lipase, and acid and alkaline phosphatase activities were evaluated using spectrophotometric techniques from hatching through 30 days. The spotted rose snapper larvae present the same pattern of digestive enzyme activity previously reported for other species in which pancreatic (i.e., trypsin, chymotrypsin, amylase, and lipase) and intestinal (i.e., acid and alkaline phosphatases and leucine aminopeptidase) enzymatic activities are present from hatching allowing the larvae to digest and absorb nutrients in the yolk-sac and live prey by the time of first feeding. The digestive and absorption capacity of the spotted rose snapper increases during the larval development. A significant increase in individual activity of all enzymes occurs at 20 DAH, and around 25 DAH, the juvenile-type of digestion is observed with the appearance of pepsin secreted by the stomach, suggesting that maturation of the digestive function occurs around 20-25 DAH. Our results are in agreement with a previous suggestion that early weaning may be possible from 20 DAH. However, the patterns of enzymatic activities reported in our study should be considered during the formulation of an artificial diet for early weaning of the spotted rose snapper.

Partial characterisation of digestive proteases of the Mayan cichlid Cichlasoma urophthalmus.

The characterisation of digestive proteases in native freshwater fish such as the Mayan cichlid Cichlasoma urophthalmus provides scientific elements that may be used to design balanced feed that matches with the digestive capacity of the fish. The purpose of this study was to characterise the digestive proteases, including the effect of the pH and the temperature on enzyme activity and stability, as well as the effect of inhibitors using multienzymatic extracts of the stomach and intestine of C. urophthalmus juveniles. Results showed that the optimum activities of the acid and alkaline proteases occurred at pH values of 3 and 9, respectively, whereas their optimum temperatures were 55 and 65 °C, respectively. The acid proteases were most stable at pH values of 2­3 and at temperatures of 35­45 °C, whereas the alkaline proteases were most stable at pH values of 6­9 and at 25­55 °C. The inhibition assays recorded a residual activity of 4% with pepstatin A for the acid proteases. The inhibition of the alkaline proteases was greater than 80% with TPCK, TLCK, EDTA and ovalbumin, and of 60 and 43.8% with PMSF and SBT1, respectively. The results obtained in this study make it possible to state that C. urophthalmus has a sufficiently complete digestive enzyme machinery to degrade food items characteristic of an omnivorous fish species, although specimens showed a tendency to carnivory.

Development of digestive enzyme activity in larvae of spotted sand bass Paralabrax maculatofasciatus II: Electrophoretic analysis.

The activities of several digestive enzymes during larval development of the spotted sand bass (Paralabrax maculatofasciatus) were evaluated using electrophoretic techniques. The results show the presence of three isoforms of alkaline protease from day 2 after hatching (ah) and the early appearance of one pepsin-like band from day 12 ah onwards. In addition, two lipase bands first appeared on day 2 ah, and there was a change in the molecular weight of one band from day 15 ah onwards. Several alpha-amylase isoforms were observed from hatching up to day 5 ah. These results indicate that the important digestive enzymes develop rapidly in these larvae, supporting the possibility of early weaning at day 12 ah using artificial diets.