Evolution of the nervous system in nematodes - a comparative immunohistochemical approach
Final Report Abstract
It was the aim of the study to compare the structure of the nervous system, especially from the brain, of different nematode taxa to receive a better understanding on the diversity and evolution of nervous system structures within nematodes. Very few such data for a comparative approach were known. Besides a selective interest in economically or medically important nematode species, strongly cuticularized specimens pose strong methodological problems, because of penetration problems for antibodies. In total, 22 species of nematodes from a wide systematic range were collected and processed for nervous system investigation, using a number of different protocols and antibodies against different structures and transmitters of the nervous system (acetylated α-tubulin, tyrosinated α-tubulin, β-tubulin, serotonin, FMRFamides, synapsin, combined with DAPI and phalloidin). The number of investigated specimens was always >100 in cultivated species and between 15 and 100 in free-living species. The exception was only Tobrilus sp., where only 8 specimens could be investigated. Despite numerous variations in the protocols, most of the investigated nematodes did not show any signal. Only from two Plectus species we received good quality signal. The study indicates that several nervous structures can be homologized between C. elegans and Plectus species, but there are also differences, such as the orthogonal pattern of longitudinal neurites and transversal commissures in the trunk region, which is more elaborate in Plectus than in C. elegans. We further included the sister group of Nematoda, Nematomorpha into the project. On the basis of serial histological sections, three-dimensional reconstructions of the anterior end were made. Additionally, single sections were incubated with antibodies against neurogenic substances or structures. Such staining was done the first time successfully in nematomorphs. Our date excellently revealed the presence of a basiepidermal network of neurites and show the three-dimensional structure of the brain. We suggest that the nematomorph brain could be derived from a cycloneuralian brain.
Publications
- (2015): Cycloneuralia (Nematoda, Nematomorpha, Priapulida, Kinorhyncha, Loricifera). In: Structure and Evolution of Invertebrate Nervous Systems. Schmidt-Rhaesa, A., Harzsch, S. & Purschke, G. (eds.). Oxford University Press, Oxford: 368-382
Schmidt-Rhaesa, A. & Henne, S.
