Trichosphaerium is a multinucleated marine amoeba known to exhibit different morphotypes. Most eukaryotic amoebas have a defined shape and size at some stages of their life, which is critical for taxonomic and behavioral studies. In some cases, variations in form or size are seen in alternating forms of an organism representing different stages in a life cycle. However, it is unusual to see a behavior involving large variations in size and shape throughout a life cycle as exhibited in Trichosphaerium. The life cycle of Trichosphaerium is poorly documented. In this study cultures of Trichosphaerium were observed for 26 days to gain insights about its life cycle. Study of its growth display an increase in size from Day 1, before reaching a stagnant period to Day 20, and decreasing until Day 26. Live videos of Trichosphaerium showed evidence of fragmentation and cellular fusion. Immunocytochemistry staining of live and fixed amoeba cells revealed evidence of the nuclear fusion, where few nuclei exceeding average nuclear size were observed. Genetic study showed that Trichosphaerium expressed meiosis-specific genes, which support that the cellular and nuclear fusion observed during the development are likely of sexual stages.
