Physogastrism or physogastry is a characteristic of certain arthropods (mostly insects and mites), where the abdomen is greatly enlarged and membranous. The most common examples are the "queens" of certain species of

eusocial Eusociality ( Greek 'good' and social) is the highest level of organization of sociality. It is defined by the following characteristics: cooperative brood care (including care of offspring from other individuals), overlapping generations wit ...

insects such as

termite Termites are a group of detritivore, detritophagous Eusociality, eusocial cockroaches which consume a variety of Detritus, decaying plant material, generally in the form of wood, Plant litter, leaf litter, and Humus, soil humus. They are dist ...

bee Bees are winged insects closely related to wasps and ants, known for their roles in pollination and, in the case of the best-known bee species, the western honey bee, for producing honey. Bees are a monophyletic lineage within the superfamil ...

s and

ant Ants are Eusociality, eusocial insects of the Family (biology), family Formicidae and, along with the related wasps and bees, belong to the Taxonomy (biology), order Hymenoptera. Ants evolved from Vespoidea, vespoid wasp ancestors in the Cre ...

s, in which the abdomen swells in order to hold enlarged

ovaries The ovary () is a gonad in the female reproductive system that produces ova; when released, an ovum travels through the fallopian tube/oviduct into the uterus. There is an ovary on the left and the right side of the body. The ovaries are endocr ...

, thus increasing

fecundity Fecundity is defined in two ways; in human demography, it is the potential for reproduction of a recorded population as opposed to a sole organism, while in population biology, it is considered similar to fertility, the capability to produc ...

. This means that the queen has the ability to hold more and produce more eggs at one time. Physogastric queens produce an enormous number of eggs which can account for a significant amount of their body weight. In the termite species ''

Macrotermes subhyalinus ''Macrotermes'' is a genus of termites belonging to the subfamily Macrotermitinae and widely distributed throughout Africa and South-East Asia. Well-studied species include ''Macrotermes natalensis'' and ''Macrotermes bellicosus, M. bellicosus.'' ...

'', eggs can make up a third of their body weight, and a 15-gram queen can produce up to 30 eggs per minute. The physogastric queens' egg production is supported by oocyte proteins supplied by the "queen body fat."

In termites

Physogastrism in

s presents itself in quite an unusual manner. Unlike most physogastric insects, the queen termite is able to increase its size without the use of cuticular molting. Rather, the queen unfolds and stretches her abdominal

epicuticle Arthropods are covered with a tough, resilient integument, cuticle or exoskeleton of chitin. Generally the exoskeleton will have thickened areas in which the chitin is reinforced or stiffened by materials such as minerals or hardened proteins. T ...

in order to make room for the subsequent egg deposits. This process has been observed to be incredibly slow (sometimes over the course of several years).

In bees

Many

stingless bee Stingless bees (SB), sometimes called stingless honey bees or simply meliponines, are a large group of bees (from about 462 to 552 described species), comprising the Tribe (biology), tribe Meliponini (or subtribe Meliponina according to other aut ...

species have physogastric queens, such as the South American species ''

Paratrigona subnuda ''Paratrigona subnuda'', commonly known as the jataí-da-terra ("ground jataí"), is a species of eusocial stingless bee in the family Apidae and tribe Meliponini. These social bees are prevalent in Neotropical moist forests, including Brazilian ...

'' and ''

Schwarziana quadripunctata ''Schwarziana quadripunctata'' is a small, stingless bee found in a stretch of the South American Amazon from Goiás, Brazil, through Paraguay, to Misiones, Argentina.Michener, C.D. (2007). ''The Bees of the World''. Baltimore: Johns Hopkins Univ ...

''. Physogastrism can also be seen in the stingless bee species ''

Melipona bicolor ''Melipona bicolor'' , commonly known as Guaraipo or Guarupu, is a Eusociality, eusocial bee found primarily in South America. It is an inhabitant of the Araucaria moist forests, Araucaria Forest and the Atlantic Rainforest, and is most commonly ...

'', which is facultatively

polygynous Polygyny () is a form of polygamy entailing the marriage of a man to several women. The term polygyny is from Neoclassical Greek πολυγυνία (); . Incidence Polygyny is more widespread in Africa than in any other continent. Some scholar ...

, and therefore one or more physogastric queens can be found in the same colony.Koedam, D., et al. "The behaviour of laying workers and the morphology and viability of their eggs In ''Melipona bicolor bicolor''." Physiological Entomology 26.3 (2001): 254-259. Academic Search Premier. Web. 26 Sept. 2015. These queens interact with each other within the colony, and during the patrolling phase, a queen may attempt to touch the

abdomen The abdomen (colloquially called the gut, belly, tummy, midriff, tucky, or stomach) is the front part of the torso between the thorax (chest) and pelvis in humans and in other vertebrates. The area occupied by the abdomen is called the abdominal ...

of another queen. The other queen turns her abdomen away, and what follows is the two queens circling one another, trying to touch the other's abdomen; as such, the queens are almost always active.Hayo H.W. Velthuis, Han De Vries, Vera L. Imperatriz-Fonseca. The polygyny of ''Melipona bicolor'': scramble competition among queens. Apidologie, Springer Verlag (Germany), 2006, 37 (2), pp.222-239.

In non-social insects and other arthropods

Various lineages of non-social insects demonstrate various degrees of physogastry, especially among females. The most dramatic and best-known are among the

beetle Beetles are insects that form the Taxonomic rank, order Coleoptera (), in the superorder Holometabola. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 40 ...

s, especially certain groups that live inside ant or termite nests, where the distended abdomen is thought to enhance integration into their hosts' colonies, though it is also seen in several herbivorous beetle lineages such as

Chrysomelidae The beetle family Chrysomelidae, commonly known as leaf beetles, includes over 37,000 (and probably at least 50,000) species in more than 2,500 genera, making it one of the largest and most commonly encountered of all beetle families. Numerous s ...

(e.g., ''

Gastrophysa ''Gastrophysa'' is a genus of beetles in the family Chrysomelidae, in which the females typically exhibit swollen, membranous abdomens, a condition known as physogastrism. Species These nine species belong to the genus ''Gastrophysa'': * '' Ga ...

'') and

Meloidae Blister beetles are beetles of the family Meloidae, so called for their defensive secretion of a blistering agent, cantharidin. About 7,500 species are known worldwide. Many are conspicuous and some are aposematically colored, announcing their ...

(e.g., ''

Megetra ''Megetra'' is a genus of blister beetles in the family Meloidae Blister beetles are beetles of the family Meloidae, so called for their defensive secretion of a blistering agent, cantharidin. About 7,500 species are known worldwide. Many are ...

''). Females of

endoparasitic Parasitism is a close relationship between species, where one organism, the parasite, lives (at least some of the time) on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The ent ...

fleas, in particular in the genus '' Tunga'', exhibit severe physogastry once they have penetrated the host's skin and begun to produce eggs. Many

Acari Mites are small arachnids (eight-legged arthropods) of two large orders, the Acariformes and the Parasitiformes, which were historically grouped together in the subclass Acari. However, most recent genetic analyses do not recover the two as ea ...

(ticks and mites) have physogastric females, sometimes involving precocious development of offspring inside the mother's body.

References

{{reflist Arthropod anatomy

In termites

In bees

In non-social insects and other arthropods

See also

References