Abstracts (Continue in Part XXXVII)

The highly active, muscular squid of the pelagic rely on jet propulsion for locomotion by means of mantle muscle contractions. Continuous mantle activity is required for ventilation and gas exchange. The metabolic rate of this high strung molluscan muscle is the highest reported for marine invertebrates, and is supported by a high content of mitochondria. It makes maximum use of available oxygen by not only exploiting blood oxygen transport but also by oxygen uptake via the skin (1). At the anaerobic threshold (reached at a critical swimming speed) anaerobic energy production starts simultaneously in the cytosol and in mitochondria indicating that oxygen supply to mitochondria becomes limiting (2). This finding is quite opposite to the situation found in many other invertebrate and vertebrate species, where energy requirements in excess of aerobic energy production are covered by anaerobic metabolism, with the mitochondria remaining aerobic. Octopine is the end product of anaerobic glycolysis in squids, the muscular phosphagen is phospho-L-arginine, which releases arginine into octopine formation during anaerobic contraction and supports the extension of activity beyond the critical speed (3): Phospho-L-arginine (PLA-) + MgADP+ H+ <=> L-Arginine (LArg+) + MgATP2-