PROBOSCIDIAL PAPILLAE OF THE GLYCERIDAE (ANNELIDA: POLYCHAETA) AND THEIR VALUE AS A TAXONOMIC CHARACTER
Böggemann, M. & Fiege, D.
1Forschungsinstitut und Naturmuseum Senckenberg, Senckenberganlage 25, D-60325 Frankfurt/M., Germany.
The Glyceridae occur worldwide, mostly on sandy substrates from the intertidal to the deep sea. They are considered carnivorous and capture their prey with four jaws, situated at the end of the eversible proboscis, which is densely covered by papillae. According to our revision of this family based on light and scanning electron microscopy only a quarter of the about 160 taxa described until today represent valid species. Re-evaluation of the main identification characters using SEM showed that the proboscidial papillae provide a suitable character for the distinction even of closely related species. The proboscidial papillae appear in a variety of species-specific types based on their shape, size and the morphology of their aboral sides. Specimens from various locations were often attributed to G. americana Leidy, 1855 mainly because of their bush-like branchiae. However, as branchiae are retractable and therefore often difficult to evaluate we focused on the proboscidial papillae. Our studies show that the taxon G. americana represents a species complex which has to be divided into three separate species bearing proboscidial papillae with either two or three ridges or an Y-shaped ridge in combination with one to three vertical ridges at the tip. All three species are clearly separated by their geographical distribution. A similar situation can be found in G. tesselata Grube, 1863. Specimens were attributed to this species mainly because of the presence of a deeply incised aileron. Based on the shape of the digitiform papillae, however, three species can be distinguished: digitiform papillae either with many ridges or an oval terminal structure or with a straight median ridge. The use of the main types of papillae as an important identification character enables us to divide the genus Glycera into three distinguishable groups: species with 1. "fingernail", 2. digitiform, or 3. conical papillae; each papilla characterized by a certain number and form of ridges or sometimes without any structures.