Mechanism of Spermiogenesis

• Histologically, the testis contains germ cells (which form spermatogonia), Sertoli cells (found in direct association with germ cells, which they support physically and nature by modifying the chemical microenvironment), and Leydig cells (their primary function is to produce steroids needed for gametogenesis and expression of secondary sex characteristics).
• The germ cells of the testes undergo spermatogenesis and produce sperm.
• Under a tough membranous shell, the tunica albuginea, the testis of some teleost fish, contains very fine coiled tubes called seminiferous tubules.
• The tubules are lined with a layer of cells (germ cells) that from puberty into old age, develop into sperm cells (also known as spermatozoa or male gametes).
• The developing sperm travel through the seminiferous tubules to the rete testis located in the mediastinum testis, to the efferent ducts, and then to the epididymis where newly created sperm cells mature (spermatogenesis).
• The sperm are produced in spherical structures called sperm ampullae.
• These are seasonal structures, releasing their contents during the breeding season, and then being reabsorbed by the body.
• Before the next breeding season, new sperm ampullae begin to form and ripen.
• During the growth period, the germ cells start to divide and form a large number of primary spermatocytes which are smaller in size than the spermatogonia.
• Primary spermatocyte accumulates a large amount of cytoplasm and nutritive matter and is converted into secondary spermatocyte.
• The secondary spermatocyte undergoes reduction division to produce spermatids which are further reduced in size.
• The spermatids give rise to sperm. The process of metamorphosis of spermatids into sperm is called spermiogenesis.