RNA in situ hybridization analysis of expression of the Ams and mts genes in the An. gambiae male reproductive tissues. (A) Hybridization of the Ams antisense probe reveals that abundant transcripts are present in primary and secondary spermatocytes; afterwards the transcripts are gradually degraded, but persist at low level in spermatozoa (small solid arrow). (B) Hybridization of the sense Ams probe produces no signal. (C) Hybridization of the mts antisense probe shows active transcription of the gene in primary spermatocytes and spermatids, and persistence of the transcripts in spermatozoa (small solid arrow). (D) Hybridization of the mts sense probe produces no signal. On each photograph testes are located on the right and accesory glands with ejaculatory duct on the left. Within testis germ cells of the same developmental phase are encased in a single cyst. Unstained apical part of each testis, containing the youngest germ cells, points to the right. The leftmost compartment (encompassed by brackets in insets) represents a sperm reservoir with mature spermatozoa. The low background seen in all samples originates from the color reaction induced by endogenous lysosomal alkaline phosphatases. Note that a stronger background in the accessory gland basal lobes, containing denser granular tissue (arrow), is present in all samples, regardless of the probe used for hybridization.