Identifying Corydoras

Author: Ian Fuller

Identifying the many species of Corydoras is becoming more and more difficult there are a considerable number of species that can easily be mistaken for others that are similarly marked. Here I will try and show some of the characteristics that may help to separate some of the species that come into the trade as 'Corydoras punctatus', bearing in mind that these are only my opinions and should be used as a guide and not to be taken as fact. As I go through groups of species it will lead into other confusions and bring in species that are possibly new and yet to be described by science. The most obvious solution would be to have a picture database of all known species, which could then be used for comparison unfortunately we don't have that luxury although the Aqualog 'All Corydoras' book comes close.

Today there are increasing numbers of Corydoras species that are arriving in our shops, which have names that have been made up, either by the catcher or the exporter. I have known the same fish turn up on three consecutive shipments with three different names this is invariably a ploy by the exporter to sell fish he would otherwise be stuck with. The opposite also happens when exporters call every other black spotted Corydoras, Corydoras punctatus. Having said that I think this is a good place to start unraveling some of these spotted species. The main species that are imported under the guise of Corydoras punctatus are usually C. ambiacus, C. agassizii, C. leucomelas, and C. schwartzi. This is something that should never have occurred in the first place, because Corydoras punctatus does not come close to looking like the other four, Firstly it is the only one of the five species that does not have a dark mask across the eyes. The body which is whitish is covered with small to medium round black spots, the other four have irregular shaped blotches all over their bodies and in some specimens those blotches along the sides blending into irregular rows. All except Corydoras schwartzi who's dorsal fin spine is creamy white in colour, instead of a large blotch or bar or as well as in some cases, there are two or three rows of small horizontal blotches, which in some individuals may be hardly visible. This is one of those species that can show a wide variation of colour pattern within a single population. The other four have large black areas in their dorsal fins, in each species the black area is very distinctive and should be one of the best characters by which to differentiate each of them.

Corydoras punctatus has a large round to oval black blotch that is situated more or less centrally in the dorsal fin. Corydoras ambiacus has a black area that starts below the first three or four dorsal fin rays and extends upwards into the dorsal fin, reaching to approximately two thirds of the way up. Corydoras agassizii is very similar in appearance to Corydoras ambiacus, and at times it is very difficult if not impossible to differentiate between the two species. Where they do tend to differ visually is in the dorsal fin bar/blotch, compared to Corydoras ambiacus Corydoras agassizii has dark brown to black pigment that extends from the body covering the full length of the first two sometimes three soft dorsal fin rays, again this can be variable in size and intensity from one specimen to another.

The size, orientation and colour of the body blotches of both species are so variable, ranging from a medium tan to dark brown almost black, and to separate them by body markings alone is impossible. Corydoras leucomelas is somewhat smaller and stockier than the previous two species and its colour is more defined, the body is white covered with smallish jet-black blotches, which can also be quite variable in size and distribution and in some specimens they may form irregular rows. There is a largish black diamond shaped blotch that is fairly evenly dispersed on the body and dorsal fin.

Corydoras schwartzi also has a white body and is a fish that has a similar stature to that of Corydoras leucomelas but it does grow a little larger. It to has black irregular blotches, which are larger than in Corydoras leucomelas and that form four or five bands that run the length of the body. These bands may be quite variable being very distinctive in one specimen and hardly discernable in another. A point to note with this species is that the bands along the sides of the body are positioned on either side of the juncture of the dorsal and ventral scutes, which is a feature that separates it from two other similarly marked species all of which have an irregular band or row of blotches along the centre of the body as well as rows above and below. These species are Corydoras ornatus, and Corydoras pulcher then there's Corydoras parallelus, which is even closer looking showing an almost identical pattern.

Both Corydoras ornatus and Corydoras pulcher have a row of blotches that extends back from the head along each side of the body to the caudal peduncle. In the case of Corydoras ornatus there are a further two rows either side of the central one, and in Corydoras pulcher there is one on either side with a dark ridge that runs the full length of the back. The blotches on Corydoras ornatus very rarely combine to form solid bands, but in Corydoras pulcher the opposite is the case where the blotches join to form broad bands. The final species is Corydoras parallelus which when compared to Corydoras schwartzi looks very much the same, the body markings are displayed in exactly the same areas the difference being in Corydoras schwartzi the blotches form broken bands rarely being fused to form solid bands. Corydoras pulcher on the other hand has blotches that do merge to form solid bands, it also has a large black diamond shaped blotch covers most of the front half of the dorsal fin and extends down the body as far as the juncture of the dorsal and ventral scutes. A further difference is that Corydoras schwartzi has blotches in the caudal fin, that form up to eight irregular vertical bars and Corydoras parallelus has an almost clear caudal fin.

Article reproduced by kind permission of Ian Fuller of www.corycats.com

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