Morphological Development of the Radula of Four Species of the Neogastropod Family Muricidae

Abstract

Radular ontogenies of four species of the neogastropod family Muricidae are describedthrough comparisons of early post-metamorphic and adult developmental stages, with specificfocus on the rachidian (central) tooth. The degree of rachidian transformation during ontogenyvaries from minor shape change to addition or loss of structural features important forassigning taxa to subfamilies. Changes include: flattening of the rachidian base and a switchfrom a short, beak-like to a long, flattened central cusp in the rapanine Stramonita biserialis;a switch from variable, asymmetric to regular, symmetric expression of inner lateral denticlesin the basal muricid Timbellus phyllopterus; curvature of the rachidian base at the marginsand separation of the pointed base endpoint from the radular membrane to form a marginalcusp in the muricine Chicoreus dilectus; and moderate straightening of the rachidian basein the ocenebrine Vokesinotus perrugatus. From these observations and previous work, wepropose a plesiomorphic developmental sequence for the Muricidae and provide supportingevidence for the developmental origins of novel features of the muricid radula.