Reproduction was observed in adult specimens of Archaias angulatus, a large foraminiferan, collected when close to reproduction and maintained briefly in the laboratory until they reproduced. One sign that an individual was close to reproducing was the addition of a few to several empty new chambers. The protoplasm then migrated to these chambers and divided within them. This division within the adult test is comparable to Sorites orbiculus and in contrast to Heterostegina depressa, in which the protoplasm divides outside the test. After the young calcified, the outer walls of the final chambers broke apart and hundreds of young emerged as 2-chamber individuals containing symbionts. The walls of the final chambers and the apertural face on which they formed appeared to be resorbed, but earlier chambers remained intact. Thus, reproduction should not reduce the preservation potential of tests of Archaias angulatus, in contrast to some species of foraminifera in which most of the chamber walls are resorbed during reproduction. Chamber formation in Archaias angulatus was rarely observed, because all individuals accumulated detritus around the multiple apertures of the final chamber, which obscured the final chambers. When observed, chamber formation followed the pattern reported for other species of foraminifera. Initially, a dense mass of pseudopodia extended from the multiple apertures of the final chamber to form the shape of the new chamber. Thickening indicative of calcification occurred over the course of a few hours, at which time symbiont-bearing protoplasm moved into the new chamber. After three months, young from the clones that were cultured in the laboratory varied greatly in size. Within the same culture dish, some individuals were more than twice the size of others. More deformed tests were found among individuals cultured on a shaker table than among individuals from the same clones kept in static culture dishes. These differences in growth affect test strength and therefore preservation potential.

75/125 YEARS