symbionts from these lucinids use aerobic respiration, which
seems likely.
During periods of anoxia, sulfide is present in seawater medium
containing both C. orbicularis and its purified bacteria.
Previous attempts to demonstrate sulfide production by purified
symbionts from L. aequizonata have failed (3), and the
production was speculated to originate from either L. aequizonata
or its intracellular symbionts (3). The hydrogen sulfide
generated in the purified symbiont preparations from C. orbicularis
was measured directly with microelectrodes submerged
into the suspensions. From these measurements, it is evident
that the symbiont, and not the clam, is the source of the sulfide.
Sulfide was produced only in live symbiont suspensions while
medium containing heat-killed or poisoned symbionts did not
contain hydrogen sulfide. These data indicate that some metabolic
product or process is involved in the liberation of sulfide