Localization of a putative Wolbachia -like aminopeptidase P transcript in adult Onchocerca flexuosa. While the sense RNA probe (negative control) did not label tissues in female (A) or male (C) worms, the antisense probe against isotig12956 (which has sequence similarity to an aminopeptidase P gene from the Wolbachia endosymbiont of Muscidifurax uniraptor) produced a strong signal in both sexes. The hypodermis, lateral chords, median chords, intestine, and the uterine epithelium were intensely labeled in young, non-reproductive females (B). The same probe labeled small, round spermatogonia (D) and larger spermatocytes (E) within the male testis. The large, round, secondary spermatocytes (arrow) were labeled in the transitional region between the testis and vas deferens, whereas the smaller spermatids were not (F). No labeling was observed in the elongated, mature sperm within the vas deferens (G). The labeling of the lateral chords was most intense in the male mid-body and faded towards the posterior end of the males in the vicinity of the mature sperm. Abbreviations: cu, cuticle; hy, hypodermis; m, muscle; lc, lateral chords; mc, median chords; i, intestine; ut, uterus; t, testis; vd, vas deferens. Scale bar = 50μm.