Anaerobic energy metabolism of the scavenging isopodCirolana borealis (Lilljeborg)

Summary

• 1. Cirolana borealis utilises glycogen during anaerobiosis and shows a marked Pasteur effect. In 18h, 20–30 mg/g dry weight were converted, about half of the initial total glycogen content (Table 1).

• 2. Lactate is the major end product, while succinate and alanine are minor end products. 27–52% of the lactate produced was excreted into the incubation water (Tables 2 and 3). A good stoichiometric relationship was obtained between the glycogen consumed and the accumulation of these end products.

• 3. Small amounts of glutamate and aspartate contribute to the carbon flow, which could be of significance for obtaining redox balance (Table 3).

• 4. ATP production during anoxia was 75% of that during the standard aerobic state.

• 5. It is concluded that anaerobic fermentative metabolism ofC. borealis is adapted to maintain a high ATP output per unit time, which suits the high energy demand under natural anaerobic conditions.

• 6. WhenC. borealis are subjected to experimental anoxia they expel their gut contents and the incubation water becomes enriched with acetate, propionate, and amino acids. Most of these compounds probably stem directly from the gut content, while some, like acetate, may be produced by microbial activity. Starvation and anaerobic preincubation resulted in a marked lowering of the amounts of these compounds in the incubation water.