planozygote

A planozygote is a type of zygote, the single cell formed by the fusion of two gametes (sex cells) during sexual reproduction, that is not surrounded by a protective shell or wall. This means the embryo develops without any external covering, allowing for direct contact with its environment. This term is primarily used in the study of certain algae, particularly in the context of their life cycles.

In some algal species, such as those in the order Ulotrichales, the planozygote is motile and possesses flagella. These flagella enable it to swim through the aquatic environment. After a period of motility, the planozygote will eventually settle and lose its flagella, becoming a non-motile zygote. This settlement is often a prerequisite for further development and meiosis, which will eventually lead to the formation of new haploid individuals. The naked nature of the planozygote makes it vulnerable to environmental changes and predation.