Acrosomata

from Wikipedia, the free encyclopedia

The division of living beings into systematics is a continuous subject of research. Different systematic classifications exist side by side and one after the other. The taxon treated here has become obsolete due to new research or is not part of the group systematics presented in the German-language Wikipedia.

The Acrosomata are a hypothetical taxon of the phylogenetic system , which combines the rib jellyfish (Ctenophora) with the bilaterally symmetrical animals ( Bilateria ). Thus they represent one of the alternatives to the hollow animals (Coelenterata) of the classical system, in which the comb jellyfish are combined with the cnidarians (Cnidaria).

The monophyly of the Acrosomata is justified by two central morphological characteristics. The eponymous feature is the structure of the sperm , which have a so-called acrosome and an underlying subacrosomal substance (perforatorium). This structure of the sperm can be demonstrated in all animal groups of the Bilateria as well as in the comb jellyfish. The second correspondence lies in the structure of the muscle cells , which, in contrast to the cnidarians, are not developed as epithelium and can be viewed as independent myocytes .

The Acrosomata hypothesis is now considered more of an outsider hypothesis within science. In fact, for various reasons it does not seem implausible today that such features could have developed convergently to one another several times . Acrosomes have also been detected in sperm from sponges, and there are good arguments that the muscle cells of the comb jellyfish have developed convergent to those of the bilateria . Since the actual position of the comb jellyfish in the natural system of multicellular animals, as well as the entire phylogeny of the five basal groups Ctenophora, Porifera, Placozoa, Cnidaria, Bilateria, contrary to earlier optimistic assumptions, has not yet been clarified, it has not yet been definitively refuted. Two hypotheses in particular are examined as alternatives:

Coelenterata

New arguments have recently been put forward for the classic taxon of the coelenterate or coelenterata, i.e. a sister group relationship between the rib jellyfish and the cnidarians or cnidaria. This includes, in addition to phylogenomic results. for example the pattern of furrows in early embryonic development

Ctenophora as the most basal branch

The hypothesis made in 2008 on the basis of a phylogenomic analysis that the comb jellyfish could be the most basic branch of the higher animals, i.e. the sister group of all other Metazoa taken together, has attracted a great deal of scientific attention due to the far-reaching conclusions they would allow. However, the basic work was soon accused of methodological deficiencies. But further genetic data as well as arguments about the development of the nervous system support the hypothesis.

Individual evidence

  1. ^ Peter Ax: Multicellular Animals: A new Approach to the Phylogenetic Order in Nature. Volume 1. Springer, Berlin / Heidelberg, 2012. ISBN 978-3-642-80114-3 . Acrosomata on page 104.
  2. ↑ Casey W. Dunn, Sally P. Leys, Steven HD Haddock (2015): The hidden biology of sponges and ctenophores. Trends in Ecology & Evolution 30 (5): 282-291. doi: 10.1016 / j.tree.2015.03.003
  3. ↑ Martin Dohrmann & Gert Wörheide (2013): Novel Scenarios of Early Animal Evolution — Is It Time to Rewrite Textbooks? Integrative and Comparative Biology 53 (3): 503-511. doi: 10.1093 / icb / ict008
  4. ↑ Bernd Schierwater, Peter WHHolland, David J. Miller, Peter F. Stadler, Brian M. Wiegmann, Gert Wörheide, Gregory A. Wray, Rob DeSalle (2016): Never Ending Analysis of a Century Old Evolutionary Debate: “Unringing” the Urmetazoon Bell. Frontiers in Ecology and Evolution 4 (5): 1-13. doi: 10.3389 / fevo.2016.00005
  5. ↑ H. Philippe, R. Derelle, P. Lopez, K. Pick, C. Borchiellini, N. Boury-Esnault, J. Vacelet, E. Renard, E. Houliston, E. Quéinnec, C. Da Silva, P. Wincker, H. Le Guyader, S. Leys, DJ Jackson, F. Schreiber, D. Erpenbeck, G. Morgenstern, G. Wörheide, M. Manuel (2009): Phylogenomics Revives Traditional Views on Deep Animal Relationships. Current Biology 19 (8): 706-712. doi: 10.1016 / j.cub.2009.02.052
  6. ↑ Gerhard Scholtz (2004): Coelenterata versus Acrosomata - on the position of the rib jellyfish (Ctenophora) in the phylogenetic system of the Metazoa. In S. Richter, S. & W. Sudhaus (editor): Controversies in the Phylogenetic Systematics. Meeting reports of the Society of Friends of Natural Sciences in Berlin (NF) 43: 15-33.
  7. ↑ CW Dunn, A. Hejnol, DQ Matus, K. Pang, WE Browne, SA Smith, E. Seaver, GW Rouse, M. Obst, GD Edgecombe, MV Sørensen, SHD Haddock, A. Schmidt-Rhaesa, A. Okusu , R. Møbjerg Kristensen, WC Wheeler, MQ Martindale, G. Giribet (2008): Broad phylogenomic sampling improves resolution of the animal tree of life. Nature. 452: 745-749.
  8. ↑ Leonid L. Moroz, Kevin M. Kocot, Mathew R. Citarella, son Dosung, Tigran P. Norekian, Inna S. Povolotskaya, Anastasia P. Grigorenko, Christopher Dailey, Eugene Berezikov, Katherine M. Buckley, Andrey Ptytsyn, Denis Reshetov , Krishanu Mukherjee, Tatiana P. Moroz, Yelena Bobkova, Fahong Yu, Vladimir V. Kapitonov, Jerzy Jurka, Yuri Bobkov, Joshua J. Swore, David O. Girardo, Alexander Fodor, Fedor Gusev, Rachel Sanford, Rebecca Bruders, Ellen Kittler , Claudia E. Mills, Jonathan P. Rast, Romain Derelle, Victor V. Solovyev, Fyodor A. Kondrashov, Billie J. Swalla, Jonathan V. Sweedler, Evgeny I. Rogaev, Kenneth M. Halanych, Andrea B. Kohn (2014 ): The Ctenophore Genome and the Evolutionary Origins of Neural Systems. Nature 510 (7503): 109-114. doi: 10.1038 / nature13400