The main diff erencesof fish muscle as compared -with muscle of land ani- 

 mals are lower glycogen content, initially higher lactic acid content, 

 and greater ATP-ase activity (Hamoir 1955 b), Steinbach (19U9) compared 

 ATP-ase activity of muscle-tissue homogenates of swordtail, bluegill, 

 minnow, frog, turtle, mouse, and bird. Measured at 30° C., ATP is split 

 at nearly the same rate by all the homogenates, but at 0° C, wide differ— 

 ences occur, with the activity of the fish preparations remaining fairly 

 high. Based on the Qio values obtained, the animals fell into three groups? 

 fish, l.U-1.7, bird, mouse, and turtle, 2.0; and frog, intermediate. The 

 relative insensitivity of fish ATP-ase to changes in temperature suggests 

 that low Qio values for critical reactions may be an adaption of cold-blooded 

 animals that must survive variable temperatures. Apparently, however, 

 no correlation exists relating ability to survive in cold temperatures 

 with Qio values, since the turtle, minnow, frog, and bluegill all can live 

 at cold temperatures, whereas fish from warmer water (for example, sword- 

 tail) can withstand only a very small decrease in temperature. Davidson 

 and Richards (195U) have calculated activation energies for muscle ATP-ase 

 of the crayfish, minnow, and cockroach. At low temperature, the quantit- 

 ative level of ATP-ase activities is in the same order as is the activity 

 of the whole animal in nature. They suggested that ATP-ase activity could 

 be a limiting factor governing activity of these species. 



Glycolysis in the oyster has been given considerable attention. As 

 with fish, general composition (fat, protein, and carbohydrate) of this 

 marine invertebrate has been studied (Lee and Pepper 1956). Humphrey (1950 

 b), working with vitreous and nacreous muscle homogenates and extracts of 

 the oyster, demonstrated pyruvic and lactic acid formation from glycogen, 

 glucose, glucose-l-phosr>hate, glucose-6-phosphate, and fructose-l,6-diphos- 

 phate added as substrates. He stated that the following intermediates 

 associated with glycolysis were present: ATP, ADP, glucose-1-phosphate, 

 glucose-6-phosphate, fructose-6-phosphate, fructose-l,6-diphosphate, triose 

 phosphate, phosphoglyceric acid, and phosphopyruvic acid. In addition, 

 both vitreous and nacreous muscle are able to synthesize glucose-6-phos- 

 phate from glucose-1-thosphate and, in the opposite direction, glycogen 

 from glucose- l-Dhost)hate. The formation of fructose-6-phosphate and fruc- 

 tose-l,6-diphosphate from glucose-6-phosphate also occurs. The glycolytic 

 ability of oyster muscle is several hundred times less powerful than is 

 that of rabbit muscle. It may be that glycolysis in the oyster is a slow, 

 continuous process in contrast to glycolysis in ma m mals, where glycolytic 

 activity is temporary and is brought into operation after muscular contrac- 

 tion (Humphrey 19 50 b). Usuki (1956) investigated the effect of the inhib- 

 itors of glycolysis — iodoacetic acid and sodium fluoride — on the activity 

 of oyster gills. The suppression of ciliary action that occurs can be 

 overcome oartially by addition of pyruvate and succinate, but not by ad- 

 dition of" glucose. This fact suggests that the Qabden-Meyerhof pathway 

 is blocked by these inhibitors. 



Also studying the effects of inhibitors, Humphrey (1950 a) demon- 

 strated a decrease in respiration of oyster spermatozoa upon treatment 

 with sulfhydryl-group reactants, such as iodoacetate and phenylmercuric 

 acetate. Compared to glycolytic rates of the sperm of land animals, how- 

 ever, the glycolytic rates observed are very low, as was shown by the 

 limited production of lactic acid from the breakdown of various hexoses 

 that were added as substrates. Since consumption of oxygen is higher than 



