Gracilacus hamicaudata




Rev 02/13/2023

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           Gracilacus hamicaudata Cid & Maggenti, 1988

      Paratylenchus hamicaudatus

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Morphology and Anatomy:

Gracilacus hamicaudata: Female body
From Cid del Prado and Maggenti, 1988
Female:  Mature females are obese at midbody but posteriorly the body is constricted and hook-shaped with a rounded tail terminus.
Striations of cuticle conspicuous only in anterior and posterior regions.
Cephalic region with four submedian lobes and a circular oral disc.
Vulval-lips protrude and the lateral field is marked with four lines.
Eggs are partially embedded in a gelatinous matrix.

Male: Unknown.
Juvenile: Stylet present, esophagus well developed.

Posterior end of female (SEM).  Photograph: I. Cid del Prado

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

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Northern California


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Economic Importance:

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Feeds in colonies under the root cortex and apparently anchored to enlarged feeding site cells in the phloem parenchyma of secondary roots.  The nematode bodies are not exposed to the root surface. Feeding induces cell wall thickening.  Giant cell feeding sites are formed in the parenchyma tissue of the vascular cylinder associated with aggregations of nematodes.

At the feeding site, pericycle cells increase in number then collapse and die (Cid del Prado and Maggenti, 1988)

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Type host: Redwood: Sequoia sempervirens

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

Female attaches to feeding sites in vascular parenchyma by the stylet. Female body swells as gonads mature. Eggs are deposited in a gelatinous matrix which surrounds the female, eggs and and newly hatched J2s under the root cortex (Cid del Prado and Maggenti, 1988).


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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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Cid del Prado Vera & Maggenti, A. 1988. Description of Gracilacus hamicaudata sp. n. (Nemata: Criconematidae) with biological and histopathological observations.  Revue de Nematologie 11:29-33.

Raski, D.J. 1976. Revision of the Genus Paratylenchus Micoletzky, 1922 and Descriptions of New Species. Part III of Three parts--Gracilacus. J. Nematology 8:97-115.

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Copyright © 1999 by Howard Ferris.
Revised: February 13, 2023.