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LINUX Cluster Project

LRZ-Dienste - LMU München Paläontologie u. Geobiologie


Institution

  • Name: Department für Geo- und Umweltwiss. Lehrstuhl Paläontologie und Geobiologie
  • Address: Richard-Wagner-Straße 10, 80333 München
  • Project Proposal Date: 2019-10-08 12:02:31

Abstract:

Looking for the origin of giant ostracod spermatozoa Ostracods, bivalved aquatic microcrustacea occur in almost every marine, brackish, and freshwater habitat. Their extant distribution and density, their ecological diversification, and finally their fossil abundance as from Ordovician age (500 My) have made them important research objects in the fields of biology and palaeontology. Spermatozoa of freshwater ostracods are giant spermatozoa. These spiral, filiform cells are only a few microns thick and can reach up to 10 mm length, or, up to ten times the body-length of the male carrying them. Their outer sheaths of so far unknown composition (presumably chitin) are extraordinarily stable, exemplified by findings of sperms attached to 5,000 year-old valves ? the oldest record of spermatozoa not embedded in amber. In order to ensure a successful sperm transfer, the two sperm pumps (known as Zenker organs) push the long sperm cells through the hemipenes into the female vaginas. Such a pump is a voluminous organ consisting of a chitinous ?skeleton? and muscles, and their presence in an ostracod is a clear (indirect) proof of giant sperms. In order to track the evolutionary origin of giant ostracod spermatozoa it is necessary to investigate fossils with preserved soft parts. Such fossils are rare and valuable ? we therefore applied a non-invasive high-resolution method for their investigation: the propagation phase-contrast microtomography, currently only available at the European Synchroton Radiation Facility in Grenoble. Our material comprises three-dimensionally preserved ostracods from the Brazilian Santana Formation (100 mio yrs) ? calcite/apatite fossils with exceptionally well-preserved soft parts, including chaetal micro-structures. As a result of the radiation procedure, approximately 40 sets of TIF images (each with c. 1500 files) can now be used for 3-D reconstruction of the fossils and their Recent reference material. These data amounts are much too voluminous to be handled in the workstations provided by our institute. We therefore apply for assistance by the LRZ in providing a remote access to the RVS1. Deep Metazoan Phylogeny In the framework of several DFG funded research projects on the phylogeny of the Metazoa we request access to parallel computing to carry out phylogenetic and phylogenomic analysis, which are too computationally intensive to carry out on desktop computers. Abstract: Deep level metazoan relationships are still far from being resolved. Expanding molecular datasets and continuing advances in phylogenomic methods are increasingly being used, but important nodes among non-bilaterian animals remain difficult to resolve. For example, some recent phylogenomic analyses found ctenophores to be the earliest-branching metazoan taxon and favoured a sister-group relationship between sponges and cnidarians, while other analyses suggest that the Placozoa diverged first or that sponges are a paraphyletic assemblage that share a grade of construction rather than common ancestry. We have now assembled several multi-gene datasets derived from ESTs, with different taxon- and gene-sampling. A strongly supported monophyletic Porifera with unexpected internal topology is always recovered and most analyses favour a sister-group relationship of Ctenophora+Cnidaria, reviving the "Coelenterata" concept. However, Placozoa relationships remain unstable as they are highly dependent on taxon sampling, evolutionary model selection and outgroup choice. In the last phase of the project we will test these hypotheses by adding additional data of selected taxa and conduct more critical data analyses aiming at a more robust resolution of the branching order of all non-bilaterian metazoan groups.