Testes measures of sterile and fertile males
Males from each strain as well as sterile hybrid males were collected
and kept in vials containing CYAM medium with no more than 20 males per
vial to avoid crowding. The males were aged to either 5 or 10 days old
before being frozen to preserve them. Frozen males were allowed to
briefly thaw over the course of a few minutes and dissected in a drop of
1× PBS. Forceps were used to grip the thorax while the other pinched the
male’s abdomen just above the aedeagus. Then, by simply pulling on the
gripped abdomen the entire male’s reproductive tract was pulled out into
a drop of 1×PBS. The testes were isolated using dissecting pins and
moved onto a fresh drop of 1×PBS. Testes images were captured using an
inverted Olympus CKX41 microscope and the image processing and analysis
software Image J (https://imagej.nih.gov/ij/) was used to measure an
area towards the basal end of the testes where mature sperm is found and
which we refer to as the seminal vesicle. The area can be approximately
identified by an apical pinch followed by a basal pinch or torsion. One
testis from each male was measured.