XY animals carrying dsx^F.Hsp83 in an otherwise wild-type background develop as males and are fertile with no overt effects on germline morphology. XY animals carrying dsx^F.Hsp83 in a dsx¹/dsx⁴³ background develop as pseudofemales. Their external morphology closely resembles wild-type females, however, their gonads are much less well developed. The gonads are attached to an oviduct, but are much smaller than normal. Several small, disorganised, capsule-shaped chambers filled with undifferentiated germ cells are present.

dsx^F.Hsp83 has no effects on female viability in a wild-type background at 25^oC or 29^oC.

Subtle effects on viability (6-8%) are seen at 25^oC and 29^oC in

flies carrying dsx^F.Hsp83 in a dsx¹/dsx⁴³ background.

At 18^o to 25^oC, the genitalia are incompletely feminised, although

they are clearly more feminised than the intersexual genitalia of XX

dsx¹/dsx⁴³ animals. The male genital arch, which is normally

found in XX dsx¹/dsx⁴³ animals, is missing although the pigmentation

of abdominal segments A6 and A7 is similar to that observed in XX dsx¹/dsx⁴³

animals. The flies have mature, overfilled ovaries containing multiple

late-stage eggs. At 29^oC, pigmentation and external genitalia of

females carrying dsx^F.Hsp83 in a dsx¹/dsx⁴³ background

resembles that of wild-type females. 10-15% of the females are rescued

to fertility by a single copy of dsx^F.Hsp83. The remaining females

are sterile and do not lay eggs. The reason for this sterility is

unclear; the external genitalia and internal structures of the gonad

closely resemble wild-type and the ovaries are morphologically normal

and filled with many late-stage eggs.

Males carrying one copy of dsx^F.Hsp83 in a wild-type background

are, in general, morphologically normal and fertile. At low temperatures,

the only alteration is the occasional appearance of sternite bristles

with female-like characteristics in abdominal segment 6. At 25^o

or 29^oC, the male-like genitalia are occasionally rotated. A 34%

reduction in male viability is seen at 29^oC. The courtship index

of males carrying dsx^F.Hsp83 is not significantly different from

wild-type. The duration of copulation shows a significant, slight

decrease compared to that of wild-type males. Males carrying dsx^F.Hsp83

do not court wild-type males, however, wild-type males court males

carrying dsx^F.Hsp83, and males carrying dsx^F.Hsp83 court each

other with significant courtship indices. The pheromone profile of

XY flies carrying dsx^F.Hsp83 is dramatically altered compared to

wild-type.

Males carrying dsx^F.Hsp83 in a dsx¹/+ background show no effect

on abdominal pigmentation, but there is an increase in the frequency

of genital rotation and other gross abnormalities of the genitalia

compared to males carrying dsx^F.Hsp83 in a wild-type background.

The number of bristles on abdominal segment 6 is also increased.

These males have male-specific accessory glands and the gonads develop

as sperm-producing testes. The number of sex comb teeth is reduced

compared to dsx¹/+ males. These males court less frequently and

less aggressively than dsx¹/+ controls, and when they do court

it is not sustained for long periods of time.

XY flies carrying dsx^F.Hsp83 in a dsx¹/dsx⁴³ background

are transformed into pseudofemales at 25^o or 29^oC. Externally,

these pseudofemales have female abdominal pigmentation and female genitalia

and lack sex combs. This external feminisation is fully penetrant

with invariant expressivity. Internally, although a uterus is present

and male-specific structures such as the accessory glands are absent,

the germline and surrounding soma is underdeveloped; there are no distinct

ovarioles or developing egg chambers - only amorphous germline/soma

cell clusters are seen. There is a complete loss of sex combs (they

are transformed into female bristles). Viability is reduced by 38-40%

compared to dsx¹/dsx⁴³ males. These pseudofemales show little

interest in females and perform only early mating behaviours (orientation,

tapping, wing extension and vibration). Unlike wild-type females they

continue to move around the chamber during copulation and flick their

wings in an apparent attempt to dislodge the male.

Df(2R)en-B/ix¹, dsx^F.Hsp83 has male fertile phenotype

Df(2R)en-B/ix¹, dsx^F.Hsp83 has wild-type | male phenotype

Df(2R)en-B, dsx^F.Hsp83, ix¹ has male fertile phenotype

Df(2R)en-B, dsx^F.Hsp83, ix¹ has wild-type | male phenotype