They contain either protonephridia or metanephridia to filter their hemolymph, and are often hermaphroditic.
One subfamily of this phylum is characterized by parapodia reinforced by spiny structures called aciculae, and during reproduction they secrete a viscid sac from the clitellum. Their internal fluids contain a pigment called chlorocruorin, and their larval forms include the metratroch and trochophore. Other sub-taxons include the Myzostomidia which live on crinoids, and the eichuria were recently classified as part of this phylum. Like mollusks, they belong in the lophotrochozoa group, and the largest subgroup of them is the polychaetes. They contain either protonephridia or metanephridia to filter their hemolymph, and are often hermaphroditic. For 10 points, name this protostome phylum consists of the roundworms.
One subfamily of this phylum is characterized by parapodia reinforced by spiny structures called aciculae, and during reproduction they secrete a viscid sac from the clitellum.
{Annelida} or {annelid}s