Germ cell maturation and cellular associations in the seminiferous epithelial cycle of the chimpanzee

Abstract

Seminiferous tubule architecture, germ cell maturation steps and cellular associations (stages) of the spermatogenic cycle of the chimpanzee ( Pan troglodytes) are resolved. Cross sections of seminiferous tubules usually exhibit 2 to 4 stages, occasionally 1, and rarely 5; stages are not functionally sequential in structurally contiguous regions. The cellular maturation steps are: dark type A stem cell (Ad), pale type A (Ap), type B (B) spermatogonia; resting or preleptotene (Pl), leptotene (L), zygotene (Z), pachytene (P), diplotene (Di) primary spermatocytes; meiotic divisions (M1, M2); secondary spermatocytes (2°S); six developmental stages of the spermatid (Sa, Sb1, Sb2, Sc, Sd1, Sd2) composing spermiogenesis. The germ cell maturation steps characteristic of the six cellular associations (stages I–VI) are: Ad, Ap, B, P, Sa, Sd1 (I); Ad, Ap, B, Pl, P, Sa, Sd2 (II); Ad, Ap, B, Pl, L, P, Sb1 (III); Ad, Ap, Pl, L, P, Sb2 (IV); Ad, Ap, L, Z, P, Di, Sc (V); Ad, Ap, B, Z, P, Di, 2°S, Sc (VI). Surgical pressure trauma causes sloughing of some 2°S spermatocytes and some Sa, Sb1, Sb2, Sd1, and Sd2 spermatids, resulting in missing generations, and disrupts Sertoli cell attachments, affecting germ cell development and associations. In structure and function, chimpanzee spermatogenesis appears most similar to the human.