![]() However, the regulatory mechanism of muscle contraction in tardigrades is unknown. These muscle fibers contain thin and thick filaments in a non-striated pattern. Tardigrades, also known as water bears, have somatic muscle fibers that are responsible for movement of their body and legs. We therefore conclude that the tardigrade brain consists of a singleĭetection of a troponin I-like protein in non-striated muscle of the tardigrades ( water bears) Its association with the second leg- bearing segment in tardigrades suggests that the second trunk ganglion is a homologue of the arthropod tritocerebrum, whereas the first ganglion corresponds to the deutocerebrum. A comparison of the nervous system innervating the foregut and midgut structures in tardigrades and onychophorans to that of arthropods indicates that the stomatogastric ganglion is a potential synapomorphy of Tardigrada and Arthropoda. Furthermore, our results show that the onychophoran pharynx is innervated by a medullary loop nerve accompanied by monopolar, serotonin-like immunoreactive cell bodies. rowelli possesses no immunoreactive neurons, whereas scattered bipolar, serotonin-like immunoreactive cell bodies are found in the midgut wall. In contrast, the oesophagus of the onychophoran E. harmsworthi, which innervates the ectodermal oesophagus and the endodermal midgut and is associated with the second leg- bearing segment. Our data further reveal a hitherto unknown, unpaired stomatogastric ganglion in Macrobiotus cf. A suboesophageal ganglion is clearly lacking. Our immunolabelling against serotonin, FMRFamide and α-tubulin reveals that the tardigrade brain is a dorsal, bilaterally symmetric structure that resembles the brain of onychophorans and arthropods rather than a circumoesophageal ring typical of cycloneuralians (nematodes and allies). harmsworthi and the onychophoran Euperipatoides rowelli. To clarify this, we applied a variety of histochemical and immunocytochemical markers to specimens of the tardigrade Macrobiotus cf. In particular, it is unclear whether the tardigrade head and its enclosed brain comprises one, or several segments, or a non-segmental structure. While recent neuroanatomical and gene expression studies have clarified the alignment of cephalic segments in arthropods and onychophorans, the identity of head segments in tardigrades remains controversial. Mayer, Georg Kauschke, Susann Rüdiger, Jan Stevenson, Paul A Neural markers reveal a one-segmented head in tardigrades ( water bears). Conclusions/Significance A comparison of the nervous system innervating the foregut and midgut structures in tardigrades and onychophorans to that of arthropods indicates that the stomatogastric ganglion is a potential synapomorphy of Tardigrada and Arthropoda. ![]() ![]() Methodology/Principal Findings Our immunolabelling against serotonin, FMRFamide and α-tubulin reveals that the tardigrade brain is a dorsal, bilaterally symmetric structure that resembles the brain of onychophorans and arthropods rather than a circumoesophageal ring typical of cycloneuralians (nematodes and allies). Mayer, Georg Kauschke, Susann Rüdiger, Jan Stevenson, Paul A.īackground While recent neuroanatomical and gene expression studies have clarified the alignment of cephalic segments in arthropods and onychophorans, the identity of head segments in tardigrades remains controversial. ![]() Neural Markers Reveal a One-Segmented Head in Tardigrades ( Water Bears) ![]()
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