Mesostoma

Mesostoma is a genus of small, free-swimming flatworms belonging to the order Rhabdocoela. These aquatic invertebrates are commonly found in freshwater environments such as ponds, lakes, and slow-moving streams. Mesostoma are characterized by their elongated, unsegmented bodies, which are typically only a few millimeters in length. They possess a pair of eyespots at the anterior end, which are simple photoreceptors used to detect light. Their ventral surface features a muscular pharynx that can be extended to ingest food.

The diet of Mesostoma primarily consists of small invertebrates, including crustaceans, rotifers, and other micro-organisms. They are predators and actively hunt their prey. Reproduction in Mesostoma can occur both sexually and asexually. Asexual reproduction is often achieved through fragmentation, where the worm divides into two or more pieces, each capable of developing into a complete individual. Sexual reproduction involves the exchange of sperm between individuals, followed by the laying of fertilized eggs. The eggs are typically deposited on submerged vegetation. Mesostoma play a role in aquatic ecosystems as both predators and prey for larger invertebrates and small fish. Their presence can be an indicator of good water quality in freshwater habitats.