Dugesia mertoni
Dugesia mertoni was superficially described by Paul Steinmann in 1914 on the basis of not fully mature and not well preserved specimens. These individuals were collected from one of the Kai Islands, Indonesia. In 1990, this species was redescribed in more detail by Ronald Sluys and Ian R. Ball from individuals collected in New Britain, Papua New Guinea.
Externally, it looks like any other Dugesia species; it presents a triangle-shaped head given by the two auricles, two eyes in the middle, and an elongated and flattened body.
Focusing on the morphology of the reproductive apparatus, this species has a common oviduct, a character also present in D. lindbergi, D. andamanensis, D. congolensis, and D. myopa.
Their dorsal surface is brown-yellow while the ventral surface is pale. As other Dugesiid species, the eyes are multicellular cups containing numerous retinal cells.
Preserved specimens up to 10 mm in length and 4 mm in width.
Freshwater planarians depend on contiguous freshwater bodies to disperse. After this species is present in Kai Islands and Papua New Guinea it's not likely that they disperse in recent times, but in a period when sea level was lower and rivers or streams from these islands were in contact.
Kai Islands (Indonesia) and New Britain, Bismarck Archipelago (Papua New Guinea).