Changes

* The organ is located just in front of the [[Urinary System - Anatomy & Physiology|kidney]] (mesonephros).

* The organ is located just in front of the [[Urinary System - Anatomy & Physiology|kidney]] (mesonephros).

* It is formed at the cranial tip of the male and female gonad during the larval stage.  

* It is formed at the cranial tip of the male and female gonad during the larval stage.  

* Normally it is inactive and contains miniature [[The_Ovary_-_Follicles_- Anatomy & Physiology|follicles]] which have the capability to mature (becoming active).

* Normally it is inactive and contains miniature [[Follicles - Anatomy & Physiology|follicles]] which have the capability to mature (becoming active).

* When the female population is scarce, the Bidder's organ enlarges and produces viable oocytes and then gonadotropins, which stimulate the growth of the Müllerian ducts to form uterus and oviducts.

* When the female population is scarce, the Bidder's organ enlarges and produces viable oocytes and then gonadotropins, which stimulate the growth of the Müllerian ducts to form uterus and oviducts.

* Its internal anatomy consists of two parts:

* Its internal anatomy consists of two parts:

** Central portion: consists of connective tissue and rich in blood vessels.

** Central portion: consists of connective tissue and rich in blood vessels.

** Periphery: consists of the cortex, which contains [[The_Ovary_-_Follicles_- Anatomy & Physiology|follicles]] in various stages of development.  

** Periphery: consists of the cortex, which contains [[Follicles - Anatomy & Physiology|follicles]] in various stages of development.  

** Molecules of various proteins are present in the outer layer of the [[The_Ovary_-_Follicles_- Anatomy & Physiology|follicles]], homologous to the zona pellucida of the ovum.

** Molecules of various proteins are present in the outer layer of the [[Follicles - Anatomy & Physiology|follicles]], homologous to the zona pellucida of the ovum.

=== Male Ducts ===

=== Male Ducts ===