Agassiz's dwarf cichlid
Apistogramma agassizii, commonly known as Agassiz's dwarf cichlid, is a species of cichlid found in the Marañón and Ucayali River in Peru, some tributaries of the Amazon River, as well as downstream to the estuary in the Atlantic. It is named after the Swiss-American zoologist and geologist Louis Agassiz (1807-1873).
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 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 species.
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 and Apistogramma bitaeniata, is one of the very few with a large distribution range.
Apistogramma agassizii is affected by increasing water temperatures due to climate change. These effects can be exacerbated by deforestation, 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, a plant-derived, non-specific ichthyotoxin 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.
