Geraldius bakeri




Rev 05/27/2022

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Geraldius bakeri (Sanwal, 1957), Sanwal, 1971


Chambersiella bakeri Sanwal, 1957

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Morphology and Anatomy:



From Sanwal, 1957

Length 0.8-1.3 mm.; a ~ 20-26; b ~ 3.5-5.6; c = 7.8-10; v = 49.6-53%.
Body gradually attenuated towards both ends, assuming the shape of 'C' when killed by gentle heat.
Cuticle very finely striated and bearing two lateral incisures. Cuticular striations 0.0011 mm.
apart at the middle of the body.
Head not marked off from the rest of the body and without distinct lips.
Cuticle of the lip region with six branched cirri (Figs. 1, la, 7).
Six large labial papillae on the head, one at base of each cephalic cirrus.
Terminal mouth opening leads into a broad stoma (Figs. 1, 7), the walls of which are mostly heavily sclerotized.
Stoma divisible into three regions: anterior, middle, and posterior. Walls of anterior region formed by six curved hooks which present different outlines when viewed in different focal planes (Fig. 1b). These hooks may lie within the head or they may project slightly (Fig. 1a). Walls of middle region of stoma formed by a jointed piece which is distinct from the hooks, there being a visible gap between the two. This part is not uniformly sclerotized. Posterior region of stoma with very lightly sclerotized walls; in some specimens it shows a slight constriction of its walls prior to its junction with the oesophageal lumen (Fig. 4). Whereas the walls of anterior and middle regions of the stoma bound broad chambers,walls of posterior region bound a narrow vase-shaped channel. The three spaces, however, are continuous with each other.
Esophagus with a cylindrical corpus and precorpus but without a median bulb. Narrow isthmus swells into terminal oesophageal bulb which contains a valve.
Esophageal tissue seems to be differentiated into two regions. The tissue of the precorpus and corpus presents a different appearance from that of the isthmus and terminal bulb, there being an oblique line of demarcation
between the two seen at the base of the corpus (Fig. 7).
Well developed cardia between the esophagus and the intestine.
Lumen of intestine wide and its walls filled with globules of granular nature.
Rectum long and narrow. Rectal glands present (Fig. 7).
Nerve ring surrounds isthmus almost midway between the base of corpus and beginning of terminal bulb, but in some specimens it lies further forward almost at the base of the corpus. Amphids open through an elliptical aperture situated behind main chamber of stoma (Figs. 1, 7).
Openings of phasmids situated on slightly raised papilla-like structures symmetrically located on lateral sides of body (Figs. 5, 7).
Excretory pore almost at level of nerve ring or slightly posterior to it, leading into a thin narrow duct directed posteriorly (Fig. 7).
Two ovaries present, opposed and reflexed. Tips of ovaries cross each other. Oocytes arranged in single file. The two uteri run parallel to reflexed ovaries before joining to open into a short and narrow vagina, the walls of
which are lined by refractive cutide continuous with body cuticle.
Vagina opens through a circular vulva placed on top of an elevated vulvar cone. The vulvar cone may be only slightly elevated above the surface of body or the elevation may be quite pronounced. 'The vulvar aperture, however, appears to be circular in all cases (Figs. 5a-5d) , almost equatorial or slightly postequatorial in position.
Tail narrows gradually to a dorsally hooked terminus (Figs. 5, 7).

Length 1.04-1.37; a~21-35; b ~4.3-5.9; c~10.4-11 ; spicules 0.045-0.052 mm.; gubernaculum 0.017-0.02 mm.
Body assumes shape of a 'J' when killed by gentle heat.
Cuticle finely striated, striations being 0.0014 mm. apart at the middle of body.
Head not marked off from rest of body and bears six cirri and six papillae as in female.
Stomatorhabdion arrangement similar to that of female.
Cardia between the oesophagus and the intestine. Nature of lumen of oesophagus, the muscular tissue surrounding stoma and oesophagus, and the valve within terminal bulb is similar to that described in female.
Intestine narrows considerably as it runs parallel to vas deferens.
Cloaca long and narrow lined with thick cuticle. Rectal glands present (Fig. 2).
Single testis extends anteriorly beyond middle of body where it is reflexed. Vas deferens wide and full of sperms (Fig. 2). It narrows posteriorly to open into the cloaca through a short and narrow ejac'ulatory duct.
Two spicules present, of similar shape, and not joined. Gubernaculum present.
Tail curved and ending in dorsally hooked terminus. Posterior region of body bears seven pairs of preanal and eight pairs of postanal papillae. Of the latter, two pairs are lateral, five pairs subvcntral, and one pair subdorsal in position. All preanal pairs subventraI in position.
No caudal alae.

Description from Sanwal, 1957 

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


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From bark of oak tree.
Bank of the Jock River, near Richmond, Ontario, Canada.

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Active bacterial feeder.

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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:

Bacterially-mediated decomposition of organic matter; nitrogen mineralization.


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Sanwal, K.C. 1957. Chambersiellidae n.fam. (nematoda) with emended diagnosis of the genus Chambersiella Cobb, 1920, description of C. bakeri n.sp. and discussion of taxonomic position. Canadian Journal of Zoology 35, 615-621.


Sanwal, K. C. 1971. Geraldius n. gen., Macrolaiminae n. subfam., with a revision of the subfamilies and genera of Chambersiellidae (Nematoda). Canadian J. Zoology 49:965-967.

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Copyright © 1999 by Howard Ferris.
Revised: May 27, 2022 .