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Observations on the growth rate of aquarium maintained Nautilus pompilius in different developmental stages, i.e. juveniles (shell length about 8.75 cm), late juveniles (approximately 10 cm), and early adolescent (approximately 13.5 cm), indicate that this species is fully grown at an age of 7.3-8 years. The age calculations are based on two different computations: (1) the measurement of the increase of the shell length per day and (2) the formation of new septa in time intervals of 150+/-5 days, as demonstrated by X-ray analyses. After N. pompilius hatches, its shell grows about 139 mm to reach full growth and approximately 28 septa are formed. With an increase of the shell length of 0.052 mm per day, it takes about 2,673 days (7.3 years) to reach maturity. Provided that the process of chamber formation follows an exponential function, these computations result in approximately 2,925 days (8 years) to reach full maturity. Supposing that N. pompilius may live for several years after onset of maturity like Nautilus belauensis, the total life span for this species may exceed 11-12 years.

Nine intraepithelial ciliated cell types that are presumed to be sensory cells were identified in the epithelium of the pre- and postocular tentacles, the digital tentacles, and the rhinophore of the juvenile tetrabranchiate cephalopod Nautilus pompilius L. The morphological diversity and specialization in distribution of the different ciliated cell types analyzed by SEM methods suggest that these cells include receptors of several sensory functions. Ciliated cell types in different organs that show similar surface features were combined in named groups. The most striking cell, type I, is characterized by a tuft of long and numerous cilia. The highest density of this cell type occurs in ciliary fields in the epithelium of the lamellae of the pre- and postocular tentacles, in the olfactory pits of the rhinophores, and in the lamellae of four pairs of lateral digital tentacles, but not in the epithelium of the medial digital tentacles. The similar morphological data, together with behavioral observations on feeding habits, suggest that this cell type may serve in long-distance chemosensory function. The other ciliated cell types are solitary cells with specific spatial distributions in the various organs. Cell types with tufts of relatively short, stiff cilia (types III, IV, VIII), which are distributed in the lateral and aboral areas of the tentacles and at the base of the tentacle-like process of the rhinophore, are considered to be employed in mechanosensory transduction, while the solitary cells with bristle-like cilia at the margin of the ciliary fields (type II) and at the base of the rhinophore (type IX) may be involved in chemoreception. Histological investigation of the epithelium and the nerve structures of the different organs shows the proportion and distribution of the sensory pathways. Two different types of digital tentacles can be distinguished according to their putative functions: lateral slender digital tentacles in four pairs, of which the lowermost are the so-called long digital tentacles, participate in distance chemoreception, and the medial digital tentacles, whose terminal axial nerve cord may represent a specialized neuromechanosensory structure, appear to have contact chemoreceptive abilities.

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