Vegetative cells of the "reinhardtii" species are haploid with 17 small chromosomes. Under nitrogen starvation, vegetative cells differentiate into haploid gametes. There are two mating types, identical in appearance, thus isogamous, and known as mt(+) and mt(-), which can fuse to form a diploid zygote. The zygote is not flagellated, and it serves as a dormant form of the species in the soil. In the light, the zygote undergoes meiosis and releases four flagellated haploid cells that resume the vegetative lifecycle.