Geomonhystera

 

Contents

 

Rev: 11/19/2024

  Classification Biology and Ecology
Morphology and Anatomy Life Cycle
Return to Geomonhystera Menu Ecosystem Functions and Services
Distribution Management
Return to Monhysteridae Menu Feeding  References
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Classification:

Chromadorea
  Chromadoria
   Monhysterida
Monhysterina
Monhysteroidea
            Monhysteridae
Monhysterinae
       Geomonhystera Andrassy, 1981
    Synonyms:
      
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Morphology and Anatomy:

The genus Geomonhystera was erected by Andrassy (1981) for terrestrial species that have general characters of the Monhysteridae but, among other features, the vulva is located at around 80% of the body length and very close to the anus, there are well-developed cephalic setae and a long, thick, muscular rectum. In some species, the outer labial and cephalic setae have a joint near the base and are then described as segmented or articulated.  (Cid del Prado-vera et al., 2018).

Per Andrassy, 1981 definition of the genus, primarily terrestrial, often in moist soil environments or on moss in moist environments. Members of the subfamily Monhysterinae, have a single tapered buccal cavity.

 

Females:
Cuticle smooth or very finely striated, with scattered somatic setae.
Body 0.5-1.2 mm.
Outer labial (6) and cephalic (4) setae well developed; lengths <60% of head diameter.
Ocelli absent.
Amphid foveae large, circular, 1-2 head widths from anterior.
Stoma funnel shaped, without teeth or denticles.
Defined by Andrássy as a terrestrial genus, so no aquatic forms with ocelli.
Esophagus cylindrical without terminal bulb.
Rectum muscular, usually >1 abd long.
Vulva at 75-85%, very close to anus, usually within 1-3 abd of anus.
Tail elongate conoid but not filiform, ventrally curved, terminating in a short, conoid spinneret.

  
    Ref: Andrassy (2005); Coomans and Eyualem-Abebe (2006).

Males:  
Males rare in some species, spicules slender, ventrally arcuate, 1.5-2 x abd. Gubernaculum simple, without apophysis.
Median pre-cloacal papillae may be present.
Body size range for the species of this genus in the database - Click:
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Distribution:

Commonly found on tree bark associated with mosses and lichens, or in moist soil environments.

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Feeding:

Based on stomal and pharyngeal morphologies, including the apparent lack of teeth, they are assumed to be bacterivores and to feed on bacteria and possibly substrate ingestion in which the substrate includes bacteria, protozoa, algae, etc. (Yeates et al., 1993). We have observed  occasinal detrital particles and a fungus spore in the intestines of some specimens, suggesting that non-specific ingestion of detritus may occur during the feeding process ( Cid del Prado-Vera,  personal observation).

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Biology and Ecology:

In concordance with the aboveground habitats of many Geomonhystera species, we have observed their very rapid sinusoidal movement in water films. Further, as expected for habitats subject to drying, including
mosses, bark and leaf-litter, they are reported to survive in an anhydrobiotic state in the absence of moisture (Andrássy, 1981).

In contrast to the dry habitats of many of the species of this genus, G. aenariensis was described from thermal waters of fumaroles ranging in temperature from 28 to 40ËšC (Meyl, 1953) and presumably has
physiological adaptations to those environments. Meyl (1953) classified G. aenariensis, among other species from the fumaroles, as “probable thermophiles”. In laboratory experiments he determined that they became coiled and
rigid in water heated to above 37ËšC.

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Life Cycle:

Reproduction in the genus is assumed to be either by parthenogenesis or amphimixis, depending on the presence of males in the species. Of the 22 species that include those described,  seven are known to have males (Cid del Prado-Vera et al., 2018).

For Ecophysiological Parameters for this genus, click 
 

Amphimictic or parthenogenetic.

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Ecosystem Functions and Services:

Free-living soil/terrestrial nematodes.

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Management:

 
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References:

 

Andrassy, I. 2005.  Free-living Nematodes of Hungary, Vol. I. Hungarian Natural History Museum, Budapest

 

Cid del Prado-Vera, I., Ferris, H., Subbotin, S.A. 2018. Six new and one known species of Geomonhystera (Nematoda, Monhysteridae) from moss, an epiphytic plant and soil in Mexico and Ecuador. Zootaxa 4471:76-110.

 

Coomans, A. and Eyualem-Abebe 2006.  Order Monhysterida. Pp 574-603 in Eyualem-Abebe, Traunspurger, W., Andrassy, I. (eds) Freshwater nematodes: ecology and taxonomy.

 

Meyl, A.H. 1953. Beiträge zur Kenntnis der Nematoden Fauna vulkanisch erhitzter Biotope, I. Die terrikolen Nematoden im Bereich von Fumarolen auf der Insel Ischia. Zeitschrift für Morphologie und Ökologie der Tiere, 42:67-116.

 

Yeates, et al. 1993. Feeding habits of soil nematodes. J. Nematology 25:315-331.

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Copyright © 1999 by Howard Ferris.
Revised: November 19, 2024.