phl^400B8 mutants are lethal in larvae, but such flies carrying phl^hs.PD can survive to fertile adults by using daily heatshocks. If heatshocks are withdrawn on eclosion, testes from 5 day old males are indistinguishable from controls. By day 7 however, almost all mutant testes show great proliferation centre expansion. This is due to excess, early stage germ cells and continues such that on day 15 testes are filled with these cells at the expense of post-mitotic cells. Unbranched fusomes are found in may cells even those located some distance from the hub, where in wild-type testes, only branched fusomes interconnecting secondary spermatogonia are found. Although branches fusomes are found, these fusomes usually appear only after an intervening region containing many excess cells that have only spheroid fusomes. These excess germ-cells do not result from an increased frequency of germline stem cell divisions, as the M-phase index for the tier of cells adjacent to the hub in mutant testes is almost identical to that in wild-type. Homozygous mutant germ-line clones appear to be completely wild-type.

Homozygous embryos exhibit defects in posterior pattern. Injection of wild type RNA fails to rescue the defects.

Class 1 allele: Unrescued embryos (lacking maternal and zygotic phl activity) fail to differentiate into structured embryos and degenerate around 7 hrs of development. Rescued embryos (carrying wild type phl from their father) miss most structures posterior to abdominal segment 6 or 7 and anteriorly a portion of the cephalopharyngeal skeleton, labral sense organ and medial tooth are deleted. fkh expression (in wild type evident in hindgut, Malpighian tubule(s) and anal pads) entirely absent from class 1 embryos. Expression of tll, hkb, hb, fkh absent from both rescued and unrescued embryos, 7th ftz stripe deleted and 6th ftz stripe variably deleted/expanded. Conclude from 0% to 20--25% EL of blastoderm embryos deleted in class 1 alleles.