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Digestive Enzymes of the Developing Sepia pharaonis Ehrenberg 1831 Paralarvae
Get PDFIn order to understand the digestive physiology of Sepia pharaonis Ehrenberg 1831 (Sepiidae) paralarvae, and to formulate appropriate feeding strategies, the activity patterns of major digestive enzymes in relation to larval development were investigated. Trypsin, leucine aminopeptidase, alkaline phosphatase, alpha-amylase, and lipase were analyzed for 25 days from hatching. Results revealed that all digestive enzymes were present even prior to exogenous feeding, and each enzyme exhibited a distinct activity pattern. Leucine aminopeptidase, an enzyme involved in intracellular digestion, was found to be dominant and highly active at early developmental stages and declined with larval maturation. Lipase activity, involved in lipid metabolism, increased in the early stages of development but declined 10 days after hatching (DAH). Secreted enzymes (trypsin and amylase) and alkaline phosphatase (an indicator of larval gut maturity) exhibited low activity prior to 10 DAH and 13 DAH, respectively. However, these enzymes became highly active in the late developmental stages. These findings suggest the gradual gut maturation of S. pharaonis based on intracellular and secreted enzyme activities. The findings also indicate that paralarvae after hatching are well-equipped with digestive enzymes necessary to digest complex food items, and that the larval gut matures 13 to 20 DAH
Effect of Sargassum oligocystum Hot-Water Extract on Innate Immune Response and Survival of Summer Flounder Paralichthys dentatus to Vibrio harveyi Challenge
Get PDFThe present study evaluated the effects of hot-water extract of a brown seaweed Sargassum oligocystum on the non-specific immune response and survival of summer flounder Paralichthys dentatus, to Vibrio harveyi bacterial challenge. Fish were either immersed in 100 or 500 mg/L or injected with 0.1 or 0.5 mg per fish of the hot-water extract. The innate humoral (lysozyme, plasma protein, bactericidal activity), cellular (respiratory burst, hematocrit), and disease resistance to Vibrio harveyi infection were determined. Results showed that all the experimental treatments either by injection or immersion, significantly enhanced respiratory burst activity and hematocrit values of the fish. In the experiment, all the treatments of hot-water extract significantly affected the lysozyme, plasma protein, and bactericidal activity of the experimental fish from days 1 to 5 after delivery. Following the bacterial challenge mortality decreased significantly in all treated groups. In summer flounder, administration of hot-water extract of S. oligocystum either by injection or immersion was found to be an immunoprophylactic for finfish aquaculture. The efficacy of using hot-water extract as a feed supplement or feed additive needs further examination
Ontogenetic Development of Digestive Enzymes in Orange-Spotted Grouper (Epinephelus coioides, Hamilton, 1822) Larvae
Get PDFThe digestive physiology of orange-spotted grouper (Epinephelus coioides) was studied by assessing the specific and total activities of alkaline phosphatase, amylase, lipase, chymotrypsin, and trypsin, from hatching to 34 days post-hatching (DPH). From the onset of exogenous feeding, total alkaline phosphatase, amylase, lipase, and chymotrypsin activity fluctuated then sharply increased from 18 to 34 DPH. In contrast to other enzymes, the specific and total activity of trypsin remained at a low level from 1-26 DPH, and reached the maximum on 30 DPH. Digestive enzymes activity indicated that orange-spotted grouper were able to digest proteins, lipids, and carbohydrates at an early developmental stage. Results from the present study will improve understanding of the ontogeny of orange-spotted grouper during the larval stage, and provide a guide to hatchery feeding of this economically important fish
Hafnia alvei: a Pathogen Causing Infectious Intussusception Syndrome (IIS) in Farmed Channel Catfish Ictalurus punctatus
Get PDFInfectious intussusception syndrome (IIS) is a serious problem, causing severe economic losses in farmed channel catfish Ictalurus punctatus. Limited information is available on Hafnia alvei as a causal agent for this disease. In this study, a virulent strain, temporarily named HN01, was isolated from diseased channel catfish suffering from infectious intussusception syndrome, and identified through phylogenetic analysis and phenotypic characteristics. A phylogenetic tree was constructed to examine isolate HN01 and compare it to other known isolates. Isolate HN01 has also been found to be susceptible to aminoglycosides, quinolones and sulfonamides drugs for veterinary use in aquaculture when screened against a range of common antibiotics. To the best of our knowledge, this is the first report of infectious intussusception syndrome caused by Hafnia alvei in farmed channel catfish
Substitution of Krill meal for Fish Meal in Feed for Russian Sturgeon, Acipenser gueldenstaedtii
Get PDFKrill meal (KM) is a potential feed ingredient that can replace fish meal (FM) in aquaculture. To better understand the efficacy of krill meal, a 200-day feeding trial was conducted with Russian sturgeons (Acipenser gueldenstaedtii). Four extruded diets in which KM replaced 0%, 10%, 20%, or 30% of FM in the formulation were fed to 481 g sturgeons for 200 d. Russian sturgeons that were fed diets containing KM grew as fast as or even better than fish fed with FM control diet. No differences were observed in terms of dorsal muscle composition in the fish fed with diets including KM and those fed with FM control diet. Meanwhile, the fluoride concentrations in the dorsal muscle, liver, and kidney, as well as swim bladder in all dietary groups were below detectable limit. In the gills, skin, vertebral bone and dorsal scutes, the fluoride content from the KM groups progressively increased with dietary fluoride concentration. In conclusion, KM can partially substitute for FM in the diets of Russian sturgeon without affecting normal growth performance
Molecular Cloning and Response to Water Temperature and Nutrient Manipulation of Insulin-like Growth Factor (IGF) Genes in Golden Pompano Trachinotus ovatus (Linnaeus 1758) Larvae
Get PDFIn this study, insulin-like growth factor I (IGF I) and IGF II in golden pompano larvae were cloned and analyzed. In the first trial, IGF expression during ontogeny of larvae in the first 18-days of their life was explored, and then the response of IGFs to water temperature (23, 26, and 29oC) on 12 day post hatching (DPH) and 18 DPH were compared. On 28 DPH, the response of IGFs to the manipulation of nutrients was evaluated. The expression of IGF I increased with the increase of fish age, and was not significantly affected by water temperature. The expression of IGF II was affected by water temperature on 12 DPH and 18 DPH. The expression of IGF II at 23oC was significantly higher than at 26oC and 29oC. The expression of IGFs in fish larvae on 28 DPH was not concomitant with nutrient manipulation. This study detected the gene expression of IGFs at the early stage of golden pompano larvae. The time dependent expression of IGF genes in fish larvae is important to understand the ontogenetic development and growth of fish larvae in early life
