SpermatoStages

A model of the seminiferous epithelium cycle

Track germ cells through spermatogenesis — forward and backward in time — across more than 20 species, from rat and mouse to human, bull, horse, and many more.

SpermatoStages is an interactive, web-based teaching and research tool for reproductive biology, toxicology, pathology and veterinary/medical science. Pick a species, pick a germ cell, and predict where it will be after any number of days. Useful for identifying target cell types in toxicity studies, planning sample collection, and teaching the kinetics of spermatogenesis — the cycle, mitosis, meiosis, and germ cell differentiation.

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What it does

• Stage grids (maps of the seminiferous epithelial cycle) for each species, strain, and breed
• Forward and backward prediction of germ cell positions across the cycle
• Adjustable cycle length and stage frequencies per species
• Stage histology images with cell labels and schematic drawings
• Interactive teaching tool for the kinetics of spermatogenesis and the seminiferous epithelium cycle
• Runs in any modern browser — Mac, Windows, Linux, iPad, Chromebook

Built on the work of

Hess RA (1990). Quantitative and qualitative characteristics of the stages and transitions in the cycle of the rat seminiferous epithelium: light microscopic observations of perfusion-fixed and plastic-embedded testes. Biology of Reproduction 43(3): 525–542.

Hess RA, Chen P (1992). Computer tracking of germ cells in the cycle of the seminiferous epithelium and prediction of changes in cycle duration in animals commonly used in reproductive biology and toxicology. Journal of Andrology 13(3): 185–190.

About the name

SpermatoStages is the web-based continuation of a program that has been in development for nearly four decades. The earliest version was designed by Dr. Rex Hess and written in Turbo C for MS-DOS by Dr. Paul Chen beginning in 1988, with input from Dr. Yves Clermont (whose 1952 work with Leblond established the 14-stage system this program models). It was published as Hess & Chen 1992, re-designed by Hess and rewritten for Windows by David Scott in 1994 and for Mac computers by Daniel Pape in 1995. All rights, title and copyright ownership were purchased by Hess, and U.S. Copyright Registration Number TX0006361724 was assigned on 2006-03-17. The program was rewritten in 2026 for the web as SpermatoStages. The name has been changed from STAGES to distinguish this program from other software using the STAGES name.