INTERNAL ANATOMY FEATURES OF MALDANIDAE POLYCHAETES OF THE SUBFAMILY MALDANINAE
Green, K. D.
MEC Analytical Systems, Inc. 2433 Impala Drive, Carlsbad, California, 92008, USA.
Maldaninae septa and nephridia are described based on dissections of Asychis amphiglyptus, Bathyasychis cristatus, Chirimia lobata, Maldane sarsi, Metasychis disparidentatus, Sabaco elongatus, and Sonatsa meridionalis. Maldanins have five anterior septa with the fifth being most developed. The first four septa divide setigers 1 through 4 into biannulate segments consisting of an anterior asetous annulus and a posterior setous annulus. Each annulus has distinct external boundaries, and the first four septa correspond in position internally with the external boundaries immediately posterior to the setous annuli. The fifth setigerous segment is unique in that the septal boundary between the fifth and sixth setiger is shifted posterior such that all or part of the asetous annulus anterior to the sixth seteous annulus functions within the fifth segment. Thus, the fifth segment generally is tripartite with an anterior asetous annulus, setous annulus, and posterior asetous annulus. Consequently, there is a lack of correspondence betweeen the internal septal boundary and the external boundary of the setous annulus on the fifth setiger. The muscular development of the fifth septum is variable among the examined genera . All examined maldanins have three pairs of nephridia with nephridiopores (external openings) on setigers 7 through 9. Each nephridium consists of an anterior nephrostome, main body, and posterior nephridiopore. Each nephrostome is internally located just posterior to the position of the neuropodium of the segment preceding the segment where the nephridiopore is located. Each nephridiopore opens on the ventrum at the base of the neuropodium. The muscular attachment of the nephrostome to the body wall and shape of the nephridia vary among the examined genera. Variations in the appearance of the septa and nephridia in maldanid polychaetes suggest they may be useful taxonomic characters.