Intercellular bridges and factors determining their patterns in the grasshopper testis.

Intercellular bridges joining cells contained in cysts of Chortophaga viridifasciata testes were studied with light and electron microscopy. Preparations consisted of expressed whole cells (living, or fixed and stained) as well as sections. The secondary spermatogonia of each cyst are joined centrally by persisting fused interzonal bodies (fusomes) of incompletely cleaved cells. Shifts in cell orientation during anaphase are apparently responsible for central as opposed to chain linkage of cells. In the primary spermatocytes, the central fusome is replaced by a chain linkage, apparently resulting from the breakdown of the fusome into its original interzonal body components. Intercellular bridges are also present in spermatids, but there is no evidence to indicate the time of their formation (in the immediately preceding meiotic divisions or in the secondary spermatogonial divisions). The function of the compact centrally situated fusome in the secondary spermatogonial cyst is discussed as it relates to synchrony, number of cell divisions, spermatodesm formation, and fertility.