KinoRoot · Digging out Kinorhynch Roots
Horizon 2020 — Marie Skłodowska-Curie Actions
- Duration
- 2019-03-15 → 2021-03-14
- EU contribution
- €200,195
- Participants
- 1
- Scheme
- MSCA-IF-EF-RI
Lines connect the coordinator with its partners.
Results in brief
Digging out Kinorhynch Roots
Segmentation, i.e., a general body plan composed of repetitive units, has always played a central role in our understanding of animal evolution and phylogeny. The importance of segmentation is expressed in vertebrates and two of the most successful and diverse invertebrate groups, annelids and arthropods, which both follow a strictly segmented body plan. However, researchers tend to neglect the existence of a third highly segmented invertebrate group, the Kinorhyncha or mud dragons. This small phylum contains about 300 described species, all less than 1 mm in length that inhabit marine sediments all around the world. Most of them are characterized by a clearly segmented trunk, which in adults is always composed of eleven segments. The kinorhynchs are related to the unsegmented groups Priapulida (penis worms) and Loricifera (girdle wearers), and together with these were recently suggested to constitute the sister clade to all other Ecdysozoans (molting animals) including the two extremely species-rich phyla Nematoda and Arthropoda. With Kinorhyncha and Arthropoda nested in different subgroups of Ecdysozoa and both presenting a segmented body plan, the key question arises: did segmentation arise before or after the diversification of Ecdysozoa? Two alternative hypotheses will be addressed in order to answer this question: a) Segmentation in kinorhynchs and arthropods is homologous and represents the ancestral ecdysozoan condition, to be found in the ecdysozoan ancestor. b) Segmentation in kinorhynchs and arthropods evolved independently within Ecdysozoa, leaving the Kinorhyncha as a third example of convergently evolved invertebrate segmentation. This would support paleontological findings, suggesting that the ecdysozoan ancestor was an unsegmented worm with a head resembling the kinorhynch head. In both cases, the kinorhynchs represent the essential key to understand the early ecdysozoan evolution. Main objectives: - Examine traces of segmentation in three potentially early branching and unsegmented kinorhynch genera by the use of immunohistochemical staining, confocal laser scanning microscopy (CLSM), histology, and computational 3D reconstruction of muscular and nervous systems. - Analyze phylogenetic relationships among a representative sample of kinorhynch genera, using Illumina RNAseq, in order to determine the positions of the less segmented kinorhynchs one or several of which may constitute the sister group to all remaining Kinorhyncha. - Use the combined results of morphological examinations and phylogenetic analyses to reconstruct the ancestry of segmentation in Kinorhyncha and its evolution within Ecdysozoa. Conclusions: - The muscular and nervous system in “less segmented” kinorhynchs clearly follows a segmental pattern with some modifications. - Morphological and molecular data demonstrate that segmentation is an ancestral trait for kinorhynchs and the “less segmented” or aberrant forms are convergent. - Segmentation most likely evolved independently in kinorhynchs and arthropods.
Data: CORDIS, © European Union
Project objective
The Ecdysozoa includes animals with a hard cuticle. Besides the specious Arthropoda and Nematoda, it also nests minor groups like the Kinorhyncha and Priapulida. The Ecdysozoa accommodates more species than all other organism groups in total. Segmentation occurs in two ecdysozoan clades, Kinorhyncha and Arthropoda, and the project addresses the question whether ecdysozoans evolved from a segmented ancestor or if segmentation evolved twice within Ecdysozoa. Understanding ecdysozoan evolution, is understanding the early evolution of a majority of all living organisms. Through immunohistological morphological examinations of muscular and nervous systems in selected kinorhynchs, and Illumina RNAseq-based phylogenetic analyses, I wish to explore if segmentation, as broadly accepted, is a basal trait for all kinorhynchs. The results will allow us to infer if the ancestral kinorhynch was an unsegmented worm. This work has not previously been achievable due to the lack of a reliable kinorhynch phylogeny, and because the hard kinorhynch cuticle has hampered staining of muscular and nervous systems. However, after next generation sequencing techniques have enabled transcriptomic sequencing from even tiny animals, we are now able to produce an improved kinorhynch phylogeny. Furthermore, I have developed methods to overcome cuticular penetration problems, which makes me one of the very few researchers that can successfully carry out immunohistological studies on kinorhynchs. The project “KinoRoot” unites morphological studies with modern molecular sequencing methods, and builds a bridge between these two scientific fields. The expected outcome will not only apply to people with an interest in kinorhynch evolution. It will be relevant for conceptual morphologists working with segmentation across the animal kingdom, paleontologists working with early Cambrian evolution and in general everyone who has an interest in the early evolution of the large animal groups.
Original text from CORDIS.
Participants
- KOBENHAVNS UNIVERSITET · KOBENHAVNCoordinatorDenmark
Links
Data: CORDIS, © European Union