The goldeneye cichlid (''Nannacara anomala'') is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

cichlid Cichlids are fish from the family Cichlidae in the order Cichliformes. Cichlids were traditionally classed in a suborder, the Labroidei, along with the wrasses ( Labridae), in the order Perciformes, but molecular studies have contradicted this ...

found in fresh water from the Aruka River in

Guyana Guyana ( or ), officially the Cooperative Republic of Guyana, is a country on the northern mainland of South America. Guyana is an indigenous word which means "Land of Many Waters". The capital city is Georgetown. Guyana is bordered by the ...

, to the

Maroni River The Maroni or Marowijne (french: link=no, Maroni, nl, Marowijne, Sranan Tongo: ''Marwina-Liba'') is a river in South America that forms the border between French Guiana and Suriname. Course The Maroni runs through the Guianan moist forest ...

Suriname Suriname (; srn, Sranankondre or ), officially the Republic of Suriname ( nl, Republiek Suriname , srn, Ripolik fu Sranan), is a country on the northeastern Atlantic coast of South America. It is bordered by the Atlantic Ocean to the north ...

. It is often found on flooded

savanna A savanna or savannah is a mixed woodland-grassland (i.e. grassy woodland) ecosystem characterised by the trees being sufficiently widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach the ground to ...

s near the coast. The male grows to a length of about while the female is somewhat smaller, and is thus regarded as a

dwarf cichlid Dwarf cichlid is a term used by fishkeeping hobbyists to describe an arbitrary assemblage of small-sized fish from the family Cichlidae. Although the grouping is widely used in the aquarium industry and hobby, the grouping has no taxonomic or ...

. The male, under acidic conditions, adopts a greenish tinge along the length of its body, while the female puts on a black coat with a faint line running from her face to the middle of her tail, and in breeding condition, fades into a bright yellow in the stomach. As youngsters, there is hardly any difference as a juvenile male does have the colouration of a female. The only difference would be the presence of an extension at the back of the male's dorsal fin. The goldeneye cichlid lives on a diet of

crustacean Crustaceans (Crustacea, ) form a large, diverse arthropod taxon which includes such animals as decapods, seed shrimp, branchiopods, fish lice, krill, remipedes, isopods, barnacles, copepods, amphipods and mantis shrimp. The crustacean group ...

insect Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three pairs ...

s, and other small animals.

Signaling and communication between competing males

cichlids Cichlids are fish from the family (biology), family Cichlidae in the order Cichliformes. Cichlids were traditionally classed in a suborder, the Labroidei, along with the wrasses (Labridae), in the order Perciformes, but molecular studies have c ...

, males are larger and more colorful than females, and have elongated fins. These physical differences allow for signaling between males as they compete with each other for females that are ready to

spawn Spawn or spawning may refer to: * Spawn (biology), the eggs and sperm of aquatic animals Arts, entertainment, and media * Spawn (character), a fictional character in the comic series of the same name and in the associated franchise ** '' Spawn: ...

. Through a specific sequence of displays, males communicate their fighting ability to each other, which allows opponents to assess whether the fight is worthwhile. The specific order of displays follows a consistent pattern: # Contestants will orient laterally and erect their fins. # They beat their tails and push a stream of water at their opponents, taking turns to display and receive the stream. # The males begin to face each other and biting increases. # Contestants engage in mouth wrestling in which they will grip each other's jaws and push and pull in order to determine the other's strength. # Both fish end up swimming quickly in tight circles, each trying to bite the others’ backs. # Finally, the losing fish will signal its surrender by folding its fins and changing its color as it retreats. Sequential assessment game models show that an individual's decision to give up will be based on its fighting ability. Competitions between individuals of similar size will proceed to the later phases of the behavioral sequence, while those contests with a large size asymmetry should be expected to end earlier in the sequence. Thus, fights may end at different phases along in the sequence, with short fights only involving low-intensity behaviors. As fights escalate, the risk to the opponents increases, as later phases in the display process involve more dangerous behavioral elements. The fish cooperate in behaviors such as tail beating and mouth wrestling in order to properly assess the relative fighting ability of opponents. This cooperative behavior allows for a form of communication between contesting fish, possibly as a means of decreasing the possibility for escalation.

Coloration and visual assessment

Cichlids may use coloration as a means of transmitting information to opponents in order to signal cooperative behaviors. The ability to display color is not indicative of size or fighting ability, and is an option available to all individuals. Color displays can indicate an aggressive state in cichlids, but can also be used to signal specific agonistic behaviors within a fight, such as a display of medial lines indicating tail-beating behavior. Coordinating displays, which are facilitated by coloration as a signal, may decrease the costs of fighting for both individuals by avoiding fight escalation. Visual assessment of ability also plays a role during male cichlid fights, although precision is quite low. Visual assessment can only be made when there is a large discrepancy between the sizes of competing individuals.

Presence of a predator

It is possible to see changes in the way competing cichlids

communicate Communication (from la, communicare, meaning "to share" or "to be in relation with") is usually defined as the transmission of information. The term may also refer to the message communicated through such transmissions or the field of inquir ...

with one another when they are in the presence of a predator. In highly escalated behaviors such as mouth wrestling,

vigilance Vigilance may refer to: * Alertness * Vigilance, a creature ability in the ''Magic: The Gathering'' collectible card game * ''Vigilance'' (album), by Threat Signal * Vigilance (behavioural ecology), the watchfulness of prey for nearby predator ...

is greatly reduced. In the presence of a predator, opponents may prefer to engage in low-intensity behaviors, such as lateral display and tail beating, even after the fight has escalated. This allows the individuals to maintain a higher level of vigilance while attempting to reduce the overall danger to themselves.

References

{{Taxonbar, from=Q3666 Goldeneye cichlid Fish of South America Fish described in 1905