Biochemical interactions between the symbionts of Convoluta roscoffensis

Abstract

Convoluta will slowly eject most of their algae if CO 2 is bubbled through their seawater media for a brief preliminary period. By means of this technique, it was shown that at least half of the carbon fixed in photosynthesis moved from alga to animal, possibly in the form of amino acids. Dichlorophenyldimethyl urea completely inhibits photosynthesis in intact worms, but causes no other immediate damage to the animals. No uric acid can be detected in healthy animals, but it accumulates after 2 weeks’ incubation in DCMU. Uricase and glutamine synthetase are both detectable in worms, and it is suggested that ammonia produced by uric acid catabolism in algae is assimilated into glutamine, which may be the main amino acid released back to the animal. If animals are first labelled with a pulse of 14 C through photosynthesis and then transferred to nonradioactive seawater containing 1 g/100 ml alanine, the amount of fixed 14 C released from worms is increased by darkness or DCMU treatment with much of the released 14 C appearing in lactic acid; these effects are largely abolished if excess oxygen is supplied to the worms. This suggests that photosynthetically produced oxygen may be utilized by animals, but since they survived 4 weeks in DCMU, it was clearly not essential.