The Concentrations of Proteases, Amylase, and Lipase in Certain Marine Fishes

Marine fishes show great diversity as to food, feeding habits, special habitat, and rate and type of metabolism. Some have predominantly a fatty metabolism while others have essentially a carbohydrate metabo lism in the sense that the nutritive reserves are stored in the form of fat or carbohydrates. Certain fishes, such as the mackerel, are ex tremely active; others are very sluggish; still others represent all the intergrades. Great variation is shown as to the development of the differentorgans concerned with digestion;in some fishesthe pancreas is more or less clearly defined, in others it is diffuse and may be partially included in the liver. Pyloric c@ca, which are the embryological equiv alent of the exocrine pancreas, may also be its physiological equivalent in some cases. These structures are absent in many fishes. As these factors vary, it is to be expected that there will be adaptive variations in the amounts and sites of production of the different di gestive enzymes secreted. It is the purpose of this investigation to determine where the enzymes are secreted, and in what quantities, with a view to making correlations with the anatomy and physiology of the fishes studied. The early literature bearing upon digestion in fishes is well reviewed by Yung (1899) and Sullivan (1907). The rate of digestion has been studied by Van Slyke and White (1911). They state that in the dogfish two to three days are required for the disposal of a meal; this is about six times as long as the period in mammals, which may be due to the temperature difference. Svolima (1919) found the period of digestion to last up to five days. Yung (1899) had set the period at ten hours. Kenyon (1925) compared digestion in the different classes of verte brates. Peptic digestion he found to be remarkably uniform among all the animals investigated, with the exception of the stomachless carp. Gastric acidity is exceedingly variable, apparently depending upon the functional state of the organ. There seems to be no correlation between peptic activity and food habits. There is a close correlation between the 133