Physiological And Biochemical Aspects Of The Valve Snap And Valve Closure Responses In The Giant Scallop Placopecten-Magellanicus .1. Physiology

1. Catabolic processes of the phasic and catch parts of the adductor muscle ofPlacopecten magellanicus have been studied in relation to valve snap and valve closure responses. It is concluded that the snap response is powered by both parts of the adductor muscle and the valve closure response is powered exclusively by the catch part. 2. Both parts of the adductor muscle show a high glycolytic potential, reflected by high levels of glycolytic enzymes (Table 1) and high glycogen levels (Table 2). Lactate dehydrogenase could not be detected. In contrast, octopine dehydrogenase shows high activities in both parts of the adductor muscle. It is therefore concluded that a main anaerobic pathway in both tissues is the breakdown of glycogen to octopine. In the catch part, however, a considerable amount of the pyruvate formed from glycogen may also be converted into alanine (see below). The glycolytic flux in the catch part is much higher during the snap response than during valve closure. 3. The absence of phosphoenolpyruvate carboxykinase in the adductor muscle ofP. magellanicus and the observed changes in aspartate, alanine and succinate demonstrate that the energy metabolism in the catch part during valve closure shows great similarities to that which occurs only in the initial stage of anaerobiosis in the catch adductor muscle of the sea musselMytilus edulis L. 4. Arginine kinase activity and arginine phosphate content of the phasic part are much higher than those of the catch part (Tables 1 and 3). This may explain why in the phasic part during the snap response most ATP equivalents are derived from arginine phosphate, and in the catch part during both valve responses most are derived from glycolysis (Table 6). Despite the limited contribution of glycolysis in the phasic part during the snap response, the glycolytic flux increases by a factor of at least 75. 5. Evidence is obtained that octopine is neither transported from one part of the adductor muscle to the other, nor from the adductor muscle to other tissues.

Physiological And Biochemical Aspects Of The Valve Snap And Valve Closure Responses In The Giant Scallop Placopecten-Magellanicus .2. Biochemistry

1. Catabolic processes of the phasic and catch parts of the adductor muscle ofPlacopecten magellanicus have been studied in relation to valve snap and valve closure responses. It is concluded that the snap response is powered by both parts of the adductor muscle and the valve closure response is powered exclusively by the catch part. 2. Both parts of the adductor muscle show a high glycolytic potential, reflected by high levels of glycolytic enzymes (Table 1) and high glycogen levels (Table 2). Lactate dehydrogenase could not be detected. In contrast, octopine dehydrogenase shows high activities in both parts of the adductor muscle. It is therefore concluded that a main anaerobic pathway in both tissues is the breakdown of glycogen to octopine. In the catch part, however, a considerable amount of the pyruvate formed from glycogen may also be converted into alanine (see below). The glycolytic flux in the catch part is much higher during the snap response than during valve closure. 3. The absence of phosphoenolpyruvate carboxykinase in the adductor muscle ofP. magellanicus and the observed changes in aspartate, alanine and succinate demonstrate that the energy metabolism in the catch part during valve closure shows great similarities to that which occurs only in the initial stage of anaerobiosis in the catch adductor muscle of the sea musselMytilus edulis L. 4. Arginine kinase activity and arginine phosphate content of the phasic part are much higher than those of the catch part (Tables 1 and 3). This may explain why in the phasic part during the snap response most ATP equivalents are derived from arginine phosphate, and in the catch part during both valve responses most are derived from glycolysis (Table 6). Despite the limited contribution of glycolysis in the phasic part during the snap response, the glycolytic flux increases by a factor of at least 75. 5. Evidence is obtained that octopine is neither transported from one part of the adductor muscle to the other, nor from the adductor muscle to other tissues.

Physiological And Biochemical Responses Of Bivalve Mollusks To Exposure To Air

1. Aerial rate of oxygen consumption by Mytilus edulis and M. galloprovincialis is 4–17% of the aquatic rate. 2. For Cardium edule and Modiolus demissus the aerial rate of oxygen uptake is between 28 and 78% of the aquatic rate. 3. These species differences are related to the degree of shell gape during air exposure. 4. All species show an apparent oxygen debt after exposure to air, the extent of which is not simply related to either the level of aerobic respiration or the degree of anaerobiosis during exposure. 5. Anaerobic end-products accumulate in the tissues of Mytilus during aerial exposure, but not in Cardium. 6. The relative energy yields by aerobic and anaerobic means in M. edulis are discussed.

Responses Of Mytilus-Edulis L To Low Oxygen-Tension - Acclimation Of Rate Of Oxygen-Consumption

1. Mytilus edulis acclimated its rates of oxygen consumption when maintained at reduced oxygen tensions for periods in excess of five days. 2. Acclimation was complete down to approximately 55 mm Hg PO2 at slightly lower oxygen tensions (51, 49 and 43 mm Hg) acclimation was complete in one experiment and partial in two others. 3. The capacity to acclimate oxygen consumption was not affected by a reduction in ration nor by an increase in temperature (10 to 22 °C). 4. Mussels that were acclimated to reduced oxygen tension (40–80 mm Hg), and then exposed to P O 2 of less than 20 mm Hg for two or five hours, had depressed rates of oxygen uptake when subsequently “recovered” to 40–80 mm Hg. 5. These results are discussed in the context of biochemical studies of anaerobic metabolism in mussels from the same experiments.