Corydoras, The Long and the Short

Author: Richard Guest of Pets Parade Team

Within the genus Corydoras there is a wide variation in body shape and size, particularly the head and snout. There are those that we term the 'Rounded' or 'Short nosed' group at one end of the scale and then there's the 'long nosed' or 'Snouted' species at the other. In between these two extremes are other head shapes where several species can be categorized, which is what I tend to do mainly for my own convenience. What the various shapes indicate to me is, that in all probability these species inhabit the same or very similar environments, feed in the same manor and on the same or similar types of food. This then helps when I prepare tanks for new acquisitions, by giving them the right set of conditions from the start.

Why several groups of species have developed these different head, snout and or body shapes is something that can only have come about through the evolutionary process where species needed to take full advantage of a particular ecological niche and therefore able to access a food source that others cannot.

With most catches of wild caught fish there can be found the odd few specimens of one or several different species, these are often referred to as contaminants. With these so-called contaminants, many of which I have found to be long snouted species. We tend to think of these contaminants as uncommon or even rare, but there is every possibility that there are naturally far greater numbers of them living within the populations of the more plentiful rounded or short nosed species. When collectors are segregating their catches to keep them pure species, they miss some of the long snouted specimens these are then exported with the main stock. The fact that only a few of these long snouted species get through to our wholesalers, lead us into believing that they are far fewer in number in and rarer the wild than they in fact really are. There is also yet another twist to this saga, in as much as if a collector has not collected enough of a particular species he will invariably add some other similar looking species to the batch, in order to make up the numbers and consolidate his order. On one hand I like this practice because we get to acquire some of the otherwise lesser known species, the down side with this practice as far as we the hobbyist is concerned is that these additional fishes may not have been collected in the same area, or even come from the same river as the ones to which they have been added. This in its self in most cases makes for nigh on impossible identification of the contaminant species, because to be absolutely sure of a species identification the collecting locality in needed, then these details can be cross referenced to scientific papers. These location details would also be needed by science to enable the description of a new species to take place. Because of the rarity of some of these species and the hobbyist demand for them, makes them a valuable commodity then the localities become very closely guarded secrets.

The following are a few examples of groups of species that could be considered as having the same head and snout shape.

1. Long snouted. (Concave) C. acutus, C. amapaensis, C. vittatus, and C. treitlii.

2. Snouted. (Straight) C. haraldschultzi, C. pulcher, C. spectabilis and C. robustus.

3. Snouted. (Convex) C. arcuatus, C. copei, C. delphax, and C. gomezi.

4. Slender Snouted. C. prionotos, C. kronei, C. macropterus C. lacerdai

5. Rounded. C. trilineatus, C. duplicareus C. sterbai, C. araguaiaensis.

6. Short Rounded. C. metae, C. atropersonatus, C. concolor , C. caudimaculatus.

7. Even dorsal/ventral profile. C. elegans C. napoensis C. guapore, and C. pygmaeus.

One of the most interesting things that have transpired over the last few years is the emergence of both long and short nosed species, which have virtually identical colour patterns. In some cases these look-a-likes inhabit the same waters and can therefore be considered as mimics. Which of the two species should be called the mimic would be difficult to determine and open for debate. Where there is a large population of one species with fewer numbers of another having the same or similar colour pattern, all of which are living within the one group, I think it would be reasonably safe to say that the species of fewer numbers is the mimic.

In other instances we see species with similar if not identical looking colour patterns, that cannot be considered as mimics because they are separated geographically therefore do not have the need to be able to blend in with the majority species. It is my belief the reason for the colour similarity between them is purely evolutionary, with each of species possibly inhabiting completely different river systems that may be separated by many hundreds of miles. The similarity in colour patterns is purely coincidental it could very well be that the species have evolved in very similar if not identical bio-systems, where the need for camouflage or recognition coloration is the same.

In some of the importations that I have seen and helped to unpack, I very often come across long snouted specimens that would be considered contaminants in amongst the main stock species. This is in fact quite a common occurrence with two or three species in particular. In shipments of Corydoras melini Lönnberg & Rendahl, 1930, I very often find several specimens of Corydoras septentrionalis Gosline, 1940. In amongst Corydoras metae Eigenmann, 1914 we very often come across a few specimens Corydoras simulatus Weitzman & Nijssen, 1970. Another more recent discovery was with a largish shipment of around five hundred Corydoras habrosus Weitzman, 1960 in amongst these we found eight specimens of a long nosed species that is only known as 'long nosed' Corydoras reynoldsi Myers & Weitzman, 1960 This is probably a species that has yet to be described. Of the six species mentioned only two C. metae and C. simulatus were discovered from the same locality. C. melini and C. septentrionalis are geographically separated by many hundreds of miles, which give weight to my theory that the species are being mixed together at the exporters holding stations.

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Corydoras, The Long and the Short

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