Respiration and Photosynthesis Inconvoluta Roscoffensisgraff, Infected With Various Symbionts

Measurements of oxygen balance were made with a recording polarographic electrode on 3 strains of worms reinfected with several natural and unnatural symbionts. 1. The photosynthesis/respiration (P/R) ratios and net photosynthesis varied with light intensity but were independent of worm strains or algal species: compensation light intensities were also similar. 2. However, the content in chlorophyll a/mm3 of worm varied and in worms reinfected with unnatural symbionts was ⅓-½ that found in natural symbiont reinfected worm. Consequently, worms with unnatural symbionts produced more O2/µg chlorophyll a. 3. Cell size of different species of symbiont varied but average chl. a/cell was similar. Observations in vivo and with thick and thin EM sections showed that the number of symbionts/mm3 worm varied with symbiont species. Natural symbionts were more numerous, and more densely packed in superimposed tiers, mutual shading may be responsible for a less efficient photosynthesis. 4. However, adaptation to laboratory light intensities and the assumption implicit in the measurements and calculations of the P/R that dark respiration is equal to photorespiration may also account for the uniformity of results with different symbionts. 5. The P/R ratios appear to be an insensitive way to distinguish obligatory from faculitative symbionts. At best, positive P/R ratios indicate that excess photosynthate is produced but it does not indicate whether or not the photosynthate is released, taken up and/or utilized by the host, nor its nutritional contribution.