Anatomy and Morphology




Rev. 01/01/20
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Reproductive System

One or two testes (monorchic/diorchic), one or two ovaries (monovarial/diovarial).

(i) Male system:

Single testis (monorchic) or two testes (diorchic), 

 spicules, gubernaculum, caudal alae are all of diagnostic value.


AEnoplus sp., Class Enoplea, Subclass Enoplia - paired testes, opposed.
BTobrilus sp., Class Enoplea, Subclass Enoplia - paired testes, opposed.
CRhabditis sp., Class Chromadorea, Subclass Chromadoria - single testis, reflexed.
(Modified from Maggenti (1981), after Chitwood)
Dorylaim testes
Dorylaimida: paired, opposed testes


Spicules - paired, may be fused at tip.

Generally crescent-shaped, with distinct regions, and a  cytoplasm core supplied with nerves.  

Their function is to spread vulva to allow entry of sperm.  

(Modified from Maggenti, 1981)


Size and shape of spicules varies greatly among taxa.

The spicules provide useful diagnostic characters. 

(Modified from Maggenti, 1981)


If present is a guiding structure for  spicules. Varies in shape.

Often grooved.

(Modified from Maggenti, 1981)

The spicules may merely ride against the gubernaculum when extended from the cloaca, or may slide along a track formed by the gubernaculum.

(Modified from Maggenti, 1981)

Supplements - glands of secretion and attachment.  Ventromedian supplements have copulatory function.

Male, Order Dorylaimida.  Photomicrograph by I.A. Zasada

Rays - genital papillae embedded in caudal alae in some forms (sensory, tactile function?).
Caudal alae (bursa) - cuticular in nature, see description under Cuticle.
Sperm  - generally non-flagellate, amoeboid.

(ii) Female system:

  • Germinal zone:  region of active cell division
  • Growth zone: region of egg growth
  • Spermatheca: region where sperm are stored after copulation;  may not be present or may be absent in parthenogenic species
  • Crustaformeria or quadricolumella:  region of specialized cells that secrete egg membrane
  • Uterus:  contains developed eggs prior to egg laying
  • Vagina:  muscular passage to exterior, lined with cuticle near vulval opening
  • Vulva:  opening of reproductive tract to exterior, may be variously protected by cuticular flaps or extensions of the vulval lip (epiptygma)


Two other configurations of the female reproductive system occur:
  • Monovarial, opisthodelphic (uterus directed posteriorly, vulva usually located in anterior region of nematode)
  • Diovarial, prodelphic (vulva usually located at posterior of swollen female)

Additionally, ovaries may be variously reflexed and enlarged

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