Anatomy and Morphology




Rev. 10/30/19
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Sensory/Nervous System

Nematodes have a variety of sensilla:

(i) Amphids

  • open on or below lips (position of opening is  diagnostic).
  • pouch with sensory neuron.
  • opening is a pore, slit, spiral, etc.
  • contain mucoid material which is, at least in part, a glycoprotein. The glycoprotein component of the amphid mucus differs among nematode species.
  • function as chemoreceptors.
Various shapes of amphid apertures.  More convoluted shapes are thought to enhance sensitivity as chemoreceptors.
From Shuurmans-Stekhoven and De Coninck, modified by Maggenti, 1981.

(ii) Phasmids

pore-like phasmid in lateral field of Rotylenchus robustus

(photomicrograph by I.A. Zasada).

(iii) Other Sensilla

  • elongate setae
  • somatic setae - distributed along body; rare in Secernentea, but occur in Adenophorea

  • shallow pits
  • deirids - in lateral field located anterior to nerve ring (tactoreceptors or chemoreceptors); they are also called cervical papillae; occur in some taxa in Secernentea but not Adenophorea.
  • genital papillae - paired papillae anterior to the cloaca
  • supplements or supplementary organs - ventral side of male just anterior to cloaca;  probably tactile organs during copulation; associated with glands in some taxa.
  • embedded sensilla
  • nerve commissures that appear to be connection points for longitudinal nerves; refractive areas below cuticle (and hypodermis?);  they include:
  • hemizonid - on ventral side in vicinity of the nerve ring, near the excretory pore of Secernentea
  • cephalids - anterior portion of the body, the"neck" region; they may completely encircle the body
  • hemicephalids
  • hemizonion
Adapted Maggenti, 1981 and Hirschmann, 1960.
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