Nemertoderma

Nemertoderma is a genus of minute, marine turbellarian flatworms belonging to the family Nemertodermatidae. These are small, free-living invertebrates found in marine sediments and shallow waters worldwide. They are characterized by their simple, unsegmented body plan and the absence of a coelom. Their digestive system is typically incomplete, with a pharynx and a blind gut.

Members of Nemertoderma are notable for their unusual reproductive biology. Many species are hermaphroditic, possessing both male and female reproductive organs. Reproduction can occur through self-fertilization or cross-fertilization. Some species are known to reproduce asexually through fragmentation.

The genus was first described in 1904. While their exact phylogenetic position has been debated, they are generally considered to be among the most basal of the Lophotrochozoa, a large phylum of invertebrates. Their small size and cryptic lifestyle can make them difficult to study, and research on their ecology and evolutionary relationships is ongoing. They play a role in benthic ecosystems as consumers of small organic particles and microorganisms.