A gamergate ( ) is a mated
worker ant
Ants are eusocial insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from vespoid wasp ancestors in the Cretaceous period. More than 13,800 of an estimated total of 22,0 ...
that can reproduce sexually, i.e., lay fertilized eggs that will develop as females. In the vast majority of ant species, workers are sterile and gamergates are restricted to taxa where the workers have a functional sperm reservoir ('
spermatheca'). In some species, gamergates reproduce in addition to winged queens (usually upon the death of the original foundress), while in other species the queen caste has been completely replaced by gamergates. In gamergate species, all workers in a colony have similar reproductive potentials, but as a result of physical interactions, a dominance hierarchy is formed and only one or a few top-ranking workers can mate (usually with foreign males) and produce eggs. Subsequently however, aggression is no longer needed as gamergates secrete chemical signals that inform the other workers of their reproductive status in the colony.
Depending on the species, there can be one gamergate per colony (
monogyny) or several gamergates (
polygyny
Polygyny (; from Neoclassical Greek πολυγυνία (); ) is the most common and accepted form of polygamy around the world, entailing the marriage of a man with several women.
Incidence
Polygyny is more widespread in Africa than in any ...
). Most gamergate species have colonies with a few hundred or fewer workers.
Etymology
"Gamergate" derives from the Greek words (''gámos'') and (''ergátēs'') and means "married worker". It was coined in 1983 by geneticist
William Louis Brown[ and was first used in scientific literature by entomologists Christian Peeters and Robin Crewe in a 1984 paper published in '']Naturwissenschaften
''The Science of Nature'', formerly ''Naturwissenschaften'', is a monthly peer-reviewed scientific journal published by Springer Science+Business Media covering all aspects of the natural sciences relating to questions of biological significance. I ...
''.[ The definition typically found in entomological dictionaries is "mated, egg-laying worker",][ and is drawn from the glossary of Bert Hölldobler and E. O. Wilson's 1990 book, '']The Ants
''The Ants'' is a zoology textbook by the German entomologist Bert Hölldobler and the American entomologist E. O. Wilson, first published in 1990. It won the Pulitzer Prize for General Non-Fiction in 1991.
Contents
This book is primarily aimed a ...
''.[
]
Description
There are 100–200 different species in which gamergates reproduce (roughly 1% of all ants), most of which fall within the poneromorph subfamilies. Whereas workers (which are all females) in most ant species are morphologically incapable of storing sperm, in gamergate species one or several workers mate and have active 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 ...
.[ Gamergate lifespan is short compared to queens in queenright colonies, but gamergates can be replaced by other dominant workers in the colony without risking colony survival. Reproductive investment in gamergate females is thus optimized because non-differentiated gamergates (i.e. reproductively inactive workers) function as laborers.][
]
Caste structure
Within gamergate colonies, all workers are born reproductively viable and are thus potential gamergates. Prior to differentiation as a gamergate, a dominant worker must physically inhibit its sisters. For example, in the case of '' Diacamma australe'', the first female to become reproductively active will clip off the thoracic
The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the crea ...
gemmae of her sisters, thus greatly reducing their sexual attractiveness. In other genera, persistent domination of worker females by gamergates via physical aggression all but ensure that they will not produce male offspring.[ In '' Diacamma nilgiri'', gamergates use dominance interactions to monopolize reproduction without mutilation of sister workers.][ The same is true for '']Streblognathus peetersi
''Streblognathus'' is a genus of ants in the subfamily Ponerinae. The genus contains two species found in southern Africa.
Species
* ''Streblognathus aethiopicus'' (Smith, 1858)
* '' Streblognathus peetersi'' Robertson, 2002
Biology
Both speci ...
'', which engage in non-injurious aggression to determine dominance.[ For most gamergate species, the start of ovarian activity eliminates the need to physically dominate nestmate workers. Instead newly produced ]pheromone
A pheromone () is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to affect the behavio ...
s or signaling chemicals ensure that workers remain nonreproductive. Although it is unknown to what degree these chemicals act as pheromones or as signals, support for the signaling hypothesis can be found in the loss of reproductive inhibition of workers as the gamergate grows older and her 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 natural capability to pr ...
diminishes.[
Mechanisms of gamergate replacement vary among monogynous and polygynous species. When a gamergate dies, it is usually replaced by a formerly submissive worker who proceeds to mate and begins ovarian activity. A new gamergate often originates from a younger ]cohort
Cohort or cohortes may refer to:
* Cohort (educational group), a group of students working together through the same academic curriculum
* Cohort (floating point), a set of different encodings of the same numerical value
* Cohort (military unit) ...
. For example, when the original founding queen dies in a ''Harpegnathos saltator
''Harpegnathos saltator'', sometimes called the Indian jumping ant or Jerdon's jumping ant, is a species of ant found in India. They have long mandibles and have the ability to leap a few inches. They are large-eyed and active predators that ...
