The parotoid gland (alternatively, paratoid gland) is an external skin gland on the back, neck, and shoulder of

toad Toad is a common name for certain frogs, especially of the family Bufonidae, that are characterized by dry, leathery skin, short legs, and large bumps covering the parotoid glands. A distinction between frogs and toads is not made in scient ...

s and some

frog A frog is any member of a diverse and largely carnivorous group of short-bodied, tailless amphibians composing the order Anura (ανοὐρά, literally ''without tail'' in Ancient Greek). The oldest fossil "proto-frog" ''Triadobatrachus'' is ...

s and

salamander Salamanders are a group of amphibians typically characterized by their lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults. All t ...

s. It can secrete a number of milky

alkaloid Alkaloids are a class of basic, naturally occurring organic compounds that contain at least one nitrogen atom. This group also includes some related compounds with neutral and even weakly acidic properties. Some synthetic compounds of similar ...

substances (depending on the species) known collectively as

bufotoxins Bufotoxins are a family of toxic steroid lactones or substituted tryptamines of which some may or may not be toxic. They occur in the parotoid glands, skin, and poison of many toads (genus ''Bufo'') and other amphibians, and in some plants and mu ...

, which act as

neurotoxins Neurotoxins are toxins that are destructive to nerve tissue (causing neurotoxicity). Neurotoxins are an extensive class of exogenous chemical neurological insultsSpencer 2000 that can adversely affect function in both developing and mature nerv ...

to deter

predation Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...

. These cutaneous glands are called parotoid as they are somewhat similarly positioned to mammalian

parotid gland The parotid gland is a major salivary gland in many animals. In humans, the two parotid glands are present on either side of the mouth and in front of both ears. They are the largest of the salivary glands. Each parotid is wrapped around the ma ...

, although the latter have a different function, excreting saliva within the mouth rather than externally excreted defensive chemicals. A study of the parotoid glands of the

Colorado River toad The Colorado River toad (''Incilius alvarius''), formerly known as the Sonoran Desert toad, is found in northern Mexico and the southwestern United States. It exudes toxins from glands within its skin that have psychoactive properties. Descript ...

in 1976 found that the parotoid glands were "composed of numerous lobules", each of which is a separate unit with a lumen surrounded by a double cell layer. The cell layers have interlocking microvilli. The study found that the outer cell layer resembled smooth muscle cells, with some organelles hypothesised to "function in some aspects of venom synthesis, active cellular transport and contraction in the discharge of the secretory product". The inner layer was hypothesised to be "involved in venom formation and release". The study noted that the structure of the parotoid glands of the Colorado River toad is very different from the structure of the same glands in the

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 ...

. There is extensive blood supply to the parotoid glands to deliver

cholesterol Cholesterol is any of a class of certain organic molecules called lipids. It is a sterol (or modified steroid), a type of lipid. Cholesterol is biosynthesized by all animal cells and is an essential structural component of animal cell mem ...

and other toxin precursor chemicals to the gland. Parotoid glands are sometimes said to be

wart Warts are typically small, rough, hard growths that are similar in color to the rest of the skin. They typically do not result in other symptoms, except when on the bottom of the feet, where they may be painful. While they usually occur on the ...

-like in appearance, though warts are abnormal growths caused by viral infections while parotoid glands are normal, healthy parts of the animals that bear them. The vague similarity in appearance, however, is the reason behind the mistaken belief that touching a toad causes warts.

Notes

{{reflist Vertebrate anatomy Amphibians

See also

Notes