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[Strongyloides stercoralis]

The first-stage rhabditoid larvae (L1) of Strongyloides stercoralis are 180-380 µm long, with a short buccal canal, a rhabditoid esophagus and a prominent genital primordium.  These L1 larvae are usually found in stool, as the eggs embryonate and hatch in the mucosa of the small intestine of the host.  They may also be found in soil and cultured feces.

A	B

A, B: Rhabdititoid larvae of S. stercoralis in unstained wet mounts of stool.  Notice the short buccal canal and the genital primordium (red arrows).

C	D

C: Close-up of the anterior end of a rhabditoid larva of S. stercoralis, showing the short buccal canal (red arrow) and the rhabditoid esophagus (blue arrow).  Image taken at 1000x oil magnification.
D: Rhabditoid larva of S. stercoralis in an unstained wet mount of stool.  Notice the short buccal canal and the genital primordium (red arrow).

E	F

E: Rhabditoid larva of S. stercoralis in an unstained wet mount of stool.  Notice the rhabditoid esophagus (blue arrow) and prominent genital primordium (red arrow).
F: Rhabditoid larva of S. stercoralis in an unstained wet mount of stool.  Notice the prominent genital primordium (blue arrow), rhabditoid esophagus (red arrow) and short buccal canal (green arrow).