Desmid zygote. Differential interference contrast (DIC) light micrograph of a Micrasterias sp. Desmid zygote. Desmids are a common group of freshwater single-celled algae that have intricate cell walls. Desmids can reproduce both asexually and sexually. Sexual reproduction occurs through a process called conjugation where two organisms come together and fuse their haploid cells to form a diploid zygote. This zygote typically forms a thick protective wall that can allow the organism to remain dormant for many months to survive cold winters and long droughts. When adequate conditions resume, the zygospore will germinate, undergo meiosis to produce new haploid algal cells. Magnification: x417 when printed 10 centimetres wide.