Utilization of oxygen, glucose, and carbon dioxide by Echinorhynchus gadi

Specimens of the acanthocephalan, Echinorhynchus gadi, were taken from the gut of the winter flounder, Pseudopleuronectes americanus, caught by commercial fishermen off Point Judith, Rhode Island. In November, 18 of 32 fish examined contained parasites, and in March, 91 of 232. The worms were larger and more numerous in the fall. When first isolated, E. gadi consumed oxygen at 9.65 μmoles/g-hr at 25 C, and during 10 days of survival outside the host (at 5 C) the rate diminished to less than half the initial rate. Respiratory quotient, initially 0.78, rose in 2 days to near 1.0, and remained there. Oxygen consumption was unaffected by 0.002–0.200 m glucose, 0.120 m succinate, or 0.150 m alanine.Under nitrogen, the worms produced acid, which was measured as carbon dioxide released from a medium containing bicarbonate; the rate was 6.12 μmoles CO₂/g-hr. Addition of glucose (0.035 m) increased acid production 40%. Glucose-¹⁴C at 0.32 mm was taken up at an initial rate of 3.79 μmoles/g-hr; the label appeared in lactic acid, and in all six of the citric acid cycle intermediates examined. After incubation with glucose-¹⁴C for 3 hr, worms that were kept 12 hr. in aerated medium excreted labeled lactic acid almost exclusively, while those kept anaerobically produced nearly equal amounts of labeled succinic and lactic acids.Carbon dioxide fixation into succinic and other acids was demonstrated with labeled bicarbonate. Carbon dioxide fixation rates increased with total bicarbonate concentration of the medium, to a maximum of 1.20 μmoles CO₂/g-hr at 14.7 mm bicarbonate, or 12.5% of the O₂ consumption rate of freshly isolated worms. No uptake of aspartic acid was detected in 4 hr.