Melosira nummuloides with auxospore
Most diatoms reproduce asexually, which tends to result in progressively smaller sizes. When reduction in size is severe or environmental conditions necessitate it, sexual reproduction occurs with the production of auxospores. These larger cells act to reestablish larger size diatoms. This sample came from the Rhode River in July of 2002. The environment was suffering from a long drought, which increased the salinity to higher than normal levels. The water temperature was also elevated due to the extremely high air temperatures. Whether or not these conditions stimulated the formation of auxospores on Melosira is not confirmed.