Localization of the major sperm protein 1 transcript in Onchocerca flexuosa. A probe against major sperm protein 1 of B. malayi (described by  was used as a control since it is unrelated to Wolbachia and has a well-characterized, tissue-specific expression pattern. No labeling was seen in female worms (A). Whereas the spermatocytes within the male testis show strong labeling (B), other stages do not (C). No staining is seen in the lateral chords in any region of the male worm. This result agrees with the localization pattern reported in B. malayi, and it is very different from the in situ hybridization patterns observed with probes against Wolbachia-like sequences. Abbreviations: cu, cuticle; hy, hypodermis; m, muscle; lc, lateral chords; mc, median chords; i, intestine; ut, uterus; t, testis. Scale bar = 50μm.