A Fifth Morphological Polyp in Pennatulacean Octocorals, with a Review of Polyp Polymorphism in the Genera Pennatula and Pteroeides (Anthozoa: Pennatulidae)

Four types of polyps that differ in morphology and function were previously described in pennatulacean octocorals: oozooids, autozooids, siphonozooids, and mesozooids. Here we describe a 5th type of polyp, the acrozooid, found in members of 2 species of the genus Pteroeides from tropical western Pacific coral reef regions. The polyps appear in clusters of up to 14 in number on the ventral side and distal terminus of the rachis, and are characteristically urn-shaped, with 8 triangularly shaped tentacles. The polyp walls contain smooth, elongated rod-like sclerites, which are similar to those found in the coenenchyme of parent colonies. We postulate that these polyps represent maturing asexual budding structures.