Life history of the freshwater microturbellarian <i>Macrostomum velastylum</i> (Macrostomorpha) in the Neotropical region

The genus Macrostomum (Platyhelminthes: Macrostomorpha) is a group of cosmopolitan free-living flatworms that occurs in a wide range of habitats. In our study, individuals of Macrostomum velastylum were collected from the Sagastume stream (33°38ʹ34ʺS; 58°49ʹ63ʺW) Entre Ríos Province, Argentina, during 2016. They were kept in laboratory at room temperature in order to study population parameters (1, fecundity; 2, hatching rate and hatching time; 3, male sexual maturation time; and 4, longevity). The results show that this species laid 1.5 eggs per day per individual, the hatching rate was 85% and most eggs hatched between the first and second week after laying. The maturation time showed an extensive range of time to reach sexual maturation. The average longevity was 96 ± 33 days. Considering the laboratory conditions and the scarce information on life cycles on Macrostomum species, these results are promising for future interspecific comparative studies.