The biology and ecology of lotic Tardigrada

• 1 Tardigrades comprise a micrometazoan phylum that is a sister group of the arthropods.
• 2 They are components of the meiobenthos in lotic habitats, and ≈ 50–70 species have been reported in such habitats world‐wide. Approximately 800 species have been identified from all marine, freshwater, and terrestrial habitats.
• 3 Taxonomy is based primarily on the morphology of the claws, buccal‐pharyngeal apparatus, cuticle and eggs.
• 4 Reproductive modes include sexual reproduction (amphimixis) and parthenogenesis. The sexual condition of individuals may be either gonochorism, unisexuality, or hermaphroditism. Moulting occurs throughout the life of the tardigrade.
• 5 Latent states (cryptobiosis, including encystment, anoxybiosis, cryobiosis, osmobiosis and anhydrobiosis) enable tardigrades to withstand unfavourable environmental conditions.
• 6 Population densities, life histories, dissemination and biogeography of freshwater species are poorly known.