''Apistogramma agassizii'', commonly known as Agassiz's dwarf cichlid, is a species of

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 the Marañón and

Ucayali River The Ucayali River ( es, Río Ucayali, ) is the main headstream of the Amazon River. It rises about north of Lake Titicaca, in the Arequipa region of Peru and becomes the Amazon at the confluence of the Marañón close to Nauta city. The city of ...

in Peru, some tributaries of the

Amazon River The Amazon River (, ; es, Río Amazonas, pt, Rio Amazonas) in South America is the largest river by discharge volume of water in the world, and the disputed longest river system in the world in comparison to the Nile. The headwaters of t ...

, as well as downstream to the

estuary An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environment ...

in the Atlantic. It is named after the

Swiss-American Swiss Americans are Americans of Swiss descent. Swiss emigration to America predates the formation of the United States, notably in connection with the persecution of Anabaptism during the Swiss Reformation and the formation of the Amish commun ...

zoologist Zoology ()The pronunciation of zoology as is usually regarded as nonstandard, though it is not uncommon. is the branch of biology that studies the Animal, animal kingdom, including the anatomy, structure, embryology, evolution, Biological clas ...

and

geologist A geologist is a scientist who studies the solid, liquid, and gaseous matter that constitutes Earth and other terrestrial planets, as well as the processes that shape them. Geologists usually study geology, earth science, or geophysics, althou ...

Louis Agassiz Jean Louis Rodolphe Agassiz ( ; ) FRS (For) FRSE (May 28, 1807 – December 14, 1873) was a Swiss-born American biologist and geologist who is recognized as a scholar of Earth's natural history. Spending his early life in Switzerland, he rec ...

(1807-1873).

Description

''Apistogramma agassiziii'' is a small, sexual dimorphic, and territorial fish. The males are larger, more colorful, and have more prolonged fins compared to females of the species. Body color and fin length are important characteristics during courtship and mating in the breeding seasons where larger males are more likely to control better quality territory and have more access to food. The larger and more colorful males are preferred by buyers of ornamental fish. Both males and females undergo four developmental phases of gonad maturation: immature, developing, spawning capable, and regressing. Mature females release a single batch of

oocytes 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 ge ...

once in each breeding season. However spawning is partial - not all ''Apistogramma agassiziii'' spawn at the same time. This is possibly an evolutionary adaptation to extreme seasonal changes, i.e. changes in water level, that ensures the resilience of the species by continuously introducing new, young individuals into the population. The diet of ''Apistogramma agassiziii'' varies depending on habitat. In forest areas, the diet is mainly adult insects and insect fragments, whereas in a pasture environment, ''Apistogramma agassizii'' prefers the larvae of insects such as

Diptera Flies are insects of the order Diptera, the name being derived from the Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwings having evolved into advanced ...

species.

Distribution and habitat

''Apistogramma agassizii'' lives in shallow waters, endemic to the Amazon basin. It prefers habitats with minimal current where plant debris, particularly dead leaves, accumulate as shelter from predators, both larger fishes and aerial predators. Of the 94 species of ''Apistogramma'' considered valid, ''Apistogramma agassizii'', along with ''

Apistogramma cacatuoides ''Apistogramma cacatuoides'' or the cockatoo dwarf cichlid is a South American cichlid and the ''Apistogramma'' species most commonly bred in captivity. Characteristics The male cockatoo dwarf cichlid reaches a body length of 8 centimetres. Th ...

'' and '' Apistogramma bitaeniata'', is one of the very few with a large distribution range.

Taxonomy

Numerous researchers have suggested that the wide range suggests that ''Apistogramma agassizii'' is actually more than one distinct species. A study by Estivals et al. (2020) in the Peruvian Amazon showed at least three separate genotypic clusters and estimated that the ''Apistogramma agassizii'' designation actually holds "tens of species". Using molecular dating, they estimated that the three proposed species would have begun to diverge from the

most recent common ancestor In biology and genetic genealogy, the most recent common ancestor (MRCA), also known as the last common ancestor (LCA) or concestor, of a set of organisms is the most recent individual from which all the organisms of the set are descended. The ...

during the Plio-Pleistocene period, which greatly affected river dynamics and could have created geological restrictions between the different clusters, leading to species divergence. As a result, they propose that ''Apistogramma agassizii'' no longer be considered a single, widespread taxon, but rather a mosaic of species with distinct, but still unknown, geographical distribution.

Relationship to humans

In aquaria

Just like all

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 eco ...

s, ''Apistogramma agassizii'' requires weekly partial water changes in order to keep the

nitrate Nitrate is a polyatomic ion A polyatomic ion, also known as a molecular ion, is a covalent bonded set of two or more atoms, or of a metal complex, that can be considered to behave as a single unit and that has a net charge that is not zer ...

levels as low as possible. It prefers a hardness level of 50–100 mg/L and a pH of 6.0. They should be housed in an aquarium of at least 10 gallons. In order to reduce problems arising from their territorial nature, it is important to break up lines of sight within the aquarium, something that can be achieved with bogwood, root ornaments and hardy plants. They should not be kept in the same aquarium as other dwarf cichlids. A better choice of tankmates would be a shoal of tetras or other small fish native to the Amazon River.

Threats

''Apistogramma agassizii'' is affected by increasing water temperatures due to climate change. These effects can be exacerbated by

deforestation Deforestation or forest clearance is the removal of a forest or stand of trees from land that is then converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban use. The most concentrated d ...

, which affects the ability of ''Apistogramma agassizii'', other ''Apistogramma'' species, and other stream fishes to cope with changes in water temperature and quality. Additionally, fishermen along the Amazon have been known to use

barbasco Barbasco is the name of several plants that contain poisonous chemical compounds that have been used for fishing by indigenous populations of the Americas: * ''Lonchocarpus urucu'', used by Shuar and Nukak peoples as a poison for fishing. * ''Degue ...

, a plant-derived, non-specific

ichthyotoxin Ichthyotoxins are compounds which are either toxic to fish, or are toxins produced by fish. The former include the algae-produced euglenophycin and prymnesins, which can cause large-scale fish deaths. The latter includes ostracitoxin, produced by ...

that kills almost all fish in the area when used. ''Apistogramma agassizii'' is also highly sensitive to copper exposure, an increasing concern due to growing metal contamination in the Amazon.

Sources

* Encyclopaedia of Aquarium and Pond Fish (2005) (

David Alderton David Alderton is an English writer specialising in pets and natural history topics. Growing up in a home surrounded by pets, he originally trained to become a veterinary surgeon. An allergic dermatitis acquired in his final year of study forced ...

)

References

External links

*
Aggassizi Cichlid
in Animal-World {{Taxonbar, from=Q390808 agassizii Fish described in 1875 Taxa named by Franz Steindachner