Karun Thongprajukaew

Smart phone: A popular device supports amylase activity assay in fisheries research

Colourimetric determinations of amylase activity were developed based on a standard dinitrosalicylic acid (DNS) staining method, using maltose as the analyte. Intensities and absorbances of red, green and blue (RGB) were obtained with iPhone imaging and Adobe Photoshop image analysis. Correlation of green and analyte concentrations was highly significant, and the accuracy of the developed method was excellent in analytical performance. The common iPhone has sufficient imaging ability for accurate quantification of maltose concentrations. Detection limits, sensitivity and linearity were comparable to a spectrophotometric method, but provided better inter-day precision. In quantifying amylase specific activity from a commercial source (P>0.02) and fish samples (P>0.05), differences compared with spectrophotometric measurements were not significant. We have demonstrated that iPhone imaging with image analysis in Adobe Photoshop has potential for field and laboratory studies of amylase.

Effects of sex on characteristics and expression levels of digestive enzymes in the adult guppy Poecilia reticulata

BackgroundCharacteristics (pH 2 to 12 and temperature of 25°C to 80°C) and expression levels of the main digestive enzymes, including amylase, lipase, total protease, trypsin, and chymotrypsin, were investigated in adult male and female guppies Poecilia reticulata. A completely randomized design was used during this experiment.ResultsDigestive enzyme studies indicated that sex had a direct effect on characteristic profiles (n = 3) and expression levels (n = 10) of all digestive enzymes. The most suitable conditions for studying digestive enzymes in general were pH 2 at 50°C for acidic amylase, pH 7 at 55°C for neutral amylase, pH 11 at 50°C for alkaline amylase, pH 7 at 30°C to 35°C for lipase, pH 2 at 55°C for acidic protease, pH 9 at 45°C for alkaline protease, pH 8 at 50°C for trypsin, and pH 9 at 50°C for chymotrypsin, regardless of sex. Specific activities of amylase, total protease, trypsin, and chymotrypsin were higher in females than males (p < 0.001), while the specific activity of lipase was higher in males than females. These findings were correlated with the higher growth capacity of females than males (except for lipase), as indicated by differences in body weight (p < 0.001), length (p < 0.001), and the activity ratio of trypsin (T) to chymotrypsin (C), i.e., the T/C ratio (p < 0.007).ConclusionsFeeding habits of adult guppies differed between sexes, as indicated by a difference in the activity ratio between amylase and trypsin, i.e., the A/T ratio (p < 0.04). Information from digestive enzyme studies, as well as using optimal conditions of digestive enzymes to study in vitro nutrient utilization in guppies, might be important to understand the effects of sex on nutritional responses.

Physical modification of palm kernel meal improved available carbohydrate, physicochemical properties and in vitro digestibility in economic freshwater fish

BACKGROUND Unavailable carbohydrates are an important limiting factor for utilization of palm kernel meal (PKM) as aquafeed ingredients. The aim of this study was to improve available carbohydrate from PKM. Different physical modifications including water soaking, microwave irradiation, gamma irradiation and electron beam, were investigated in relation to chemical composition, physicochemical properties and in vitro carbohydrate digestibility using digestive enzymes from economic freshwater fish. RESULTS Modified methods had significant (P < 0.05) effects on chemical composition by decreasing crude fiber and increasing available carbohydrates. Improvements in physicochemical properties of PKM, such as water solubility, microstructure, relative crystallinity and lignocellulosic spectra, were mainly achieved by soaking and microwave irradiation. Carbohydrate digestibility varied among the physical modifications tested (P < 0.05) and three fish species had different abilities to digest PKM. Soaking was the appropriate modification for increasing carbohydrate digestion specifically in Nile tilapia (Oreochromis niloticus), whereas either soaking or microwave irradiation was effective for striped snakehead (Channa striata). For walking catfish (Clarias batrachus), carbohydrate digestibility was similar among raw, soaked and microwave-irradiated PKM. CONCLUSION These findings suggest that soaking and microwave irradiation could be practical methods for altering appropriate physicochemical properties of PKM as well as increasing carbohydrate digestibility in select economic freshwater fish.

Ecological Effects on Food Utilization, Trypsin Isozymes, and Performance Qualities of Growth and Maturation in Northeast Arctic Cod (Gadus morhua L.)