'' colony, younger workers begin to fight for dominance and some become the next reproductives.[ Because reproductively inactive workers are able to activate their ovaries after the death of the gamergate, some gamergate species can be considered cooperative breeders rather than truly ]eusocial insect
Eusociality (from Greek εὖ ''eu'' "good" and social), the highest level of organization of sociality, is defined by the following characteristics: cooperative brood care (including care of offspring from other individuals), overlapping generat ...
s.[
In colonies with both queens and gamergates, the latter function as secondary reproductives.][ Research on Amblyoponinae species has shown that there is a fecundity-based hierarchy among gamergates. In '' Stigmatomma reclinatum'', it was found that higher-ranked gamergates had more fully developed ]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 than low-ranked gamergates.[ In ''Streblognathus peetersi,'' only the alpha worker mates and becomes the gamergate; younger workers await a chance to reproduce when the current gamergate exhibits decreased fecundity or dies.][ Challenges to gamergates from subordinate workers are risky because the gamergate in species like '' Dinoponera quadriceps'' may mark the challenger by rubbing special chemicals produced only by the gamergate. These chemicals signal to other workers to immobilize the challenger by biting her appendages and immobilizing her for a few days until her ]hormonal
A hormone (from the Greek participle , "setting in motion") is a class of signaling molecules in multicellular organisms that are sent to distant organs by complex biological processes to regulate physiology and behavior. Hormones are required f ...
levels return to normal.[ Subordinate workers play an important policing role in the selection of future gamergates and are thus able to increase their indirect fitness.][
]
Social structure variation and ecology
There is much variation in the social structure of ant colonies with gamergates. Some species such as ''Harpegnathos saltator
''Harpegnathos saltator'', sometimes called the Indian jumping ant or Jerdon's jumping ant, is a species of ant found in India. They have long mandibles and have the ability to leap a few inches. They are large-eyed and active predators that ...
'',[ '' Pseudoneoponera tridentata'', '' Gnamptogenys menadensis'', and '' Rhytidoponera confusa'' have a winged alate queen caste as well as gamergates.][ Queenless species with only gamergates and workers may have a ]monogynous
This is a glossary of terms used in the descriptions of ants.
A
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See also
...
structure with a single gamergate or they may have a polygynous
Polygyny (; from Neoclassical Greek πολυγυνία (); ) is the most common and accepted form of polygamy around the world, entailing the marriage of a man with several women.
Incidence
Polygyny is more widespread in Africa than in any ...
structure with multiple gamergates. Examples of monogynous queenless species include '' Pachycondyla krugeri'', '' P. sublaevis'', ''Diacamma australe'', '' D. rugosum'', '' Dinoponera quadriceps'', '' Platythyrea lamellosa'', and ''Streblognathus aethiopicus
''Streblognathus'' is a genus of ants in the subfamily Ponerinae. The genus contains two species found in southern Africa.
Species
* '' Streblognathus aethiopicus'' (Smith, 1858)
* '' Streblognathus peetersi'' Robertson, 2002
Biology
Both spec ...
''.[ Examples of polygynous queenless species include '']Ophthalmopone berthoudi
''Ophthalmopone'' is a ponerine genus of ants found in Sub-Saharan Africa. Workers are slender and large in size (8–13.5 mm). Queens seem to be absent, but gamergates (reproductive female workers) present.
Species
*'' Ophthalmopone b ...
'', '' O. hottentota'', and all known queenless species of '' Rhytidoponera''.[ In the queenless ''Ophthalmopone berthoudi'', foreign males visit underground nests to mate with young workers.][
Ecologically, gamergate species from different ]tribes
The term tribe is used in many different contexts to refer to a category of human social group. The predominant worldwide usage of the term in English is in the discipline of anthropology. This definition is contested, in part due to confli ...
and genera
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclat ...
often tend to share certain characteristics. Many gamergate species are solitary generalist foragers living in arid
A region is arid when it severely lacks available water, to the extent of hindering or preventing the growth and development of plant and animal life. Regions with arid climates tend to lack vegetation and are called xeric or desertic. Most ...
environments. Similar to species with ergatoid
An ergatoid (from Greek '' ergat-'', "worker" + ''-oid'', "like") is a permanently wingless reproductive adult ant or termite. The similar but somewhat ambiguous term ergatogyne refers to any intermediate form between workers and standard gynes. ...
queens, the evolution of gamergate reproduction is hypothesized to be associated with a shift to colonial fission. Myrmecologists Christian Peeters and Fuminori Ito have also suggested that "the evolution of gamergate reproduction appears strongly associated with the adaptive benefits of secondary polygyny (e.g. increased colony lifespan and resource inheritance), and it is the preferred option in species having workers able to store sperm."
