An electron microscopic study of a 'Sertoli-like' cell in the testis of a barnacle, Balanus.

The organization of a 'Sertoli-like' cell (SLC) is described in the testis of a barnacle, Balanus eburneus. Underlying a relatively thick basal lamina are 'sheet-like' cytoplasmic extensions that develop from the base of the SLC and almost completely enclose the germ cells. Junctional structures are frequently observed between the SLCs and between an SLC and a developing germ cell. Portions of the SLC extend deep into the testis and subdivide into branches. Developing sperm are seen within inpocketings of the plasmalemma of the branches. Noteworthy among the SLC's organelles are large, well-developed mitochondria, an abundant smooth endoplasmic reticulum and masses of glycogen particles. Intercellular bridges are present between germ cells which are at the same stage of development. In some respects the organization of the SLC in B. eburneus is suggestive of that in the Sertoli cell in the testis of vertebrates.