Septa and nephridia of maldanid polychaetes of the subfamily Maldaninae

Maldaninae thoracic septa and nephridia were described based on dissections of Asychis amphiglyptus, Bathyasychis cristatus, Chirimia lobata, Maldane sarsi, Metasychis disparidentatus, Sabaco elongatus, and Sonatsa meridional is. Maldanins have five anterior septa with the fifth being most developed. The first four thoracic segments are biannulate consisting of an anterior asetous annulus and a posterior setous annulus. The septal boundary of the fifth thoracic segment is shifted posterior such that all or part of the as etous annulus of the sixth thoracic segment functions within the fifth segm ent. The location of the fifth septum, appearance and muscular development of the septa, and anchoring of the gut in the thoracic segments varies amon g the examined specimens. Maldanins have three pairs of metanephridia with nephridiopores that open on the ventrum of setigers seven through nine. Sev eral features of the nephridia vary among the examined species, including s hape, size, exterior development of blood capillaries, and degree by which the longitudinal muscle of the body wall covers the posterior end of the ne phridioduct.