Biology Reference
In-Depth Information
part of oviduct, namely the genital pore lip (GPL) results from invagination
and caviation of the cortex of uninogenital papillae (UGP) and forms the
oviduct opening (Fig. 20).
Fig. 20.
Development of efferent duct and sperm duct in
Oryzias latipes
. TS of testis of a fi sh
with body length of 12 mm showing the appearance of (A) efferent duct (ED), (B) sperm duct
(SD) and (C) development of urethra (U) scale = 10 µm, (D) TS of the testis to urinogenital pore
in a fi sh with 25 mm body length. mUGP = medulla of urinogenital papillae bl = bladder (E)
For comparison, formation of genital pore bp. (GPL) cavities in female with body length of
24 mm is shown. OC = Ovarian cavity, OD = oviduct, gut = gut scale = 50 µm (from Suzuki
and Shibata. 2004. Zoological Science, 21: 397-406)
Both male and female gonads are bilobed at 10 to 20 dph. Formation
of genital ducts is initiated in both sexes at 20 to 30 dph. Development of
UGP and extra-gonadal ducts is related; the UGP consists of the corex and
medulla. The ventral region of urethra mesenchyme may have an important
role in the formation of the extra genital duct (Fig. 19). Land mark events
in anatomical and histological sex differentiation are briefl y summarized
in Table 17. Onikate (1972) reported that administration of estrone induced
early formation of anterior oviduct in female medaka. But treatment with
