Stilbonematinae is a subfamily of the nematode worm family Desmodoridae that is notable for its symbiosis with sulfur-oxidizing bacteria.
| Stilbonematinae | |
|---|---|
Scientific classification 
| |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Nematoda |
| Class: | Chromadorea |
| Order: | Desmodorida |
| Family: | Desmodoridae |
| Subfamily: | Stilbonematinae Chitwood, 1936 |
| Genera | |
|
(See article text) | |
Systematics
editStilbonematinae Chitwood, 1936 belongs to the family Desmodoridae in the order Desmodorida. Nine genera have been described.[1]
- Adelphos Ott, 1997
- Catanema Cobb, 1920
- Centonema Leduc, 2013
- Eubostrichus Greeff, 1869
- Laxus Cobb, 1894
- Leptonemella Cobb, 1920
- Parabostrichus Tchesunov et al. 2012
- Robbea Gerlach, 1956
- Squanema Gerlach, 1963
- Stilbonema Cobb, 1920
Description
editStilbonematines can be up to 10 mm long, with a club-like head. The worms are completely covered in a coat of ectosymbiotic sulfur-oxidizing bacteria except for the anterior region. The presence of the bacteria, which often contain intracellular inclusions of elemental sulfur, gives the worms a bright white appearance under incident light. They have small mouths and buccal cavities, and short pharynges. Many species have multicellular sensory-glandular organs in longitudinal rows along the length of the body, which secrete mucus that the bacterial symbionts are embedded in.[1]
Stilbonematines are found in the meiofaunal habitat in marine environments.[2] Another group of meiofaunal nematodes with sulfur-oxidizing symbionts is the genus Astomonema, although in Astomonema the bacteria are endo- rather than ectosymbionts.
Symbiosis with sulfur-oxidizing bacteria
editThe bacterial symbionts of stilbonematines are of different shapes and sizes, ranging from small coccoid cells to elongate crescent-like cells, but each host species has only a single morphological type associated with it.[3] The bacterial symbionts of stilbonematines are closely related to the sulfur-oxidizing symbionts of gutless phallodriline oligochaete worms: these bacteria were all descended from a single ancestor, and each host species has its own specific bacterial species.[4]
The bacterial symbionts are chemosynthetic, gaining energy by oxidizing sulfide from the environment, and producing biomass by fixing carbon dioxide through the Calvin-Benson-Bassham cycle.[3] The bacteria benefit from the symbiosis because the host animal can migrate between sulfide- and oxygen-rich regions of the sediment habitat, and the bacteria require both these chemical substances to produce energy. The hosts are believed to consume the bacteria as a food source, based on evidence from their stable carbon isotope ratios.[5]
The specificity of the bacterial symbionts to their respective host species is controlled by a lectin called Mermaid that is produced by the worms. Mermaid occurs in different isoforms, which have differing affinities for the sugar compositions of the lipopolysaccharide coat in different bacterial species.[6]
See also
edit- Olavius algarvensis - A species of gutless phallodriline oligochaete worms whose sulfur-oxidizing bacterial symbionts are related to those of the stilbonematine nematodes.
- Astomonema - A genus of nematodes (from a different family) that also has symbiotic sulfur-oxidizing bacteria.
References
edit- ^ a b Tchesunov, Alexei V. (February 2013). "Marine free-living nematodes of the subfamily Stilbonematinae (Nematoda, Desmodoridae): taxonomic review with descriptions of a few species from the Nha Trang Bay, Central Vietnam". Meiofauna Marina. 20: 71–94.
- ^ Ott, Jörg; Bright, Monika; Bulgheresi, Silvia (2004). "Symbioses between marine nematodes and sulfur-oxidizing chemoautotrophic bacteria". Symbiosis. 36: 103–126.
- ^ a b Polz, Martin F.; Felbeck, Horst; Novak, Rudolf; Nebelsick, Monika; Ott, Jörg A. (1992-11-01). "Chemoautotrophic, sulfur-oxidizing symbiotic bacteria on marine nematodes: Morphological and biochemical characterization". Microbial Ecology. 24 (3): 313–329. doi:10.1007/bf00167789. ISSN 0095-3628. PMID 24193210.
- ^ Zimmermann, Judith; Wentrup, Cecilia; Sadowski, Miriam; Blazejak, Anna; Gruber-Vodicka, Harald R.; Kleiner, Manuel; Ott, Jörg A.; Cronholm, Bodil; De Wit, Pierre (2016-07-01). "Closely coupled evolutionary history of ecto- and endosymbionts from two distantly related animal phyla". Molecular Ecology. 25 (13): 3203–3223. doi:10.1111/mec.13554. ISSN 1365-294X. PMID 26826340.
- ^ Ott, J. A.; Novak, R.; Schiemer, F.; .Hentschel, U; Nebelsick, M.; Polz, M. (1991-09-01). "Tackling the Sulfide Gradient: A Novel Strategy Involving Marine Nematodes and Chemoautotrophic Ectosymbionts". Marine Ecology. 12 (3): 261–279. doi:10.1111/j.1439-0485.1991.tb00258.x. ISSN 1439-0485.
- ^ Bulgheresi, Silvia; Gruber-Vodicka, Harald R.; Heindl, Niels R.; Dirks, Ulrich; Kostadinova, Maria; Breiteneder, Heimo; Ott, Joerg A. (June 2011). "Sequence variability of the pattern recognition receptor Mermaid mediates specificity of marine nematode symbioses". The ISME Journal. 5 (6): 986–998. doi:10.1038/ismej.2010.198. ISSN 1751-7362. PMC 3131856. PMID 21228893.