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Corydoras ambiacus COPE, 1872

SynonymsTop ↑

Corydoras grafi Holly, 1940; Corydoras longirostris Hoedeman 1952


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.

ambiacus: named for the ‘Ambiyacu’, now commonly-referred to as ‘Ampiyacu’ River, type locality of the species.


Order: Siluriformes Family: Callichthyidae


Described from the Río Ampiyacu, a small tributary draining into the main Amazon channel in Loreto Department, northeastern Peru, with additional records from the Yavarí (Javari), Napo, Nanay, and lower Ucayali drainage basins.

All of these are Amazon tributaries, and C. ambiacus appears to occur in most or all affluents of the main Amazon channel between the ‘Três Fronteiras’ area where the borders of Brazil, Peru, and Colombia meet and the Río Ucayali, which enters the Amazon south of Iquitos, Peru.

In the Napo basin it’s also been collected from the Pangayacu and Yasuni tributary systems, Ecuador.

Maximum Standard Length

60 – 65 mm.


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.

Water Conditions

Temperature21 – 27 °C

pH6.0 – 8.0

Hardness36 – 215 ppm


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

Behaviour and CompatibilityTop ↑

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

Sexual Dimorphism

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

NotesTop ↑

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. In addition, colour pattern is variable and it’s not clear whether this occurs between, within, or both between and within populations.

In the original description Cope described the colour pattern of C. ambiacus 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 of the body around the base of the fin. Four vertical brown bands on caudal-fin, anal spotted. Cheeks with blue reflections.’

The snout is described as ‘elongate’.

In his description of C. agassizii, Steindachner noted 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.

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

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.


  1. Cope, E. D., 1872 - Proceedings of the Academy of Natural Sciences of Philadelphia 23: 250-294
    On the fishes of the Ambiyacu River.
  2. Ferraris, C. J., Jr., 2007 - Zootaxa 1418: 1-628
    Checklist of catfishes, recent and fossil (Osteichthyes: Siluriformes), and catalogue of siluriform primary types.
  3. Fuller, I. A. M., and H-G. Evers, 2005 - Verlag A.C.S. GmbH: 1-384
    Identifying Corydoradinae Catfish.
  4. Reis, R. E., S. O. Kullander, and C. J. Ferraris, Jr. (eds) , 2003 - EDIPUCRS, Porto Alegre: i-xi + 1-729
    Check list of the freshwater fishes of South and Central America. CLOFFSCA.
  5. Steindachner, F., 1876 - Sitzungsberichte der Kaiserlichen Akademie der Wissenschaften. Mathematisch-Naturwissenschaftliche Classe v. 74 (1. Abth.): 49-240
    Ichthyologische Beiträge (V).
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