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Ultrastructural and immunocytochemical investigation of acoel sperms with 9 + 1 axoneme structure: New sperm characters for unraveling phylogeny in Acoela
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics, Systematic Zoology.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics, Systematic Zoology.
Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Evolution, Genomics and Systematics, Systematic Zoology.
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2007 (English)In: Zoomorphology, ISSN 0720-213X, E-ISSN 1432-234X, Vol. 126, no 1, 1-16 p.Article in journal (Refereed) Published
Abstract [en]

Acoel sperm characters proved useful in deciphering acoel taxonomy. The phylogenetic value of sperm characters in closely related sub-groups or in a monophyletic taxon has not yet been assessed. We have investigated sperm ultrastructure in seven members of the monophyletic taxon Childia sensu (Tekle et al. J Zool Sys Evol Res 43(1):72-90, 2005) and in their closest relatives, the Mecynostomidae (four taxa). All members of Childia examined show little variation in their sperm ultrastructure. The common characters of Childia taxa are: 9 + 1 axoneme structure, the presence of six distal cytoplasmic microtubules in the absence of axial or cortical ones, long nucleus and extensive nucleus-flagella overlap. We have identified a new set of cytoplasmic microtubules lying in the centriolar end of the sperm cell, distal microtubules. The origin and phylogenetic significance of this character is discussed. The types and arrangement of cytoplasmic granules could be used as phylogenetic characters at a low taxonomic level. A loose membrane amorphous core type of granule was found to be a synapomorphy for the following clade within the taxon Childia: C. crassum + C. groenlandica + C. vivipara + C. brachyposthium + C. macroposthium. Sausage shaped granules are plesiomorphic among the taxa examined. The rest of the granule characters were found to be homoplasious. Sperm ultrastructural characters have again proven their concordance with molecular phylogeny. The only morphological synapomorphies known for the sister taxa Childia-Mecynostomidae, in the molecular phylogeny, are characters derived from sperm ultrastructure: distal microtubules arranged in two groups of three microtubules each and a 9 + 1 axoneme structure. The spermatozoa of Childia and Mecynostomidae show 9 + 1 axoneme configuration, seemingly similar to the 9 + `1' axoneme pattern of the Platyhelminthes—Trepaxonemata. Using electron-microscope immunocytochemistry, we have demonstrated that, unlike the central cylinder of trepaxonematans, the central cylinder of the 9 + 1 axonemal pattern in acoels is immunoreactive to tubulin and contains a single central microtubule. Therefore, the 9 + 1 patterns in acoels and trepaxonematans are homoplasious.

Place, publisher, year, edition, pages
2007. Vol. 126, no 1, 1-16 p.
Keyword [en]
Acoela, Ultrastructure, Immunocytochemistry, Cytoplasmic microtubules, Flagella
National Category
Biological Sciences
Identifiers
URN: urn:nbn:se:uu:diva-17554DOI: 10.1007/s00435-006-0023-zISI: 000246258000001OAI: oai:DiVA.org:uu-17554DiVA: diva2:45325
Available from: 2008-07-09 Created: 2008-07-09 Last updated: 2017-12-08Bibliographically approved
In thesis
1. Phylogeny and Taxonomy of Childia (Acoela): New characters for unraveling acoel phylogenies from molecules, ultrastructure, immunocytochemistry and confocal microscopy
Open this publication in new window or tab >>Phylogeny and Taxonomy of Childia (Acoela): New characters for unraveling acoel phylogenies from molecules, ultrastructure, immunocytochemistry and confocal microscopy
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis presents a comprehensive phylogenetic and taxonomic study of an acoel subgroup, the Childiidae. Members of this taxon are characterized by well-developed male copulatory organs with conical/cylindrical stylets. The phylogenetic analyses, by means of total evidence approach, based on three molecular markers (18S and 28S rRNA genes and Histone H3) and 50 morphological characters reaffirm the non-monophyly of the Childiidae sensu Dörjes, 1968 (Actinoposthiidae and Childia+Paraphanostoma). The total evidence phylogeny strongly support the Childia+Paraphanostoma clade separate from other former members of the Childiidae, which are now placed in Actinoposthiidae. The monophyly of Childia+Paraphanostoma is well corroborated by several morphological characters. A new taxon Childia is defined, in accordance with the PhyloCode, comprising all former Paraphanostoma species and a member of the monotypic genus C. groenlandica. A new diagnosis for the current members of Childia is provided.

Several structures, shown to hold promising phylogenetic signals for unraveling acoel relationships, such as musculature pattern, sperm and male copulatory organs, are investigated, using a combination of traditional and modern techniques (ultrastructure, immunocytochemistry and confocal microscopy), with main focus on Childia and its closest relatives. New characters are described and their phylogenetic significance assessed. Morphological characters relating to body-wall musculature, statocyst muscles, male copulatory organ musculature and ultrastructure, and sperm cytoplasmic granules are shown to carry important phylogenetic signals at lower taxonomic levels, while most of the characters related to sperm ultrastructure are useful at higher taxonomic levels within the Acoela. The data obtained undermine the phylogenetic use of the seminal bursa in Childia. In addition to this, it is shown that most of the classical morphological characters used in acoel taxonomy, obtained using traditional histological methods, may be misleading in identifying monophyletic entities within the Acoela.

The most corroborated synapomorphies, identified in this thesis, are used in determining the taxonomic placement of a new viviparous acoel, Childia vivipara, into the taxon Childia.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2006. 44 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 140
Keyword
Biology, Childiidae, Childia, Paraphanostoma, Acoela, phylogeny, taxonomy, morphology, 18S rRNA, 28S rRNA, Histone H3, ultrastructure, confocal, phalloidin, immunocytochemistry, Biologi
National Category
Biological Sciences
Identifiers
urn:nbn:se:uu:diva-6315 (URN)91-554-6448-3 (ISBN)
Public defence
2006-02-24, Zootissalen, EBC, Villavägen 9, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2006-01-26 Created: 2006-01-26 Last updated: 2013-06-13Bibliographically approved

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