Shell Regeneration and Biological Recovery of Planktonic Foraminifera after Physical Injury Induced in Laboratory Culture

Abstract

Living specimens of Globigerinoides sacculifer (Brady) were subjected to varying degrees of damage in 2 series of experiments. In the first 3-group experiment, one, two or all chambers of the shells were crushed, whereas in the second 3-group experiment, successive chambers were amputated from the shells. The purpose of both sets of experiments was to determine the relative rate of recovery of and mode of shell regeneration by the injured organisms. The great majority in 5 of the 6 groups recovered and continued shell growth by regenerating spines, cementing broken parts, adding new chambers and undergoing gametogenesis. The shell shapes which resulted from the crushed specimens were generally bizarre, whereas the amputated specimens regrew chambers of normal shape. The nucleus in adult G. sacculifer shells appears to be located in the F-3 or earlier chamber. Our experiments indicate that in spite of severe injury to the shell, these tenacious marine protozoans can generally restore their biological functions of calcification, predation, symbiosis with algae, and gametogenesis. In nature, abnormal shells which show evidence of physical damage are most likely caused by predators; thus their frequency reflects a relative predation pressure on planktonic foraminifera.