Corydoras Hybrids

[OddOscar]

I just bought 5 Corydoras the other day, 4 Bronze and 1 Peppered. Since I heard it's ok to mix different species of Corys, I was wondering if Corys ever interbreed and make hybrids? I hear all the time how you should never mix different African Cihclids species because they will breed together and form hybrids and thats bad, but why don't I ever hear of Corydoras hybrids and how bad those are?

[Richard B]

There are occurrances of cory hybrids but they are much scarcer than cichlid hybrids

[MatsP]

I'd expect that bronze corys and peppered corys will not cross-breed. However, the best way to avoid it is to keep a large enough number of both sexes in a group - then the fish will recognise it's own kind, and breed within the group, rather than cross-breed.

--
Mats

[apistomaster]

I don't think paleatus and aenus would ever hybridized.

I may have missed any other reports but I don't know of any different Corydoras spp have ever been hybridized

[Borbi]

Hi Larry,

Ingo Seidel reported on the unintended hybridization of C. panda with C. sterbai (and published some pictures of the outcome), so at least it is possible. But that surely depends on how closely related the species in question are. There are probably a few other reports that I don´t recall right now. But I agree, I also doubt that C. aeneus and C. paleatus will hybridize just based on the fact that these two species are around for about 100 years and easily bred, so if it was possible (without use of hormones), we most likely would know about it.

Cheers, Sandor

[MatsP]

There was a post some years ago about Corydoras hybrids - it had a list of species known to hybridize naturally and with hormone injections - the list was about 15 or so that do it naturally and about 20-30 that need hormones to "do it". Given the overall number of species, I'd say that's a pretty small list.

--
Mats

[Olivier]

I have one little hybrid, so it is possible (not from the C. aeneus or C. paleatus).
But I think that the C. paleatus and C. aenus never make a hybrid, they are to differed.

@Mats: I'm very interested in that post!

[OddOscar]

I read somewhere were they crossed Corydoras panda with C. paleatus.

Here is another question, If two different fish reproduce and the babies are fertile, would the two different fish really be one in the same?

[Bas Pels]

I read somewhere were they crossed Corydoras panda with C. paleatus.

Here is another question, If two different fish reproduce and the babies are fertile, would the two different fish really be one in the same?

I can't say i understand the question fully. Assuming you intended to ask: does the possibility to reproduce and produce fertile fry imply the parents are the same species, I'd say, in general, no.

Almost all central American cich lids can interbreed. Those which don't interbreed with eacht other might both interbreed with a third species, but I would not consider say a Parachromis dovii (growing to 50 cm or more, eating fish, mostly cichlids) conspecific with Thorichthys meeki (max 15 cm, a sandsifter) or Herichthys cyanoguttatum (max 30 cm, generalized feeder, but almost sub-tropical, living as far north as Texas)

However, personally, not hindered by any relevant knowledge, I think the 200 or so species of corydoras, including the undescribed varieties, is more than needed. I think the scientists who describe Corydoras (and other groupes, such as Rhineloricaria) see new species far too easily. But in order to support this point, I would have to proove that a few species are actually one and the same - and I lack the knowledge, equipment and money to do so.

And if I had these, I would most probably work with other fish than Corydoras

So perhaps I better not go deeper into this

[Hitch]

just another point to add on, since when kept in the right numbers, in most cases, corys from different species would not even school together. Thus, the chances of them hybridizing is slim to none.

[mummymonkey]

Some species seem to be more prone to hybridisation than others - metae is a case in point. Also all the elegans type species will cross with each other. I have personal experience of the following hybrids, which all produced fertile young, and came from tanks with both sexes of each species present.

metae x axelrodi
billineatus x nijsseni
burgessi x C121 (C121 may be burgessi anyway)

[MatsP]

Here is another question, If two different fish reproduce and the babies are fertile, would the two different fish really be one in the same?

That's not true. It's true to say that two species that can not produce fertile young are definitely separate species. But there are far too many fish that are clearly not the same species [1], for example, we would not think that

Hypancistrus zebra

and

Hypancistrus sp(L066)

- as they hybridize and I'd be very surprised if they are NOT fertile young.

