Bidder's organ
Encyclopedia
Bidder's organ is a spherical, brownish organ
in any member of the family Bufonidae, or simply, toads. The organ is located just in front of the kidney
, or, mesonephros
. It is formed at the cranial tip of the male and female gonad
during the larval stage. Normally it is inactive and contains miniature follicle
s which have the capability to mature (becoming active). Zoologists have experimented with the physiology of the organ by castrating
male toads (removing the testes). In doing so, the Bidder's organ enlarges and produces viable oocyte
s, that is, egg cells, and then it produces gonadotropins, which stimulate the growth of the Müllerian duct
s to form uterus
and oviduct
s. It therefore becomes a fully sexually functional female, which leads some zoologists to conclude that toads are actually paedomorphic.
However, the Bidder's organ only develops into an ovary when testes are removed experimentally or not functioning properly (e.g. due to exposure to endocrine disrupting chemicals). Importantly, females can have a Bidder's organs in addition to true ovaries which suggests that the Bidder's organ might not be a rudimentary ovary. The true function of the Bidder's organ remains a mystery.
It is named in honour of Friedrich Bidder.
, and rich in blood vessel
s, and its periphery consists of the cortex, which contains follicles in various stages of development. Molecules of various protein
s are present in the outer layer of the follicles, homologous to the zona pellucida
of the ovum
. The Bidder's Organ's physiology is unique, having no connection with the sexual changing capabilities of amniotes
(i.e., reptiles, avians, and mammals).
of the intestine between the two mesonephros is the Bidder's organ. It is a conspicuous organ, being colored red, and at the cranial poles of the large testes.
Organ (anatomy)
In biology, an organ is a collection of tissues joined in structural unit to serve a common function. Usually there is a main tissue and sporadic tissues . The main tissue is the one that is unique for the specific organ. For example, main tissue in the heart is the myocardium, while sporadic are...
in any member of the family Bufonidae, or simply, toads. The organ is located just in front of the kidney
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
, or, mesonephros
Mesonephros
The mesonephros is one of three excretory organs that develop in vertebrates. It serves as the main excretory organ of aquatic vertebrates and as a temporary kidney in reptiles, birds, and mammals. The mesonephros is included in the Wolffian body after Caspar Friedrich Wolff who described it in 1759...
. It is formed at the cranial tip of the male and female gonad
Gonad
The gonad is the organ that makes gametes. The gonads in males are the testes and the gonads in females are the ovaries. The product, gametes, are haploid germ cells. For example, spermatozoon and egg cells are gametes...
during the larval stage. Normally it is inactive and contains miniature follicle
Follicle
Follicle may refer to:*Follicle , a small spherical group of cells containing a cavity:** Dental follicle** Hair follicle** Lymph follicle** Ovarian follicle** Thyroid follicle*Follicle...
s which have the capability to mature (becoming active). Zoologists have experimented with the physiology of the organ by castrating
Castration
Castration is any action, surgical, chemical, or otherwise, by which a male loses the functions of the testicles or a female loses the functions of the ovaries.-Humans:...
male toads (removing the testes). In doing so, the Bidder's organ enlarges and produces viable oocyte
Oocyte
An oocyte, ovocyte, or rarely ocyte, is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in the ovary during female gametogenesis. The female germ cells produce a primordial germ cell which undergoes a mitotic...
s, that is, egg cells, and then it produces gonadotropins, which stimulate the growth of the Müllerian duct
Müllerian duct
Müllerian ducts are paired ducts of the embryo that run down the lateral sides of the urogenital ridge and terminate at the Müllerian eminence in the primitive urogenital sinus. In the female, they will develop to form the Fallopian tubes, uterus, cervix, and the upper two-third of the vagina; in...
s to form uterus
Uterus
The uterus or womb is a major female hormone-responsive reproductive sex organ of most mammals including humans. One end, the cervix, opens into the vagina, while the other is connected to one or both fallopian tubes, depending on the species...
and oviduct
Oviduct
In non-mammalian vertebrates, the passageway from the ovaries to the outside of the body is known as the oviduct. The eggs travel along the oviduct. These eggs will either be fertilized by sperm to become a zygote, or will degenerate in the body...
s. It therefore becomes a fully sexually functional female, which leads some zoologists to conclude that toads are actually paedomorphic.
However, the Bidder's organ only develops into an ovary when testes are removed experimentally or not functioning properly (e.g. due to exposure to endocrine disrupting chemicals). Importantly, females can have a Bidder's organs in addition to true ovaries which suggests that the Bidder's organ might not be a rudimentary ovary. The true function of the Bidder's organ remains a mystery.
It is named in honour of Friedrich Bidder.
Anatomy
Its internal anatomy consists of two parts, the central portion, consisting of connective tissueConnective tissue
"Connective tissue" is a fibrous tissue. It is one of the four traditional classes of tissues . Connective Tissue is found throughout the body.In fact the whole framework of the skeleton and the different specialized connective tissues from the crown of the head to the toes determine the form of...
, and rich in blood vessel
Blood vessel
The blood vessels are the part of the circulatory system that transports blood throughout the body. There are three major types of blood vessels: the arteries, which carry the blood away from the heart; the capillaries, which enable the actual exchange of water and chemicals between the blood and...
s, and its periphery consists of the cortex, which contains follicles in various stages of development. Molecules of various protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
s are present in the outer layer of the follicles, homologous to the zona pellucida
Zona pellucida
The zona pellucida is a glycoprotein membrane surrounding the plasma membrane of an oocyte. It is a vital constitutive part of the latter, external but of essential importance to it...
of the ovum
Ovum
An ovum is a haploid female reproductive cell or gamete. Both animals and embryophytes have ova. The term ovule is used for the young ovum of an animal, as well as the plant structure that carries the female gametophyte and egg cell and develops into a seed after fertilization...
. The Bidder's Organ's physiology is unique, having no connection with the sexual changing capabilities of amniotes
Temperature-dependent sex determination
Temperature-dependent sex determination is type of environmental sex determination in which the temperatures experienced during embryonic development determine the sex of the offspring. It is most prevalent and common among amniote vertebrates that are classified under the reptile class, but is...
(i.e., reptiles, avians, and mammals).
Location in a dissected toad
The ideal specimen for dissection is Bufo marinus, or Giant Cane Toad. In the male toad, lift the intestine leftward. In the mesenteryMesentery
In anatomy, the mesentery is the double layer of peritoneum that suspends the jejunum and ileum from the posterior wall of the abdomen. Its meaning, however, is frequently extended to include double layers of peritoneum connecting various components of the abdominal cavity.-Mesentery :The...
of the intestine between the two mesonephros is the Bidder's organ. It is a conspicuous organ, being colored red, and at the cranial poles of the large testes.