Expression of hephScer\UAS.cSa under the control of Scer\GAL4nos.UTR.T:Hsim\VP16 (the animals are initially raised at 18oC and are then shifted to 29oC as adults) results in a complete loss of early germ cells (stem cells, gonialblasts and spermatogonia) in the testis. The affected testes contain mostly differentiated spermatids with elongated spermatid bundles often extended all the way up to the testis tip. Animals expressing hephScer\UAS.cSa under the control of Scer\GAL4nos.UTR.T:Hsim\VP16 at 21oC occasionally contain testes with clusters of about 16 small cells.