Corydoras agassizii

Corydoras: from the Ancient Greek κόρυς (korus), meaning 'helmet', and δορά (dora), meaning 'skin, hide of an animal', in allusion to the rows of bony plates on the flanks of genus members.

agassizii: named for Dr. J. Louis R. Agassiz.

Type locality is 'Amazon River near Tabatinga, Amazonas, Brazil'. Tabatinga is a municipality in the Três Fronteiras region where the borders of Brazil, Peru, and Colombia meet, but this species' wider distribution is unclear.

Records exist from the Río Nanay, more than 200 kilometres upstream of the type locality, so it appears to range at least as far as the city of Iquitos in Loreto Regio, Peru, but distribution is usually given as 'Amazon River basin near border of Brazil and Peru'.

Ideally use a substrate of fine sand, although rounded gravel is an acceptable alternative provided it's kept scrupulously clean.

Other décor is largely down to personal choice, but some cover should be provided to give the fish security.

Corydoras spp. are foraging omnivores and will accept most sinking dried foods, as well as small live and frozen varieties such as bloodworm, Tubifex, etc.

Feeding a varied diet will ensure the fish are in optimum condition.

Under no circumstances should they be expected to survive on 'left-overs' from other inhabitants of the aquarium or relied on to 'clean' the aquarium.

Peaceful and gregarious. Should be maintained in a group of at least 4-6 individuals.

Females tend to grow larger, and sexually mature individuals are noticeably rounder and broader-bodied than males, especially when gravid.

This species' name is commonly misapplied to a number of similar-looking fishes and it can be difficult to identify even if collection locality is known.

Colour pattern is variable, for example, and it's not clear whether this occurs between, within, or both between and within populations.

In the original description, Steindachner did note that the first three dorsal-fin rays are completely black while the remainder is whitish with rows of small, brownish spots. Some specimens had a larger brownish spot at the upper edge of the same fin.

In addition, the ventral fins were described as unmarked and yellowish, the pelvic fins also yellowish with the first ray brownish, and the caudal-fin bluish-white with 3-5 regular rows of transverse brown spots. A blurred 'yellowish' stripe runs along the lateral line.

The species with which C. agassizii is most often confused is C. ambiacus Cope, 1872, with its colour pattern described as follows: straw-coloured with numerous indefinite brown spots on the sides. Dorsal-fin with a large black spot covering anterior half, which also expands on the dorsal region around the base of the fin. Four vertical brown bands on caudal-fin, anal spotted. Cheeks with blue reflections.'

Fish with variable colour patterns but more-or-less matching both these descriptions are widely-available in the aquarium trade, although the latter seem far more common than the former.

The fact that Steindachner did not mention the presence of any black markings on the upper body in his description of C. agassizii may also be significant.

The genus Corydoras is among the largest catfish groups and currently contains over 150 valid species.

It is included in the family Callichthyidae, of which members are often referred to collectively as 'armoured' or 'mailed' catfishes group due to the presence of bony plates in place of scales on the body.

Their taxonomy can be confusing, and numerous undescribed species are also thought to exist.

Fish of unconfirmed identification entering the aquarium hobby are therefore typically assigned a 'C' or 'CW' number for purposes of reference and organisation.

They are facultative air breathers and possess a modified, highly vascularised intestine which has evolved to facilitate uptake of atmospheric oxygen and aid survival in oxygen-deprived environments. In the aquarium you'll occasionally see them rising to the surface to take in gulps of air.

The stiffened pectoral-fin spines are capable of piercing human skin and a 'sting' can be very painful indeed, so care should be exercised when handling them.

It is thought that secretions from the axillary glands at the base of each spine may even be mildly toxic or venomous.