Membrane digestion in freshwater fish species has been extensively studied [1, 8-10, 12, 13, 17, and many others]. The intestinal digestive enzymes of sea fishes have been investigated less thoroughly [3,6,7,11,22], and virtually no studies have investigated fishes of the Far Eastern seas in this aspect.Gawlicka et al. revealed the activity of trypsin, amylase, lipase, and alkaline phosphatase in the yolk-sac larvae of the Atlantic halibut Hippoglossus hippoglossus (Linnaeus, 1758) and showed that enzymatic activity increased with the age of larvae [24]. Similarly, Ribeiro et al. have demonstrated that the larvae of Solea senegalensis Kaup, 1858 are capable of full digestion of food a month after hatching as a result of the increasing activity of acid and alkaline phosphatase, lipase, and aminopeptidase in the larval digestive tract [25, 26]. Study of adult Platichthys flesus luscus (Pallas, 1811) from the Black Sea [11] has demonstrated a high level of total amylolytic activity [2.95 ± 0.35 µ mole/(min g)] and low values of total proteolytic and sucrose activity [0.48 ± 0.13 and 0.44 ± 0.08 µ mole/(min g), respectively] in the intestinal mucous membrane.This paper focuses on study of the activity and temperature dependence of the chief digestive enzymes in the intestine of the Pacific halibut and starry flounder inhabiting the Far Eastern seas.
MATERIALS AND METHODSStudies were carried out in 2002-2003 by the Kamchatka Research Institute for Fisheries and Oceanography and by Astrakhan State Technical University. Ten specimens of Pacific halibut (length 41-51 cm, weight 0.9-1.66 kg) and 10 specimens of starry flounder (length 26-33 cm, weight 100-500 g) were investigated. Pacific halibut were caught with a bottom trawl in October 2002 in Olyutorsky Bay at a 64-m depth. Starry flounder were captured with a beach seine in July 2003 in Avachinskaya Bay at A 2-to 4-m depth.Immediately after capture, fish were immobilized and morphometry was made. The intestine (without pyloric ceca) was taken out and washed with 20 ml of a cooled Ringer's solution for cold-blooded animals (pH 7.3) to remove its contents and cavity enzymes. The intestines were placed on a cooled glass, cleansed of fat, measured, and weighed. Material was then frozen at -18 to -20 ° C in a thermos and stored until experimentation. After thawing, the intestine mucous membrane was removed using a scraper, weighed on a VT-500 torsion balance, and homogenized in a cooled (0 − 3 ° C) Ringer's solution (1 : 9) on a RT-1 homogenizer with a Teflon piston. The resultant homogenate was then diluted with Ringer's solution to determine the linear enzymatic activity.
FISH PHYSIOLOGYAbstract -The activity and temperature characteristics of hydrolases (maltase, α -amylase, total proteinase, alkaline phosphatase) in the intestine of Far Eastern flatfishes were studied. The character of the temperature dependence differed among the investigated enzymes. The activity of individual hydrolases in the two fish species varied. The results of this study suggest that flatfish...