Spermatiden

Spermatiden are the haploid cells formed during spermatogenesis in the testes as the products of meiosis II from secondary spermatocytes. In most vertebrates, each secondary spermatocyte gives rise to two spermatids, and a single primary spermatocyte yields four haploid spermatids in total. These cells are located within the seminiferous tubules and remain in contact with Sertoli cells as they complete their differentiation.

At this stage, spermatids typically appear round to elongated but have not yet acquired the full morphology of mature sperm. They contain a haploid genome with highly condensed chromatin and are connected to neighboring germ cells and Sertoli cells via cytoplasmic bridges, which coordinate their development.

Spermiogenesis, the next phase of differentiation, drives the transformation of spermatids into mature spermatozoa. During this process, the acrosome forms from the Golgi apparatus, the nucleus undergoes extensive condensation and elongation, histones are replaced by protamines, and a flagellum develops for motility. Mitochondria reorganize into a midpiece, while excess cytoplasm is removed and shed as residual bodies, typically phagocytosed by Sertoli cells.

The mature spermatozoa are released into the lumen in a step called spermiation and subsequently acquire additional functional maturation in the epididymis. Spermatiden thus represent a transient, essential stage in male gametogenesis; defects during their formation or differentiation can contribute to male infertility. The term Spermatiden is the plural form in several languages for what are called spermatids in English.