Untersuchungen zur Frühontogenie vonNautilus pompilius (Linné)

Abstract

A series of initial shells ofNautilus pompilius was investigated for morphologic and isotopic evidence of the early ontogenetic development. Shell morphologic features, such as curvature of early shell, cancellate sculpture, suture and grouping of septa, as well as very early shell injuries, color banding and shell/egg dimensions, seem to indicate an interpretation of early ontogeny differing from that which is now generally accepted. The O18/O16 and C13/C12 ratios in the early shell and septa of twoNautilus specimens are given. Changes in the carbon isotope content are tentatively correlated with the end of the embryonic period and with environmental changes. Variations in the oxygen isotope content are in part ascribed to migrations from warm to cooler water after a certain stage of development. The size of the body chamber of the young animals can be determined by comparison of the isotope contents in outer shell and septa. Existing ideas concerning early ontogeny ofNautilus are critically discussed.