Ultrastructural Changes in Earthworm (Eisenia fetida) Nephridia Resulting from Symbiotic Association with Bacteria (Acidovorax sp.)




Jaffarzad, Nina

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This study examined the specific association between earthworms, Eisenia fetida, and the host-specific bacteria in their nephridia, or excretory organs, in order to determine if bacterial colonization of the nephridia resulted in morphological changes in the eukaryotic nephridial cells in contact with the prokaryotic symbionts. It was hypothesized that the bacteria, Acidovorax sp., may induce ultrastructural changes in the nephridia of Eisenia fetida, as has been discovered in other host-microbial systems. The nephridial tissue architecture of symbiont-containing worms was compared with that of worms that developed from eggs treated with antibiotics (asymbionts) by transmission electron microscopy. Presence or absence of bacteria was confirmed by fluorescence in situ hybridization. Results suggest the presence of Acidovorax is necessary for normal development of nephridial structures, in particular microvilli and/or stereocilia on the luminal surface of nephridial epithelial cells.



earthworms, excretory organs, pathogenic bacteria, bacteria


Jaffarzad, N. (2004). Ultrastructural changes in earthworm (Eisenia fetida) nephridia resulting from symbiotic association with bacteria (Acidovorax sp.) (Unpublished thesis). Texas State University-San Marcos, San Marcos, Texas.


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