The bronze corydoras (Osteogaster aenea), also known as the green corydoras, bronze catfish, lightspot corydoras or wavy catfish, is a species of freshwater fish in the armored catfish family, Callichthyidae, often kept as an aquarium fish. It is widely distributed in South America on the eastern side of the Andes, from Colombia and Trinidad to the Río de la Plata basin; It was originally described as Hoplosoma aeneum (based on a specimen from Trinidad) by Theodore Gill in 1858 and has historically also been referred to as Corydoras aeneus.
Appearance and anatomy
The adult size is 6½ cm for males and a slightly larger 7 cm for females (2½ to 2¾ inches). Females have a slightly higher body frame than males in accordance with their larger abdominal region. Their average life span is 10 years. It has a yellow or pink body, white belly, and is blue-grey over its head and back. Its fins are yellow or pink and immaculate. In common with most Corydoradini the dorsal, pectoral and adipose fins have an additional sharp barb and have a mild poison which causes fish which try to attack them to get stung. A brownish-orange patch is usually present on the head, just before the dorsal fin, and is its most distinctive feature when viewed from above in the stream. Their upper sides are often a greenish color, which is the reason another common name for this fish is the green cory.
Ecology
They are found in quiet, shallow waters with soft bottoms that can sometimes be heavily polluted by clouds of disturbed mud from the bottom, but it also inhabits running waters.
In laboratory observations, it was found that bronze corydoras have a unique method of insemination. When these fish reproduce, the male will present his abdomen to the female. The female will attach her mouth to the male's genital opening, creating the well-known "T-position" many Corydoras exhibit during courtship. The female will then drink the sperm. The sperm rapidly moves through her intestines and is discharged together with her eggs into a pouch formed by her pelvic fins. The female can then swim away and deposit the pouch somewhere else alone. Because the T-position is exhibited in other species than just O. aenea, it is likely that they also exhibit this behavior. In the wild, eggs are laid on waterweeds.
In the aquarium
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Bronze corydoras are likely the most popular Corydoradini species. It is annually bred and shipped in large quantities all over the world. It is easily bred and is produced in commercial quantities in the United States, Europe, and Singapore. Most of the available fish are therefore captive-bred strains. Wild imports are reported to be less easy to breed.
They are a hardy and useful aquarium fish despite having a coloration that is by no means striking or unusual. Many aquarists are fascinated by the habits of these fish. They ceaselessly comb the bottom of the aquarium for food and therefore disturb it slightly, sending up detritus and waste material that has settled loosely on the bottom. They prefer being kept in groups of 5 or more, being sociable fish and are ideal fish for a community tank. Others say that the albinos are practically blind and that the males are somewhat sterile, although this may be due to extensive inbreeding.