Reproductive system of planarians

The male part of the reproductive system in planarians has a set of several testicles, distributed throughout the body in two or more rows.

Usually associated to the ejaculatory duct, there is a structure formed basically by a fold of the walls of the male atrium called “penis papilla”.

The most common constructions are:[2][3][4] The female part of the reproductive system in planarians is formed by two ovaries in the anterior region.

[5] Among the accessory structures of the reproductive system of planarians, one usually found in freshwater and marine species is the bursa copulatrix, which has the function to store sperm after mating.

[6] Some planarians (such as the genera Planaria, Artioposthia, Arthurdendyus, Coleocephalus and Newzealandia) have a series of finger-like projections, called adenodactyls, near the male and female atria.

Two individuals of Obama ladislavii right after mating. The white structure seen in the upper animal is the protruded penis papilla.
Scheme of the reproductive system of a freshwater planarian
Simplified version of a planarian's reproductive system.
6 different types of penis found in land planarians: (1) permanent penis papilla, protrusible penis; (2) apparent penis papilla; (3) intra-antral penis papilla; (4) inverted penis; (5) absent penis papilla with ejaculatory duct; (6) absent penis papilla without ejaculatory duct.
Reproductive system of Girardia tigrina . The large pouch-like structure on the left is the bursa copulatrix.