Growth and Longevity of Nautilus

Abstract

Like many other aspects of the life history of Nautilus, its rate of growth and longevity have until recently been unknown. Growth rate is defined as the increase in dimensions of the shell or number of septa (chambers) with respect to time. The growth of the shell involves two processes: (1) Shell is accreted at the aperture in conjunction with growth of the soft body; as traced along the venter, the shell forms a logarithmic spiral in which radial increase is an exponential function of rotational angle. (2) Periodically, the animal moves forward to begin formation of a new septum (chamber) at the rear of the body chamber (see Chapter 34, this volume). Except near maturity and immediately after hatching, septa are usually secreted at equal angular intervals and the ratio of chamber volumes between adjacent chambers is constant.