[1] Obviously depending on how you judge things. One could of course say that by looking at the the exterior, it's quite clear that a Chiuaua(sp?) is not the same species as a St. Bernard or a German shepherd dog? But in my personal opinion, if the wild create looks VERY different, and also has morphologicial (measurement of the body and counts of for example rays in fins and bones in the body) differences, then there is a good argument that they are different species.

--
Mats

[OddOscar]

I can't say i understand the question fully. Assuming you intended to ask: does the possibility to reproduce and produce fertile fry imply the parents are the same species, I'd say, in general, no.

Yes, I know I should of written the question a little better but I couldn't think of another way to say it, thank you for answering. Thank you everyone, these answers are exactly what I was looking for.

[racoll]

The reproductive incompatibilities that will prevent different species from producing fertile offspring, occur quite late in the speciation process. This one of the final patterns to be observed that signify that two populations have acquired independent evolutionary paths (i.e. they are different species).

The biological concept of species treats this point (infertile offspring) as when species should be recognised, but the problem with this being, that it does not recognise a huge amount of diversity that has a younger history, but shows a clear independent evolutionary trajectory. It is also not practical; in order to test whether something is a new species, you would have to capture it alive and try to breed it in captivity with other closely related forms. This is not possible or necessary for many reasons.

A better, more practical approach (i.e. the phylogenetic species concept) is to look for consistent, unique patterns in morphology or DNA that indicate that lineages have diverged, and that little gene flow is taking place between the two populations. If evidence is sufficient, and non contradictory, a new species can be recognised.

This is how modern taxonomy works!

[Carp37]

However, personally, not hindered by any relevant knowledge, I think the 200 or so species of corydoras, including the undescribed varieties, is more than needed. I think the scientists who describe Corydoras (and other groupes, such as Rhineloricaria) see new species far too easily. But in order to support this point, I would have to proove that a few species are actually one and the same - and I lack the knowledge, equipment and money to do so.

And if I had these, I would most probably work with other fish than Corydoras

From a similar position of (lack of) relevant taxonomic knowledge, I agree with Bas Pels' comments re Corydoradinae- I think eventually we'll lose some species as junior synonyms and gain a fair few new ones. I'm not sure why the subspecies taxon seems to be so out of favour now, but to me it seems likely that a number of the newer described species are just a racial variant of existing species. I've no objection to these being given C- or CW- numbers as it's still useful to differentiate groups of (slightly) different fish, as long as they're true-breeding and having minimal interbreeding with other populations, but the subfamily does seem to be very much in favour of splitting rather than lumping fish. I'm also not mad keen that we've still got a paraphyletic genus in Corydoras (as some species of Corydoras are closer to Brochis, or Scleromystax, than to some other species of Corydoras).

[MatsP]

There is work in progress that uses DNA analysis of MANY (all scientifically described?) species of Corydoras, and one possible conclusion of that was that there may be as many as 7 different genera or Corydoras. Brochis would be merged in with several regular Corydoras species, apparently. However, until that work is published, I guess we'll have to stick with what we have today.

The subject of "what is a species and what is not" will probably continue for a long time - and I think DNA analysis would certainly be one way to say for sure.

--
Mats

[kim m]

There is work in progress that uses DNA analysis of MANY (all scientifically described?) species of Corydoras, and one possible conclusion of that was that there may be as many as 7 different genera or Corydoras. Brochis would be merged in with several regular Corydoras species, apparently. However, until that work is published, I guess we'll have to stick with what we have today.

The subject of "what is a species and what is not" will probably continue for a long time - and I think DNA analysis would certainly be one way to say for sure.

--
Mats

The work those guys are doing is massive, no less! As you say it is not public yet but as I've contributed with dead fish and/or fin clips from a lot of my species I have a bit of insight in the work and I'd call it groundbreaking

Very excited to see the finished project!

[MatsP]

Kim, I'm very interested in the results too - even if I haven't contributed to it.

--
Mats

[Carp37]

The work those guys are doing is massive, no less! As you say it is not public yet but as I've contributed with dead fish and/or fin clips from a lot of my species I have a bit of insight in the work and I'd call it groundbreaking

Very excited to see the finished project!

I'd be very interested to see it too Kim

The subject of "what is a species and what is not" will probably continue for a long time - and I think DNA analysis would certainly be one way to say for sure.

