On the other hand, the presence of hermaphrodite scallops developing only or mostly a female gonad
might be the result of inheriting the two X-chromosomes from the nondisjunction (XXX), as well as possibly from random mutations in other key-genes involved in the sex-determination cascade.
Serial sections of female gonads
were used to analyze the relative density of ovarian structures.
For example, in humans signs of sexual dimorphism in the male appear at 6 weeks of gestation, whereas the female gonad
resembles the indifferent gonad until the sixth month of pregnancy.
In his De Mulierum Organis Generatione Inservientibus, De Graaf provided the first thorough description of the female gonad
and established that it produced the ovum.
At the beginning, female gonad
development was minimal in all treatments with high frequency of inactive (50%) and spent (25%) mussels (Fig.
We found that these variations of gonad serotonin concentration (ng/g) are observed in both male and female gonads
and that for each gonadal stage serotonin concentrations were not significantly different between males and females.
The female gonad
first appears as an off-white and translucent band of tissue that begins to extend slightly outward from the digestive gland, accumulating mass as follicles thicken and oogonia develop into primary previtellogenic oocytes (<10 [micro]m) along the germinal epithelium (Fig.
There was a weak, but insignificant, correlation between the total heavy metal concentrations in sediments and the sums of mean female gonad
lesions (r = 0.
The protruding externa is the only externally visible part of the parasite and is its reproductive component; when young, it contains the female gonad
and two empty sperm sacs.
Photomicrograph of a histological section of (A) indeterminate, (B) developing, (C) ripe, and (D) spawning stages of a female gonad
in Anudara granosa.
Percent agreement between macroscopic and microscopic female gonad
stages was calculated to evaluate the accuracy of macroscopic staging (used in all previous studies of tautog reproductive biology).
For some experiments, gonad collecting tubules (with adjacent connective tissue) were dissected manually from the ripe male or female gonad
and the excised tissue was microscopically examined to definitively determine the absence of gametes (spermatozoa or oocytes) in the tubule lumen.
Exposure of a monosex population of male carp to 17[beta]-estradiol (10 [micro]g/L) for 90 days resulted in phenotypic female gonad
containing oviduct and oocytes (10), and in Japanese medaka (Oryzias latipes), exposure to 17[beta]-estradiol (1 [micro]g/L) for 90 days beginning 1 DPH resulted in complete feminization (30).
The male gonad is smaller than the female gonad
, therefore the male fish requires less stored energy for gonadal development and it may start to mature earlier than females.
Male gonad retains its creamy white color whereas female gonad
becomes yellow when ripe (Fig.