Hoplosternum littorale is a species of catfish (order Siluriformes) belonging to the Callichthyinae subfamily of the family Callichthyidae.

[1][3] It is not found in rainforest creeks and clearwater rivers draining Precambrian Guyana and Brazilian Shields, where water is extremely poor in dissolved minerals.

This species is restricted to swamps of tropical and subtropical South America and the floodplains of Amazonian whitewater rivers originating in the Andes.

Such environments are characterized by low levels of dissolved oxygen and markedly seasonal conditions caused primarily by fluctuations in rainfall.

Newly hatched larvae do not have the ability to breathe air through their intestines; however, it is possible that they absorb oxygen through their skin at this point, before the armor plates have developed.

Soon after, between about 12–23 days of age, young have the capacity to breathe air, but their respiratory intestine has not finished developing.

In H. littorale, cathodic hemoglobin has a pronounced reversed Bohr effect in which oxygen affinity increases with decreased pH.

Cathodic hemoglobin has the purpose of safeguarding oxygen transport to tissues under hypoxic and acidotic conditions.

Immature fish feed primarily on small aquatic crustaceans, especially Cladocera, Ostracoda, Copepoda, and Eubranchipoda.

[6] This dome-shaped nest is rich with oxygen; in the hypoxic water conditions of tropical swamps, the main function of the bubble nest appears to be to provide oxygen to the developing eggs by lifting the eggs above the water surface while protecting them from desiccation.

It may also serve to protect the brood against predators, regulate temperature, identify the center of the male's territory, and to synchronize reproductive activities.

Despite intense predation pressure on eggs and larvae, the male's guarding behavior extends for only one or two days after hatching.

[1] The male attacks with its large pectoral spines erect; the attack consists of rapid propulsion towards its target followed by a sharp lateral turn, which causes the rough outer edge of pectoral spine to drag across the target and cause abrasion.

[1] In Guyana, French Guiana, Suriname, and Trinidad, this species is an extremely popular food fish.