Rotifer

Rotifers are tiny animals, typically less than 1 mm in length, with most species inhabiting freshwater environments. They may be either sedentary or free-swimming. Their bodies are covered with an epidermis, which can include a rigid layer called a lorica, mainly on the thorax. Rotifers have a unique rotary organ on their head, known as the corona, which gives this group its name. The corona consists of two ciliated spots shaped like rings, known as the trochus. By beating these cilia, rotifers either capture food or propel themselves. They lack developed circulatory and respiratory systems. Rotifers have separate sexes, and females are capable of reproducing without males through a process called parthenogenesis. Males are much smaller than females, lack a digestive system, and have a very short lifespan. Anabiosis is common among soil-dwelling rotifer species. During anabiosis, rotifers desiccate and form a protective mucous capsule, allowing them to survive without water for several years until favorable conditions return.