Meeting Abstract
The Spatangoida, commonly known as heart urchins, are among the most diverse sea urchin groups. Unlike other urchins, spatangoids have evolved secondary bilateral symmetry, with an anterior-posterior axis allowing them to move in one direction through the sands in which they live. The brissid genus Metalia Gray, 1855 has been characterized by its shield-shaped subanal fasciole, with extensions as anal fascioles on either side of the anal opening. However, morphology is insufficient to demonstrate monophyly of Metalia. Although Metalia includes some of the largest, most common heart urchins in the Indo-Pacific, the systematics are far from settled, with several new species to be described. We present the first partial phylogenetic analysis of the Brissidae using mitochondrial COI and nuclear 28S genes from M. spatagus, M. sternalis, M. nobilis, M. dicrana, and at least one new species (“big red”). Generic monophyly was tested using species of Brissus, Brissalius, Anametalia, Meoma, Plagiobrissus, Eupatagus, Rhynobrissus, and Brissopsis. For the most part, Metalia species grouped together, but there is an intriguing possibility that the aberrant Plagiobrissus is derived from within Metalia, as suggested by ontogenetic studies. The long-recognized species, M. sternalis, actually seems to consist of 2 species: a giant and a small form (the latter once thought to be juveniles of the former). We are working towards increased taxon sampling, and a careful integration of morphological evidence to describe new species, determine biogeographic patterns, and provide a clearer view of the evolutionary pathways that make this genus such an important element in coral reef ecosystems.
