Additional Insight into the Structure and Biology of Abyssotherma-Pacifica (Bronnimann, Vandover and Whittaker) from the East Pacific Rise

The surface of a newly described remaneicid foraminifer, Abyssotherma pacifica, contains agglutinated particles of obsidian. Beneath the umbilical surface of the test of the foraminifer is a loosely aggregated detrital mat through which large pseudopodal trunks emerge. The obsidian flakes were removed from the surface of the test by immersion of the foraminifera in HF for 12-18 hours. This permitted microtoming and further study by light and electron microscopy. The test has an electron dense inner organic lining approximately 0.5-mu-m thick which is overlain by a mesh of organic cement fibrils surrounding the obsidian particles. New chambers are added by accretion without decomposition of previous walls. Bacteria and unrecognizable materials were found in vacuoles which were presumably digestive vacuoles. Although we were searching for possible endosymbiotic chemolithotrophic bacteria, we found no evidence of the phenomenon due to the vent community context. The question was not completely resolved because the cell fine structure was not well-preserved by the fixation methods used during field collection.