Trischistoma veracruzense




Rev: 11/19/2019

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Trischistoma veracruzense Cid del Prado, Ferris and Nadler, 2010

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Morphology and Anatomy:

Body slender, curved dorsally in the posterior part, with the tail tip dorsally reflexed.
Cuticle smooth, varying in thickness but generally thin (1.0-1.5 μm).
Lip region asymmetric and continuous with the body contour, 11-14 μm wide.
Cephalic sensillae in three whorls, the first composed of six very small inner labial papillae, the second of six outer labial setae 7-10 μm long, the third of four slightly shorter cephalic setae 5-6 μm long and separated from the second whorl by 5-7 μm .
Amphid apertures vary from slightly posterior to slightly anterior to cephalic setae, 11-16
μm  from the anterior end.
Stoma with small dorsal tooth, positioned within an invagination of the stoma wall, and two minute subventral denticles anterior to the dorsal tooth.
Stoma walls not thickened.
Pharynx cylindrical and muscular; sphincter muscle cells between pharynx and intestine are not enlarged into a cardia.
Vulva with lips protruding very slightly and without sclerotised structures.
One ovary, prodelphic and outstretched or reflexed.
Most females with conspicuous oval-shaped sperm cells in the uterus and post-uterine sac.
Post-uterine sac is almost as wide as the body and 94-170 μm long.
Taill tip reflexed dorsally into a U-shape with a small spinneret; tail tip twisted in some specimens.

Cid del Prado et al., 2010.


Trischistoma veracruzense Female. (A-E, G-H). A: Anterior region; B: Cervical region; C: Oesophago-intestinal valve; D: Posterior region; E: Lip region; G: Posterior region; H: Tail. Male. (F, I). F: Lip region; I: Tail.  Drawings from Cid del Prado et al. (2010).

Abundant,  smaller and more slender than female.
Lip region asymmetric and continuous with the body contour.
Inner labial papillae very small, the outer labial setae 9-10 μm long.
Cephalic setae slightly smaller and thinner than the outer
labial setae,  5-6 μm  long.
Outer labial and cephalic whorls of setae are 5-7 μm apart.
Amphid apertures slightly posterior to cephalic setae.
Stoma walls not thickened.
Sphincter cells between pharynx and intestine not enlarged into a cardia.
The single testis is outstretched.
Spicules slightly curved, not surrounded by a muscular pouch.
Gubernaculum very thin.
Tail twisted dorsally, strongly in most specimens, ending in a hyaline region with a small spinneret.

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


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Type locality: Soil around roots of trees in a tropical forest in San Fernando, Municipio de Soteapan, Los Tuxtlas, Estado de Veracruz, Mexico (N 18° 18.58´; W 94° 53.45´), 1040 m above sea level.

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Nematodes of the family Tripylidae are generalist predators of small aquatic and soil organisms. Many authors have commented on the freshwater and
wet soil in which these nematodes are found, and on the nature of their prey based on observation of intestinal contents or from behavior. Among the recorded prey, as reviewed and collated by Small (1987), are nematodes, rotifers and protozoa (Cid del Prado et al., 2012). 

Nematodes in the Tripylidae attach to soil particles or other substrate via adhesive material extruded from the caudal glands through the spinneret.  Thus anchored, the body moves quite reapidly in water films, sometimes thrashing vigorously.  This behavior has at least three possible purposes: 1. to make tactile contact with prey organisms, 2. to create currents that stir up the sediment and potential prey organisms settled therein, and 3. to anchor the nematode in currents of moving water.

Interestingly similar attachment and feeding behavior occurs in other nematode groups  that, based on most characters, appear to be only distantly related.  For example, the generalist predators of the Tripylidae are in the Class Enoplea, Subclass Enoplia, Order Enoplida, the specialist predators of other nematodes in the Mononchidae are in the Class Enoplea, Subclass Dorylaimia, Order Mononshida, while the bacterivorous Plectidae are in the Class Chromadorea, Subclass Chromadoria, Order Plectida, according to the phylogeny proposed by De Ley and Blaxter, (2002, 2004).

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Biology and Ecology:

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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

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Ecosystem Functions and Services:

Predation and population regulation of prey species.

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Brzeski, M.W. (1965): On the identity of Trischistoma Cobb and Tripylina Brzeski. Nematologica 11:449.

Cid del Prado, I., H. Ferris and S.A. Nadler. 2010. Soil inhabiting nematodes of the genera Trischistoma, Tripylina and Tripyla from México and the USA with descriptions of new species. Journal of Nematode Morphology and Systematics 13-28-49.

Copyright © 1999 by Howard Ferris.
Revised: November 19, 2019.