Bidder's organ is a spherical, brownish

organ Organ may refer to: Biology * Organ (biology), a part of an organism Musical instruments * Organ (music), a family of keyboard musical instruments characterized by sustained tone ** Electronic organ, an electronic keyboard instrument ** Hammond ...

in most members of the family

Bufonidae {{Cat main, Toad This category contains both species commonly called toads, and the true toads from the family Bufonidae {{Cat main, Toad This category contains both species commonly called toads, and the true toads from the family Bufonidae {{Cat m ...

(true toads). The organ is located just in front of the

kidney The kidneys are two reddish-brown bean-shaped organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about in length. They receive blood from the paired renal arteries; blood ...

, or

mesonephros The mesonephros ( el, middle kidney) is one of three excretory system, 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 mesone ...

. It is formed at the

cranial Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pro ...

tip of the male and female

gonad A gonad, sex gland, or reproductive gland is a mixed gland that produces the gametes and sex hormones of an organism. Female reproductive cells are egg cells, and male reproductive cells are sperm. The male gonad, the testicle, produces sper ...

during the larval stage. Its main function appears to be endocrine, taking part in regulating sex hormones. Normally, it contains miniature egg follicles which have the capability to mature (becoming active). Zoologists have experimented with the physiology of the organ by

castrating Castration is any action, surgical, chemical, or otherwise, by which an individual loses use of the testicles: the male gonad. Surgical castration is bilateral orchiectomy (excision of both testicles), while chemical castration uses pharmaceu ...

male toads (removing the

testes A testicle or testis (plural testes) is the male reproductive gland or gonad in all bilaterians, including humans. It is homologous to the female ovary. The functions of the testes are to produce both sperm and androgens, primarily testoster ...

). In doing so, the Bidder's organ enlarges and produces viable

oocyte An oocyte (, ), oöcyte, or ovocyte 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 a female fetus in the ovary during female gametogenesis. The female ...

s (egg cells). Only rudimentary oviducts are developed, though, preventing eggs from actually being laid. The Bidder's organ only develops into an ovary analogue when testes are removed experimentally or not functioning properly (e.g. due to exposure to endocrine-disrupting chemicals). Importantly, females can have Bidder's organs in addition to true

ovaries The ovary is an organ in the female reproductive system that produces an ovum. When released, this travels down the fallopian tube into the uterus, where it may become fertilized by a sperm. There is an ovary () found on each side of the body. T ...

, which suggests that the Bidder's organ might not be a rudimentary ovary. It is named in honour of

Friedrich Bidder Georg Friedrich Karl Heinrich Bidder ( – ) was a Baltic German physiologist and anatomist from what was then the Governorate of Livonia in the Russian Empire. In 1834 he received his doctorate from the University of Dorpat, where he became a ...

Anatomy

The organ's internal anatomy consists of two parts; the central portion, consisting of

connective tissue Connective tissue is one of the four primary types of animal tissue, along with epithelial tissue, muscle tissue, and nervous tissue. It develops from the mesenchyme derived from the mesoderm the middle embryonic germ layer. Connective tiss ...

and rich in

blood vessel The blood vessels are the components of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away ...

s, and its periphery, consisting of the cortex, which contains follicles in various stages of development. Molecules of various

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

s are present in the outer layer of the follicles, homologous to the

zona pellucida The zona pellucida (plural zonae pellucidae, also egg coat or pellucid zone) is a specialized extracellular matrix that surrounds the plasma membrane of mammalian oocytes. It is a vital constitutive part of the oocyte. The zona pellucida first ...

of the

ovum The egg cell, or ovum (plural ova), is the female reproductive cell, or gamete, in most anisogamous organisms (organisms that reproduce sexually with a larger, female gamete and a smaller, male one). The term is used when the female gamete is ...

. The physiology of the Bidder's organ is unique, having no connection with

temperature-dependent sex determination Temperature-dependent sex determination (TSD) is a type of environmental sex determination in which the temperatures experienced during embryonic/larval development determine the sex of the offspring. It is only observed in reptiles and teleost fish ...

(i.e., reptiles, avians, and mammals).

Location in a dissected toad

The ideal specimen for dissection is ''Rhinella marina', the giant

cane toad The cane toad (''Rhinella marina''), also known as the giant neotropical toad or marine toad, is a large, terrestrial true toad native to South and mainland Central America, but which has been introduced to various islands throughout Oceania ...

. In the male toad, the Bidder's organ is beneath the

mesentery The mesentery is an organ that attaches the intestines to the posterior abdominal wall in humans and is formed by the double fold of peritoneum. It helps in storing fat and allowing blood vessels, lymphatics, and nerves to supply the intestines ...

of the intestine, between the two mesonephroi. It is a conspicuous organ, being colored red, and at the cranial poles of the large testes.

References

{{Reflist Toads Animal reproductive system