A permeability barrier in the testis of an insect Triatoma: A freeze-fracture and lanthanum tracer study.

In vertebrates, the testicular permeability barrier has been the subject of numerous studies. Some recent observations also indicate the existence of such a barrier in some invertebrates, e.g. insects and worms. With the aim of determining whether the morphological features of the blood-testis barrier generally found in vertebrates can be extended to other animals, we studied the testis of the insect Triatoma infestans using electron-dense tracers and freeze-fracture techniques. This organ is divided into cysts timed in synchroneous maturation. The intercellular tracer (lanthanum hydroxide) freely penetrates the basal areas of the seminiferous epithelium surrounding spermatogonia and spermatocytes devoid of synaptonemal complexes (pre-leptotene and leptone). Zygotene spermatocytes indicate the establishment of the barrier. Freeze-fracture techniques exhibit the morphological correlate of the barrier consisting of 9-10 nm particle rows on the P faces of the Sertoli cell membranes. These rows are relatively loose showing an undulating disposition and correspond to the septate junctions found in thin sections. The percolation of intercellular tracers demonstrates that septate junctions between the basal membraneous areas of Sertoli cells possess the barrier properties.