Classification dispute
The utility of "gamergate" as a morphological designation is not without critics. Within the field of myrmecology
Myrmecology (; from Greek: wikt:μύρμηξ, μύρμηξ, ''myrmex'', "ant" and λόγος, ''logos'', "study") is a branch of entomology focusing on the science, scientific study of ants. Some early myrmecologists considered ant society as th ...
it is a matter of dispute whether caste
Caste is a form of social stratification characterised by endogamy, hereditary transmission of a style of life which often includes an occupation, ritual status in a hierarchy, and customary social interaction and exclusion based on cultur ...
should be defined primarily by reproductive role or by physical morphology. Notably, Alfred Buschinger has argued that the term "worker" should be applied only to those ants who make up the non-reproductive caste and "queen" should be applied only to reproductively viable female ants regardless of their physical appearance. Hölldobler and Wilson suggest that the two positions can be semantically resolved and that the most fruitful approach would be to keep classification "somewhat loose, incorporating either anatomy or roles in a manner that maximizes convenience, precision, and clarity of expression."[
]
Genera with gamergates
This list may be incomplete and may require expansion:
* Poneromorph subfamilies
** Amblyoponinae
***'' Stigmatomma''[Throughout Ito's 1993 paper for the ''Journal of Natural History'', he refers not to ''Stigmatomma'' but to ''Amblyopone''. At the time ''Stigmatomma'' was considered to be a synonym of ''Amblyopone''.]
**Ectatomminae
Ectatomminae is a subfamily of ant
Ants are eusocial insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from vespoid wasp ancestors in the Cretaceous period. More t ...
***'' Gnamptogenys''[
***'' Rhytidoponera''][
**]Ponerinae
Ponerinae is a subfamily of ants in the Poneromorph subfamilies group, with about 1,600 species in 47 extant genera, including '' Dinoponera gigantea'' - one of the world's largest species of ant. Mated workers have replaced the queen as the ...
***'' Bothroponera''
***'' Diacamma''[
***'' Dinoponera''][
***'']Euponera
''Euponera'' is a ponerine genus of ants distributed in the Afrotropics (including Madagascar
Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de ...
''
***''Hagensia
''Hagensia'' is a small genus of ants in the subfamily Ponerinae. Its two species are known only from coastal areas in South Africa. Workers are large (10.5–13.0 mm); queens
Queens is a borough of New York City, coextensive with Quee ...
''
***''Harpegnathos
''Harpegnathos'' is a small ponerine genus of ants found in South and Southeast Asia. They are notable for their jumping ability, complex colony structure, and large to very large workers easily identifiable by their long mandibles and large eyes ...
''[
***'']Leptogenys
''Leptogenys'' is a genus of ants in the subfamily Ponerinae. ''Leptogenys'' is the most diverse ponerine ant genus in the world; it is widespread throughout tropical and subtropical regions and there are over 260 extant species described. Most ...
''
***''Ophthalmopone
''Ophthalmopone'' is a ponerine genus of ants found in Sub-Saharan Africa
Sub-Saharan Africa is, geographically, the area and regions of the continent of Africa that lies south of the Sahara. These include West Africa, East Africa, Cent ...
''[
***'']Platythyrea
''Platythyrea'' is a genus of predaceous ants in the subfamily Ponerinae and the sole member of the tribe Platythyreini.
Distribution
The genus has a worldwide distribution, and is found in the tropics and subtropics of the world.
Descript ...
''[
***'' Pseudoneoponera'']
***''Streblognathus
''Streblognathus'' is a genus of ants in the subfamily Ponerinae. The genus contains two species found in southern Africa.
Species
* '' Streblognathus aethiopicus'' (Smith, 1858)
* '' Streblognathus peetersi'' Robertson, 2002
Biology
Both spec ...
''[
***'' Thaumatomyrmex'']
*Myrmeciinae
Myrmeciinae is a subfamily of the Formicidae, ants once found worldwide but now restricted to Australia and New Caledonia. This subfamily is one of several ant subfamilies which possess gamergates, female worker ants which are able to mate an ...
::*'' Myrmecia''[
*]Myrmicinae
Myrmicinae is a subfamily of ants, with about 140 extant genera; their distribution is cosmopolitan. The pupae lack cocoons. Some species retain a functional sting. The petioles of Myrmicinae consist of two nodes. The nests are permanent and ...
::*'' Metapone''[
]
See also
* Laying worker bee
* Mermithergate
A mermithergate is an ant worker that has a changed appearance as a result of an Enoplia nematode infection.
Etymology
The word was coined by William M. Wheeler in 1910. It is a combination of the nematode genus ''Mermis'', for which Wheeler ...
* Parthenogenetic reproduction in insects
* Worker policing
Worker policing is a behavior seen in colonies of social hymenopterans (ants, bees, and wasps) whereby worker females eat or remove eggs that have been laid by other workers rather than those laid by a queen. Worker policing ensures that the o ...
Notes
References
{{Eusociality
Ants
Insect reproduction