The biology and ecology of lotic Tardigrada

Abstract

Summary Tardigrades comprise a micrometazoan phylum that is a sister group of the arthropods. 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. Taxonomy is based primarily on the morphology of the claws, buccal‐pharyngeal apparatus, cuticle and eggs. 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. Latent states (cryptobiosis, including encystment, anoxybiosis, cryobiosis, osmobiosis and anhydrobiosis) enable tardigrades to withstand unfavourable environmental conditions. Population densities, life histories, dissemination and biogeography of freshwater species are poorly known.

Nearctic freshwater tardigrades: a review

“…Three species -Milnesium tardigradum, Hypsibius convergens, and Macrobiotus hufelandi -are eurytopic species that sometimes inhabit freshwater habitats (Nelson & Marley 2000). The remaining 23 species in table 1 are rarely found in freshwater, and most probably washed into streams or lakes from terrestrial substrates.…”

“…Freshwater tardigrades are benthic animals, crawling on the surface of aquatic plants or algal mats, or in the interstices of sandy sediments (Nelson & Marley 2000). Specimens have been found in plankton samples, but their presence in the water column probably results from benthic disturbance (Van Rompu et al 1992).…”

“…distinctly aquatic, species. Other tardigrades sometimes found in aquatic habitats include the hygrophilous species characteristic of moist mosses and eurytopic species which tolerate a wide range of moisture conditions (Nelson & Marley 2000). This paper reviews the diversity and distribution of freshwater tardigrades in North America, the types of habitats in which they have been found, and their population ecology.…”

Extremophiles and the Search for Extraterrestrial Life

“…They represent a separate phylum that is related to arthropods (Nelson and Marley, 2000). More than 800 species have been described from marine, freshwater, and terrestrial habitats.…”

Diversity and distribution of tardigrades (Bilateria, Tardigrada) from the Iberian Peninsula, Balearic Islands and Chafarinas Islands

“…Tardigrades are micrometazoans that can be found world-wide (McInnes, 1994;Nelson & Marley, 2000), in many types of habitats (aquatic and terrestrial) within a film of water (Ramazzotti & Maucci, 1983;Nelson, 1995). They are specially interesting for their capacity to enter in criptobiosis (Crowe, 1975;Nelson, 1995), with posible future applications in biomedicine (Crowe & Crowe, 2000).…”