The work demonstrates, for the first time, natural biological changes in fish during maturing processes using a unique combination of different biochemical techniques. Northeast Arctic cod caught by demersal trawls were studied in three Barents Sea areas during February-March 2008. Older larger cod from area A (between North Kanin Bank and Eastern Basin) had higher food utilization efficiency (with females showing highest white muscle protein synthesis capacity) than those from areas B (Kanin Bank) and C (Central Bank). Populations in areas A and C living in separate environments showed parallel regressions of pyloric caecal slope T/C ratio, with different elevations of trypsin specific activities and trypsin isozymes expressions. Approximately 30 trypsin isozymes were observed, with 13 isozymes of possibly exogenous trypsin isozyme fragments from prey items found at higher percentage of cod in areas A and B with higher food varieties. Larger maturing cod required higher energy from carbohydrate (probably phytoplankton), as amylase specific activity correlated with body weight. White muscle RNA levels were varied among females from different areas, but not among males. RNA and RNA/protein ratio levels were higher in oocytes than white muscle, and these levels decreased in higher developed oocytes. Oocyte trypsin-like specific activity in areas B A > C) illustrated that females from area B (youngest with lowest oocyte protein turnover) had highest maturation rate, and would reach their spawning area(s) before those from areas A and C. Younger females (probably also males) living closer to coastal area with higher temperature and food varieties would reach sexual maturity faster than older cod and those living far from coastal area.

Optimal‐rearing density for head‐starting green turtles (Chelonia mydas Linnaeus, 1758)

While ex situ conservation programs of juvenile green turtles (Chelonia mydas Linnaeus, 1758), before release to natural habitats, have been conducted in several countries, the optimal-stocking density for husbandry has not yet been reported. The optimization of stocking density was the main purpose of this study. The 15-day-old post-hatching turtles (29.30 ± 0.05 g body weight) were reared in round fiberglass tanks at various stocking densities including 20 turtles/m3 (20TM), 40 turtles/m3 (40TM), 60 turtles/m3 (60TM), and 80 turtles/m3 (80TM), over an 8-week trial. Water quality, survival, growth performance, feed utilization, aggressive behavior, fecal digestive enzymes, and hematological parameters were compared between the treatments, and were used as indicators of a successful captive rearing program. The water quality across the four treatments was in the standard range, but a high-stocking density reduced the quality significantly. No mortality was observed in any treatment group. Superior growth and feed utilization were only observed with the 40TM treatment, relative to the others (P < 0.05). The turtles in this group had no aggressive behavior, as indicated by observing hind limb biting. This treatment manipulated the level of proteolytic activity of pepsin and trypsin in response to density stressor, but not amylase, lipase, and chymotrypsin. The 40TM treatment also maintained the hematological characteristics, indicating no negative effects on health status. Overall, the findings indicate that the captivity program of post-hatching turtles at 40 turtles/m3 is the preferred option in their head-started propagation, as well as in public displays in zoos or aquaria. Zoo Biol. 35:454-461, 2016.

Gastrointestinal Functionality of Aquatic Animal (Oreochromis niloticus) Carcass in Water Allows Estimating Time of Death

Postmortem changes have been previously studied in some terrestrial animal models, but no prior information is available on aquatic species. Gastrointestinal functionality was investigated in terms of indices, protein concentration, digestive enzyme activity, and scavenging activity, in an aquatic animal model, Nile tilapia, to assess the postmortem changes. Dead fish were floated indoors, and samples were collected within 48 h after death. Stomasomatic index decreased with postmortem time and correlated positively with protein, pepsin‐specific activity, and stomach scavenging activity. Also intestosomatic index decreased significantly and correlated positively with protein, specific activity of trypsin, chymotrypsin, amylase, lipase, and intestinal scavenging activity. In their postmortem changes, the digestive enzymes exhibited earlier lipid degradation than carbohydrate or protein. The intestine changed more rapidly than the stomach. The findings suggest that the postmortem changes of gastrointestinal functionality can serve as primary data for the estimation of time of death of an aquatic animal.

Identification of wild and farmed broadhead catfish ( Clarias macrocephalus Günther, 1864) based on morphometry, digestive indexes and flesh quality

Wild and farmed fish generally differ in their nutritional composition. In this study, adult wild and farmed broadhead catfish ( Clarias macrocephalus Günther, 1864) were collected and were assessed for various characteristics, namely morphometrics, digestive indexes, and flesh quality. The morphometrics (standard length, body depth, eye width, fin height and tentacle length) and the digestive indexes (intestosomatic index, digestosomatic index, perivisceral fat index and activities of pepsin and lipase) differed significantly between the groups ( P <0.05) and can be used to distinguish wild fish from farmed fish. In terms of protein synthesis capacity and color, the flesh quality was similar between the groups. However, radical scavenging activities and reducing power were significantly higher in the wild fish than in the farmraised group. The thermal transition characteristics of sarcoplasmic proteins, as well as myosin denaturation enthalpy and fatty acid profiles (C18:2 n 6, C20:0, C22:1 n 9, C24:0, Σpolyunsaturated fatty acids, and Σ n-6) also exhibited potential to enable calls about the fish origin. The proximate chemical composition of whole body did not differ between the two fish populations. Our findings suggest bioindicators, in terms of morphometrics, digestive indexes and flesh quality, that can be used to identify the origin of fish for forensic purposes, of for conservation biology of this near threatened species. The new nutritional information may be of interest to marketing, consumers, and has a connection to nutritional effects on human health.