Rhizonemella sequoiae




Rev 09/14/2023

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          Rhizonemella sequoiae (Cid del Prado Vera, Lownsbery & Maggenti, 1983) Andrassy, 2007

Type speciwes of the genus.


Rhizonema sequoiae Cid del Prado Vera, Lownsbery & Maggenti, 1983

Andrassy (2007) provided the nomen novum because the name Rhizonema was already in use in the Hydrozoa:: Rhizonema Clark (1877). As of 2019, this is the type and only species of the genus.

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Morphology and Anatomy:


Female:  No cyst stage.  

Body globose, with prominent neck and terminal cone.  

Cuticle thick, wavy; entire body annulated, except terminal cone. 

D-layer absent.  No subcrystalline layer.

Vulva and anus situated on terminal cone which has a thickened cuticle.  

Phasmids not observed.  

Eggs retained in female body together with hatched second-stage juveniles.  

Rhizonemella sequoiae female, with eggs retained, embedded in the vascular tissue of a redwood (Sequoia) root.

Photographs by Ignacio Cid del Prado Vera, April 2005; Dec. 2017.


Males:  Body twisted.  

Lateral field with four lines.

Spicules nearly straight, pointed, posteriorly directed.

Cloacal tube well developed.

No phasmids.  

Second-stage juveniles: Lateral field with four lines. 

Esophageal glands filling body cavity.  

Tail conical-pointed, with long, hyaline, terminal part. 

Phasmids with lens-like structure.  

[Ref: Luc, Maggenti & Fortuner,  (1988).]

 Reported median body size for this species (Length mm; width micrometers; weight micrograms) - Click:

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Coastal redwood forest, Marin County, California.  Type locality is Lagunitas Lake, San Rafael, CA.
Ignacio Cid del Prado and Sergei Subbotin at type locality, April, 2005.
Collecting redwood roots.
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Economic Importance:


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Nurse cell system: A single, giant cell with a giant nucleus.      

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Sequoia sp., Laurel.  

For an extensive host range list for this species, click

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Life Cycle:

Ecophysiological Parameters:

For Ecophysiological Parameters for this species, click If species level data are not available, click for genus level parameters


Nine month duration, optimum temperature 18C.  At 25 C, only males are produced and above 25 C there is no reproduction (Cid del Prado Vera, pers. comm.).

Eggs are retained in female body together with hatched second-stage juveniles.  There is no cyst stage, female body does not harden.

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Host Plant Resistance, Non-hosts and Crop Rotation alternatives:

For plants reported to have some level of resistance to this species, click



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Andrassy, I. 2007. Free-living Nematodes of Hungary Vol II.Hungarian Natural History Museum, Budapest. 496p.

Cid del Prado Vera, and B. F. Lownsbery. 1984. Histopathology and host range studies of the redwood nematode Rhizonema sequoiae. Journal of Nematology 16:68-72.

Cid Del Prado Vera, I., B. F. Lownsbery and A. R. Maggenti. 1983. Rhizonema sequoiae n. gen. n. sp. from coast redwood Sequoia sempervirens (D. Don) Endl. Journal of Nematology 15:460-467.

Luc, Maggenti & Fortuner, Rev. Nematol. 11(2):159-176 (1988).


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Copyright © 1999 by Howard Ferris.
Revised: September 14, 2023.