page_title: Lake Baikal
section_title: Aquatic worms
hierarchical_section_title: Lake Baikal / Fauna and flora / Invertebrates / Aquatic worms
caption_attribution_description: Русский: Любомирския байкальская (Lubomirskia baicalensis)
context_page_description: Lake Baikal is a rift lake located in southern Siberia, Russia, between Irkutsk Oblast to the northwest and the Buryat Republic to the southeast.
  Lake Baikal is the largest freshwater lake by volume in the world, containing 22–23% of the world's fresh surface water. With 23,615.39 km³ of fresh water, it contains more water than the North American Great Lakes combined. With a maximum depth of 1,642 m, Baikal is the world's deepest lake. It is considered among the world's clearest lakes and is considered the world's oldest lake, at 25–30 million years. It is the seventh-largest lake in the world by surface area.
  Like Lake Tanganyika, Lake Baikal was formed as an ancient rift valley and has the typical long, crescent shape, with a surface area of 31,722 km². Baikal is home to thousands of species of plants and animals, many of which are endemic to the region. It is also home to Buryat tribes, residing on the eastern side of the lake, raising goats, camels, cattle, sheep, and horses, where the mean temperature varies from a winter minimum of −19 °C to a summer maximum of 14 °C.
context_section_description: With almost 200 described species, including more than 160 endemics, the center of diversity for aquatic freshwater oligochaetes is Lake Baikal. A smaller number of other freshwater annelids is known: 30 species of leeches (Hirudinea), and 4 polychaetes. Several hundred species of nematodes are known from the lake, but a large percentage of these are undescribed.
  More than 140 endemic flatworm (Plathelminthes) species are in Lake Baikal, where they occur on a wide range of bottom types. Most of the flatworms are predatory, and some are relatively brightly marked. They are often abundant in shallow waters, where they are typically less than 2 cm (1 in) long, but in deeper parts of the lake, the largest, Baikaloplana valida, can reach up to 30 cm (1 ft) when outstretched.
caption: Museum specimen of the branching sponge Lubomirskia baicalensis (living are brighter green)
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