Eyespot and other pigments in nematode esophageal muscle cells

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Abstract
Nematode eyespots are recognizable as paired spots of granular, dense pigment localized within anterior muscle cells of the esophagus, or projections thereof. The 10 species studied here include a variety of morphologies and colors. A third, less dense, patch of eyespot pigment was observed in six of the species. Of the species for which eggs could be obtained, eyespots of five developed 2–5 days prior to larval hatching, but those of one, Symplocostoma sp., appeared only in males just prior to the last moult. Chemical properties and absorption spectra of eyespot pigments of the more common species were investigated. The brown eyespot pigment of Enoplus spp. resembles mature eumelanin, and the purplish pigment of two other species is probably incompletely polymerized eumelanin. Properties of less stable, reddish eyespot of four species are unlike melanins or other known pigment classes.Another granular esophageal pigment was observed in 4 of the 10 species. Unlike eyespot pigment it is distributed along the length of the esophagus and is absent at hatching, accumulating with age. That of Enoplus spp. resembles hemosiderin in chemical properties. Also, hemoglobin was identified in nonpigmented regions of the esophageal muscle and in the hypodermal chords of two species.
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