RADULAR TEETH OF INDO-PACIFIC MOLLUSCIVOROUS SPECIES OF CONUS: A COMPARATIVE ANALYSIS

Abstract

Species determination in the gastropod genus Conus, heretofore exclusively based on shell morphology and color pattern, has led to considerable uncertainty and disagreement. We propose that qualitative and quantitative radular tooth characters are potentially useful in differentiating species as well as geographic subspecies and will improve the taxonomic base. Molluscivorous species of Conus, sometimes placed in the subgenera Cylinder, Textilia, Darioconus, and the nominal subgenus, are taxonomically among the most difficult. We thus examined intra- and interspecific variation in radular morphology of 11 of these species, C. ammiralis, C. araneosus, C. bandanus, C. canonicus, C. episcopatus, C. marmoreus, C. nodulosus, C. omaria, C. pennaceus, C. textile, and C. victoriae, and intra- and interregional variations in radular morphology of C. pennaceus from three geographic regions. Taxonomically useful qualitative characters include presence/absence of one or two barbs and a blade, and whether the row of denticles comprising the serration is continuous or interrupted. Useful metric characters include the ratios of first barb, second barb, blade, serration, shaft width and base width to tooth length, the ratio of tooth length to shell length, the ratio of shaft width to base width, and the degree of curvature of the teeth. Univariate analysis of variance (ANOVA and unplanned pairwise comparison tests) distinguished 53 of the 55 possible species pairs from each other by at least one character. Multivariate analysis of variance (MANOVA) indicated statistically significant differences between the species in the other two pairs. In C. pennaceus, ANOVA and unplanned pairwise tests differentiated Hawaiian from Indian Ocean samples, and MANOVA differentiated those from Maldives and Sumatra. The discrete radular characters sort the 11 species into three groups, and these are consistent with the distribution patterns of the quantitative characters. Radular tooth characters are thus potentially useful in differentiating species and subspecies and should be combined with other character sets in generating future phylogenetic hypotheses.