Morphological Variation in Nautilus from Papua New Guinea

Abstract

The generally held consensus has been that Nautilus exhibits little morphological variability (e.g., Ward, 1984). However, it is relevant that most studies of morphological variation have been restricted largely to comparisons of mature shell size and weight and to documentation of sexual dimorphism within individual populations (e.g., Hirano, 1977; Saunders and Spinosa, 1978; Hayasaka et al., 1982, 1983; Tanabe et al., 1983; Ward, 1984; Saunders and Davis, 1985) (see also Chapter 3). The first effort to evaluate “whole animal” variation (Tanabe et al., 1983) involved analysis of nine shell and body characters taken from samples of N. pompilius from the Philippines and from Fiji. Partly because of sample size limitations, the results of that study only tended to confirm earlier observations of sexual dimorphism and of mature size differences between the two populations. Two expanded studies, by Tanabe et al. (1985) and by Tanabe and Tsukahara (Chapter 7), have shown that these two widely separated populations do exhibit a fairly large degree of variation.