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| Corydoras Look-a-likes 似て非なるコリドラス Ian A. M. Fuller
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Corydoras zygatus
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Corydoras rabauti
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Twenty years after I first spawned and raised the two look-alike species Corydoras rabauti La Monte, 1941 and Corydoras zygatus Eigenmann & Allen, 1942 there is still a great deal of debate as to which one is which. Here I will try to eliminate all doubt. The first point to establish is the fact that we are indeed looking at two distinct species, when the type specimens were examined, the differences between them were very small and the debate was whether in fact they were one and the same species. I spawned Corydoras zygatus on 21st April 1980 and then three months later on 23rd July my Corydoras rabauti spawned. Here I must say that I had not set out to prove anything, other than that I could successfully induce Corydoras species to breed. I had at that time successfully spawned and raised sixteen species, keeping detailed notes on all of them, especially the patterns of the developing fry. This was something that had interested me from my very first Corydoras spawning, the tiny fry of Corydoras pygmaeus were so different from the adults I thought it would be something worth keeping notes on. |
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Corydoras zygatus at 6 - 7 weeks
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Corydoras rabauti at 6 - 7 weeks
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The fry of Corydoras zygatus at 6 -7 weeks looked very much like many other species of Corydoras that I had spawned. It was not until the Corydoras rabauti had spawned that I saw a dramatic difference between the developments of the two groups of fry. The Corydoras rabauti fry were a stark contrast to those of Corydoras zygatus. Several specimens of fry from each spawning, along with an adult female from each spawning group were preserved and sent to Dr's Nijssen and Isbrucker for examination. Their conclusion was that they were indeed two distinct species having almost identical adult colour patterns. So how do we tell these species apart, with some difficulty I may say? Having kept both species for more than twenty years, I have become quite adept at separating them. The biggest setback is that they are usually imported together, although they come from different localities, because of their colour pattern similarity they are very often mixed together at holding stations prior to being exported. |
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Corydoras zygatus
Size: mature adults males 65 mm females 70 mm Colour pattern: Body light reddish tan, lighter on the belly. A dark broad dark grey band extends posteriorly, from the centre of the head just below the dorsal fin spine, along the dorsal scutes to the caudal peduncle and does not pass either into the caudal fin or onto the ventral scutes. There is a metallic green sheen covering the dark band. There is in most specimens a break in the band, which occurs on the scute adjacent to the dorsal fin spine.There is a light pink/orange patch below the band just above the eye. |
Corydoras rabauti
Size: mature adults males 45 mm females 50 mm Colour pattern: Body reddish tan, lighter on the belly. A dark broad dark grey band extends posteriorly, from the centre of the head just below the dorsal fin spine and along the dorsal scutes to the caudal peduncle. From where it extends across and down into the ventral scutes, then into the lower caudal fin. The band has a matt appearance with very little if any metallic overlay. There is a bright orange patch below the dark bank and above the eye, positioned in line with the dorsal fin spine. |
There is also another area where these two species differ; this is in the eggs that they produce. A single female Corydoras zygatus can produce in excess of 600 eggs in one spawning session. A Corydoras rabauti female on the other hand only produces up to 100 eggs. There is also a difference in egg size and the number laid at a time. Corydoras zygatus lays 1.0 mm diameter eggs and produces them in groups of 4 - 12 at each mating. Corydoras rabauti lays eggs that are nearly twice the size at 1.75 mm diameter but only produces 3 - 6 at each mating. The sites favoured to deposit their eggs by each of these species also vary. Corydoras zygatus prefer to deposit their eggs on solid objects near to the surface of the water; Corydoras rabauti however like to lay their eggs in a variety of places and at all depths, mostly they favour fine leaf plants such as Java moss, or the fine roots of plants like Java fern. Originally there was another species involved, Corydoras myersi Miranda Ribeiro, 1942 this proved to be a synonym of Corydoras rabauti, although I still see the name being used today. |
| (All Photo Credit and Text by Ian A. M. Fuller) |
| Ian A. M. Fuller: He is the Chairman of the 'Catfish Study Group (UK).' He has spawned 67 species of Corydoras, also has a large collection of Cory (105 known species and 6 unknown species). A book titled "Breeding Corydoradine Catfishes," which contains his breeding experiences, will be published soon (available on September 16th, 2001). |
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| Catfish Study Group(UK): The Catfish Study Group(UK) was born out of a group that originally formed in 1979 as a splinter group of the then 'Catfish Association of Great Britain'. We decided to change the name from 'The northern area catfish group' (It was based in the north west of England hence the name) and did so starting on January 1st 2000. We now have around 120 members including some from USA, Germany, Holland and Brazil. We produce a quarterly magazine and welcome catfish articles from anyone willing to write them. Along with each magazine we issue three information sheets, each of which contain details of a particular catfish, Scientific and aquaristic, with a line drawing and photographs of the particular species. The information sheets are at the moment my project and I do the line drawings and the lay outs. (Ian A. M. Fuller) URL: http://www.catfishstudygroup.org/ |
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| Japanese Abstract by kenken2 『似て非なるコリドラス』 by イアン コリドラス ジガートゥスとコリドラス ラバウティの2種類のとても良く似たコリドラスをご存知でしょうか。実はこの両種，稚魚のときは全く違った模様をしているのです。また一連の産卵における産卵数や卵の大きさも違うんです．．．（詳しくは本文で） 『イアンの紹介』 彼は現在イギリスのナマズ愛好家団体，"Catfish Study Group(UK)"の代表を務めています。20年以上コリドラスの繁殖に尽力し，これまでに繁殖させた種類は67種におよびます。このたび彼の繁殖成果が，"Breeding Corydoradine Catfishes"というタイトルの本にまとめられました。ナイセン＆アイスブルッカー博士とも親密で，彼の本の巻末にはアイスブルッカー博士提供のコリドラス全種カタログも加わります。 コリドラス好き必読！ |
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