Comparative myoanatomy of Tardigrada: new insights from the heterotardigrades Actinarctus doryphorus (Tanarctidae) and Echiniscoides sigismundi (Echiniscoididae).

Background: Tardigrada is a group of microscopic invertebrates distributed worldwide in permanent and temporal aquatic habitats. Famous for their extreme stress tolerance, tardigrades are also of interest due to their close relationship with Arthropoda and Cycloneuralia. Despite recent efforts in analyzing the musculature of a number of tardigrade species, data on the class Heterotardigrada remain scarce.

Desiccation tolerance in the tardigrade Richtersius coronifer relies on muscle mediated structural reorganization.

Life unfolds within a framework of constraining abiotic factors, yet some organisms are adapted to handle large fluctuations in physical and chemical parameters. Tardigrades are microscopic ecdysozoans well known for their ability to endure hostile conditions, such as complete desiccation--a phenomenon called anhydrobiosis. During dehydration, anhydrobiotic animals undergo a series of anatomical changes.

Inorganic ion composition in Tardigrada: cryptobionts contain a large fraction of unidentified organic solutes.

Many species of tardigrades are known to tolerate extreme environmental stress, yet detailed knowledge of the mechanisms underlying the remarkable adaptations of tardigrades is still lacking, as are answers to many questions regarding their basic biology. Here, we present data on the inorganic ion composition and total osmotic concentration of five different species of tardigrades (Echiniscus testudo, Milnesium tardigradum, Richtersius coronifer, Macrobiotus cf. hufelandi and Halobiotus crispae) using high-performance liquid chromatography and nanoliter osmometry.

First evidence of epithelial transport in tardigrades: a comparative investigation of organic anion transport.

We investigated transport of the organic anion Chlorophenol Red (CPR) in the tardigrade Halobiotus crispae using a new method for quantifying non-fluorescent dyes. We compared the results acquired from the tardigrade with CPR transport data obtained from Malpighian tubules of the desert locust Schistocerca gregaria. CPR accumulated in the midgut lumen of H.

Cyclomorphosis in Tardigrada: adaptation to environmental constraints.

Tardigrades exhibit a remarkable resilience against environmental extremes. In the present study, we investigate mechanisms of survival and physiological adaptations associated with sub-zero temperatures and severe osmotic stress in two commonly found cyclomorphic stages of the marine eutardigrade Halobiotus crispae. Our results show that only animals in the so-called pseudosimplex 1 stage are freeze tolerant.

Myoanatomy of the marine tardigrade Halobiotus crispae (Eutardigrada: Hypsibiidae).

The muscular architecture of Halobiotus crispae (Eutardigrada: Hypsibiidae) was examined by means of fluorescent-coupled phalloidin in combination with confocal laser scanning microscopy and computer-aided three-dimensional reconstruction, in addition to light microscopy (Nomarski), scanning electron microscopy, and transmission electron microscopy (TEM). The somatic musculature of H. crispae is composed of structurally independent muscle fibers, which can be divided into a dorsal, ventral, dorsoventral, and a lateral musculature.