EFFECTS OF GAMETOGENESIS ON TEST STRUCTURE AND DISSOLUTION OF SOME SPINOSE PLANKTONIC-FORAMINIFERA AND IMPLICATIONS FOR TEST PRESERVATION

The process of gametogenesis observed in six species of laboratory reared spinose planktonic foraminifera was accompanied by significant changes in the calcite test. All species resorbed their spines prior to gamete release. In addition, a calcite crust was subsequently secreted over the outside of the test in three of the species [Globigerinoides sacculifer (Brady),Globigerinoides conglobatus (Brady),Orbulina universa d'Orbigny], the test was decalcified in one species [Hastigerina pelagica (d'Orbigny)] and there was little or no calcite crust deposited on the test in two species [Globigerinella aequilateralis (Brady) andGlobigerinoides ruber d'Orbigny], although the test weights of at least one of these species (G. aequilateralis) were greater in gametogenic specimens. Gametogenic calcification resulted in greater test weight per unit length and slower dissolution rates in laboratory experiments for gametogenic specimens depositing a calcite crust compared with specimens that did not undergo gametogenic calcification. Based on our results, we conclude that the species composition of planktonic foraminiferal test assemblages in deep-sea sediments is affected by whether or not the species undergo gametogenic calcification or decalcification, and the proportion of these specimens that have attained reproductive maturity in the overlying waters. © 1990 Elsevier Science Publishers B.V.