Intestine ultrastructure of the facultative parasite Halicephalobus gingivalis (Nematoda: Panagrolaimidae)

Abstract

Halicephalobus gingivalis, classified as a free-living nematode, is a known facultative parasite of horses, zebras and humans. However, detailed information concerning its internal morphology is lacking, especially in relation to possible adaptations to its lifestyle as a facultative parasite. The research presented here uses TEM and PI staining to analyse the morphology of the intestine of H. gingivalis. Specimens cultured under different conditions were included to determine if differences in ultrastructure are induced by culturing method. TEM analysis revealed that the intestinal tract comprises a single layer of cells in which nine pairs of nuclei can be distinguished. Further, unusual dichotomously and trichotomously branched microvilli were observed next to finger-like cylindrical microvilli, the latter being the most commonly described form in nematodes. Finally, three different types of secretion vesicles, i.e., spherical (type I), thread-like (type II) and enlarged globular (type III), occurred independently from each other along the intestinal tract. The relationship of morphological adaptations of the microvilli to parasitism in nematodes is discussed

Anthelmintic tolerance in free-living and facultative parasitic isolates ofHalicephalobus(Panagrolaimidae)

“…However, the usefulness of C. elegans as a model for parasitic nematodes has been questioned (Geary and Thompson, 2001), among other reasons simply because it is not capable of parasitism in its natural environment. Halicephalobus gingivalis shares several of the advantages of C. elegans as a model organism: it is amenable to culture under laboratory conditions; it has a very short generation time (2 days at 30°C), produces a lot of offspring, can be cultured in liquid (monoxenic as well as axenic) as well as on solid media (Fonderie et al 2009) and at temperatures ranging from 4°C to more than 40°C ( personal observations, unpublished ). Additionally, H. gingivalis is capable of parasitism in its natural environment.…”

“…They were all light-microscopically identified as the morphospecies Halicephalobus gingivalis using different identification keys (Geraert et al 1988;Shokoohi et al 2007). No males were observed confirming that this species is parthenogenetic (Stefansky, 1954;Andrássy, 1984;Akagami et al 2007;Fonderie et al 2009). The JB128 isolate was obtained from a vegetable compost heap in Riverside (California, USA).…”

“…In addition, 4 cases of human infection, all with a fatal outcome, have been described (Ondrejka et al 2010). H. gingivalis has all the characteristics of a free-living nematode, only at the ultrastructural level can some potential adaptations to facultative parasitism be observed (Fonderie et al 2009). Infection probably occurs through open wounds and oral or nasal cavities (Pearce et al 2001).…”

Reduced Insulin/Insulin-like Growth Factor-1 Signaling and Dietary Restriction Inhibit Translation but Preserve Muscle Mass in Caenorhabditis elegans

“…Three day-2 young adult glp-4 ( bn2 ) daf-16 ( mgDf50 ); daf-2 ( e1370 ) and glp-4 ( bn2 ); daf-2 ( e1370 ) C. elegans nematodes were fixed and transverse sections were prepared according to the procedure described by Fonderie et al ( 83 ). Electron microscopy was done using a Jeol JEM 1010 (Jeol, Tokyo, Japan) operating at 60 kV.…”

Estimation of phylogenetic divergence times in Panagrolaimidae and other nematodes using relaxed molecular clocks calibrated with insect and crustacean fossils

“…The family Panagrolaimidae comprises predominantly free-living nematodes that have evolved to survive in a wide range of substrates and locations. These freeliving bacteriophage nematodes have been associated with soil, leaf-litter, rotting fruit, rotting wood and other fermenting substrates (Lazarova et al, 2004;Barrière & Félix, 2006;Stock & Nadler, 2006;Fonderie et al, 2009;McGill et al, 2015). They have been isolated from diverse habitats such as terrestrial deep subsurface water (Borgonie et al, 2011), deserts (Zhi et al, 2008;Darby et al, 2010) and polar regions (Boström, 1988;Wharton & Brown, 1989).…”