Histodytes microocellatus		Contents		Rev 02/20/2025
		Classification		Biology and Ecology
		Morphology and Anatomy		Life Cycle
Return to Histodytes Menu				Ecosystem Functions and Services
		Distribution		Management
Return to Guyanemidae Menu		Feeding		References
		Go to Nemaplex Main Menu		Go to Dictionary of Terminology

Classification:

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Morphology and Anatomy:

• Anteriorly bilaterally symmetrical with a circular buccal aperture surrounded by a circular and slightly raised rim.
• Seven pairs of cephalic papillae in two circles; the inner circle of two pairs of large mammiliform papillae located dorsally and ventrally and a pair of small papillae, one on each side of the oral aperture. The outer circle has two pairs of relatively non-prominent papillae, located close to the mamilliform papillae of the inner circle, and  two lateral papillae surrounded by a slightly raised cuticular ring.
• Amphids at the center of the two triangles formed by the three pairs of lateral papillae.
• Eesophagus with a short, narrow, muscular anterior and a longer, thicker glandular posterior which penetrates a short distance into the intestine and  opens via a flask-shaped valve.
• Nerve ring is located at 2/3 of length of  muscular esophagus;  excretory pore is posterior to the nerve ring .

Histodytes microocellatus: male tail with spicules Drawing from Aragort et al., 2002
Males:   Cuticle smooth  except for the ventral posterior region where it is ornamented with minute rounded excrescences. Spicules thin, long, smooth; slightly unequal in size. Caudal region with ten pairs of papillae: three ventral precloacal pairs, one lateral cloacal pair, six ventral postcloacal pairs No caudal alae.	Female:   Size about 28 times larger than the male Cuticle without ornamentation. Vulva circular and small but functional, located far posterior to the end of the esophagus  at about 20% of body length from anterior. Vagina sinuous, with muscular walls. Didelphic, anterior branch shorter than posterior. Gravid adults may have 90% of body occupied by larvae. No functional anus: a narrow rectal canal  at the caudal end, but this disappears without an anal orifice. Tail thick and blunt-ended  with a small mucron.  L1 larvae with a triangular tooth in the apical position Ref: Aragort et al., 2002
Reported median body size for this species (Length mm; width micrometers; weight micrograms) - Click:

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Distribution:

Described from the gill, heart, kidney, spleen and gonad tissues of Raja microocellata (the small-eyed skate) from the continental shelf off the estuary of Muros y Noia (north-western Iberian Peninsula)

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Feeding:

In infected tissues (heart, kidney, gills, spleen, gonads), females of H. microocellatus are located in capsules formed by several concentric layers of connective tissue, with abundant erythrocytes, lymphocytes and eosinophils at the lesion periphery. Abundant larvae are surrounded by eosinophils.

Significant inflammatory reaction in the affected tissues. Aragort et al (2002) conclude that the nematodes induce haemorrhage and significant tissue damage.

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Biology and Ecology:

  Considered to have a strong host specificity having only been detected in the elasmobranch skate, Raja microocellata. It was not present in three other species of Raja. 

Males were observed only in the gills, while females were in the gills, heart, kidney, spleen and gonads. Larvae were found in all viscera and in blood vessels (Aragort et al., 2002).

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Life Cycle:

Ecophysiological Parameters:

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Ecosystem Functions and Services:

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Management:

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References:

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Copyright © 1999 by Howard Ferris.
Revised: February 20, 2025.