Klf15^f06447 homozygous mutants lose pericardial nephrocytes and garland cells during early stages of development so adults are completely devoid of nephrocytes and display defects in heart period (which is longer than in controls due to a longer diastolic interval) and rhythmicity. The end-systolic and the end-diastolic diameters are greater in Klf15^f06447 adults than in wild-type.

Larvae and adults obtained from Klf15^f06447 homozygous parents are missing garland cells and pericardial nephrocytes. Klf15^f06447/Df(1)ED6727 adult females or Klf15^f06447/Y adult males have no pericardial nephrocytes. The absence of nephrocytes seen in Klf15^f06447/Y adult males is rescued by Dp(1;3)DC473 but not Dp(1;3)DC120 or Dp(1;3)DC122.

When fed 0.01% silver nitrate, larvae obtained from Klf15^f06447 homozygous parents show increased mortality compared to controls. However, the lifespan of adults obtained from Klf15^f06447 homozygous parents are identical to controls.

The number and anatomical location of pericardial nephrocytes in Klf15^f06447 mutants at embryonic stage 16 are normal. Similarly, at the L1 stage the phenotype of the heart in Klf15^f06447 mutants is indistinguishable from that in controls. After L1, the pericardial nephrocytes in controls grow considerably in size, whereas this fails to occur in Klf15^f06447 mutants, and by the L3 stage, very few pericardial nephrocytes remain in the mutant. Filtration slits can be readily identified at the surface of pericardial nephrocytes in controls, but no such structures are seen in Klf15^f06447 mutants. Although pericardial nephrocytes were scarce in mutant L3 larvae, those remaining often had a distinctive 'poly-cellular' phenotype. In contrast, the pericardial cells located along the aorta and which form the scutellar pulsatile organs ('wing hearts) appear unaffected in Klf15^f06447 mutants.