Studies on Pigmented Microorganisms From Aphotic Marine Environments. Iii. Evidence of Apparent Utilization by Benthic and Pelagic Tunicata1

Over a 4‐month period 158 colonies of the pelagic tunicate Pyrosoma plus one large salp were trawled from depths between the surface and 750 m in an area to the southwest of the island of Oahu in the subtropical Pacific. Examination of individual zooid gut contents, by light and electron microscopy, revealed the presence of the so‐called olive‐green cells. These cells were abundant in all organisms examined except those from the euphotic zone. Examination of the gut contents of a benthic tunicate collected from 1,500 m in the Indian Ocean also revealed the presence of large numbers of these cells. This is the first direct evidence that olive‐green cells are undergoing significant removal by marine organisms