Pkd21/Pkd21 males are almost completely sterile; they produce motile sperm but these fail to reach the female sperm storage organs.
Pkd21 mutant adults show normal preference for less solid sucrose-agarose food than a harder one (higher agarose conc., same sucrose content) one in a two-way food choice assay.
The gustatory aversion of mutant flies to 6mM camphor in a two way-choice test is not significantly different from that seen in wild-type flies.
Pkd21 males produce motile sperm that are transferred to the uterus but do not reach the female storage organs.
Pkd21 mutant sperm are capable of swimming backwards, both in the uterus and in the seminal receptacle. Although the baseline beat frequency of Pkd21 mutant sperm is similar to wild-type, they fail to demonstrate an increase in beat frequency when released from the uterus (as found in wild-type). This defect is rescued through expression of Pkd2+t1kb. The swimming speed of Pkd21 mutant sperm in the uterus is reduced significantly when compared to wild-type sperm. In addition the dynamic distribution of sperm is altered. Immediately after mating, wild-type sperm cluster near the entrance of the sperm storage organs in the upper third of the uterus, whereas Pkd21 mutant sperm do not show this distribution pattern.
At PSR entry, 15% of Pkd2ko67/Pkd21 sperm are tail-leading, 30% head-leading, and 12% have fold flagella.
96% of Pkd2ko67 / Pkd21 mutant sperm exit the converging tubule with head-leading orientation, as wild type.
In contrast to wild-type sperm, sperm from Pkd2ko67 / Pkd21 males show increased frequencies of head-leading orientation during entry into the proximal seminal receptacle (PSR) and excessive flagellar folding in the PSR lumen. At later time points (1-4 hours after mating), the phenotype is more severe with mostly tangled flagella in the PSR lumen, and the number of mutant sperm that entering the distal seminal receptacle reduced by 100-fold.
Mutant adults show normal avoidance of 1% citronellal in a direct airborne repellent test (DART) assay.
Mutant third instar larvae show the same preference for 17.5[o]C over 14[o]C in a two-way choice test as do wild-type controls.
Pkd21 mutants retain a preference for 18[o]C (i.e. are thermotactic).
Matings between single mutant males and wild-type females results in few or no offspring. The opposite cross results in normal numbers of progeny. Testes from mutant flies display normal architecture with typical abundance of germ cells. The motility of mutant sperm is seen to be indistinguishable from that of wild-type. Mutant males display normal courtship behaviour and normal copulation latency and duration. Mutant sperm are successfully transferred to females. However few or no mutant sperm are detected in the seminal receptacles of the female. Storage of mutant sperm in spermathecae is also reduced. In sperm competition assays, mutant sperm are much less effective at producing offspring than wild-type males when they were the second male to mate with a wild-type female.