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Ultrastructural investigation of coelomocytes in representatives of Naidinae and Rhyacodrilinae (Annelida, Clitellata, Tubificidae)
Stockholm University, Faculty of Science, Department of Zoology.
Zoologiska institutionen, Göteborgs universitet.
Avdelningen för evertebratzoologi, Naturhistoriska riksmuseet.
2008 (English)In: Journal of Morphology, Vol. 269, no 9, 1157-1167 p.Article in journal (Refereed) Published
Abstract [en]

Various types of free-floating cells are found in the coelomic fluid of representatives of several annelid groups. The ultrastructure of these "coelomocytes," however, has been studied to a limited degree. In this study, we used a transmission electron microscope to investigate the coelomocytes in specimens of five species of Naidinae and three species of Rhyacodrilinae (all oligochaetous clitellates within the family Tubificidae). These were compared with each other and with previously described coelomocytes of representatives of other oligochaete taxa. Only one distinguishable coelomocyte type was found in the studied specimens: a round to oblong cell without pseudopodia or other appendages, primarily containing membrane-bound granules of varying electron density, a prominent network of rough endoplasmic reticulum, and free ribosomes. This type differs to a great extent from most of the previously described coelomocytes, but shows similarities to certain types found in members of Enchytraeidae and Megascolecidae. Although we noticed some variation, we did not find any ultrastructural characters in these cells obviously useful for phylogenetic studies within Tubificidae.

Place, publisher, year, edition, pages
2008. Vol. 269, no 9, 1157-1167 p.
National Category
Biological Sciences Zoology Biological Systematics
URN: urn:nbn:se:su:diva-15400DOI: 10.1002/jmor.10652ISI: 000258891600008OAI: diva2:181920
Available from: 2008-12-02 Created: 2008-12-02 Last updated: 2010-10-27Bibliographically approved
In thesis
1. Evolutionary Perspectives on Naidinae (Annelida, Clitellata, Naididae): Molecular and Morphological Revelations
Open this publication in new window or tab >>Evolutionary Perspectives on Naidinae (Annelida, Clitellata, Naididae): Molecular and Morphological Revelations
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Naidinae is a group of tiny oligochaetous clitellates, common all over the world, primarily in freshwater. The taxon includes about 180 nominal species. In this thesis it is shown (using molecular data) that Naidinae (sensu Erséus and Gustavsson, 2002) is non-monophyletic, since one genus, Pristina, formerly regarded as part of Naidinae, is well-separated from the remaining naidines by some genera of another clitellate subfamily, Rhyacodrilinae. The ultrastructure of coelomocytes from several naidine and rhyacodriline species are described and compared with each other and with coelomocytes previously studied, from other clitellate taxa. The naidine and rhyacodriline coelomocytes are similar, differing from those of other groups, which corroborates the hypothesis of a close relationship between Rhyacodrilinae and Naidinae.

Features of the chaetae are important taxonomic characters of Naidinae. However, the significance of chaetotaxy has been questioned. The correlation between genetic variation and chaetal morphology within the genus Nais is investigated. Principally, chaetal character patterns are congruent with the evolutionary lineages revealed by genetic data, but at least nine lineages correspond to at most six nominal species. The species complex Nais communis/variabilis appears to be a gathering of at least five separately evolving lineages. That is, cryptic speciation is revealed.

Finally, six molecular markers are used to elucidate the phylogenetic relationships within the group, and the resulting tree is used to track the evolution of morphological characters commonly used in naidine taxonomy. The tropical genera Dero, Branchiodrilus, and Allonais branch off from the base of the naidine tree of life, suggesting that Naidinae originally evolved in the tropics. Chaetal characters are shown to be homoplastic to a great extent within the group, most certainly contributing to the overall confusion in naidine systematics.

Place, publisher, year, edition, pages
Stockholm: Department of Zoology, Stockholm University, 2009. 48 p.
Naididae, Naidinae, phylogenetics, molecular systematics, morphology, ultrastructure
National Category
Biological Sciences
Research subject
Systematic Zoology
urn:nbn:se:su:diva-27533 (URN)978-91-7155-855-8 (ISBN)
Public defence
2009-06-03, Lilla hörsalen, Naturhistoriska riksmuseet, Frescativägen 40, Stockholm, 13:00 (Swedish)
Available from: 2009-05-13 Created: 2009-05-06 Last updated: 2009-06-01Bibliographically approved

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