I think we'll probably never have an answer to this- the problem here is there's no right or wrong answer as to when geographically distinct (allopatric), non-interbreeding populations are considered separate species or simply regional variants- it's a purely subjective view (which gets more subjective still at genus level). At what point does one decide that two populations are sufficiently divergent to be classed as separate species? DNA analysis WILL tell you how divergent they are (at least for the base pairs sequenced) but I don't think there's a standard degree of differentiation that's used to say "right, they're different enough to be separate species".

As to looking at clades (evolutionary groups) within the corydoradines, DNA analysis should hopefully produce much clearer results. My PhD was in goby systematics (16-20 years ago!), but using isozyme electrophoresis rather than DNA sequencing- the latter should be several times more reliable in identifying differences than gel electrophoresis (and much more suited to cladistic analysis for determining common ancestry).

[racoll]

the problem here is there's no right or wrong answer as to when geographically distinct (allopatric), non-interbreeding populations are considered separate species or simply regional variants- it's a purely subjective view (which gets more subjective still at genus level). At what point does one decide that two populations are sufficiently divergent to be classed as separate species? DNA analysis WILL tell you how divergent they are (at least for the base pairs sequenced) but I don't think there's a standard degree of differentiation that's used to say "right, they're different enough to be separate species".

Very true Carp37, although I think having reciprocally monophyletic genealogies for a selection (minimum two) of both mitochondrial and nuclear genes is pretty good evidence. The problem with this being that due to stochastic processes, genes can remain paraphyletic long after a speciation event, and relying on this diagnosis would ignore a lot of the younger diversity. If it can be demonstrated that populations are divergent, and can be reliably defined by clear synapomorphies (unique shared features) be they DNA or morphological, I believe they should be referred to as different species.

I'm not sure why the subspecies taxon seems to be so out of favour now, but to me it seems likely that a number of the newer described species are just a racial variant of existing species. I've no objection to these being given C- or CW- numbers as it's still useful to differentiate groups of (slightly) different fish, as long as they're true-breeding and having minimal interbreeding with other populations,

I'm not really a fan of the subspecies taxon, and I am glad they are no longer used in ichthyology. In ornithology and entomology, however, they are rife.

My main problem with them is that they are used under the biological species concept to denote groups of similar species (i.e. a species complex) that are different and could interbreed if they had the opportunity, but are not able to interbreed at the species level.

As I stated earlier, this to me is not a testable hypothesis in the real world, and as such renders their use obsolete.

Subspecies have often been used in the past to describe different colour/pattern forms of essentially the same, but variable species. Research has suggested that only 50% of bird subspecies (3% in Nearctic and Palearctic) represent evolutionarily distinct lineages.

I do like they way they tell you what the closely related forms are, but I feel they unnecessarily confuse an already confusing situation, and that species should be the lowest unit of diversity in the Linnaean system.

[Gordon C. Snelling]

Sadly tis true that in entomology the subspecies concept is still quite popular esp among the beetle and butterfly crowd. However it is falling out of favor here as well. I one for one am glad to see it go. In the group I work on, (ants) there are numbers of subspecies to deal with which really muddy the water, but they are going away. I shall be starting a short work soon in which several subspecies of army ant will be going away.

[Carp37]

Interesting points raised by Rupert and Gordon- I'm still not sure if there will ever be consensus as to the amount of differentiation required to categorise a species (rather than a divergent population which may or may not be "on the way" to being a separate species), but your points make interesting reading.

[MatsP]

Well, the way that Mark Sabaj explained it at Catfish Study Group is that a scientist proposes a theory that "This fish is a new species, and here is why <several pages of text>". Other scientists will then either accept or refuse the newly described species. Acceptance is measured in references in other scientists work, mainly. If a scientist strongly disagrees, he/she will produce another paper saying so.

--
Mats

[Gordon C. Snelling]

Yes indeed pretty much the way it works with new species and such. Prior to publication though it is hoped that the author has done his research well and will listen to any reviewers of the paper and make changes needed to it to increase the likelihood of acceptance.
Just recently there was a fella publishing new ant names for species for already named and very common central American species. A real mess.

[racoll]

the way that Mark Sabaj explained it at Catfish Study Group is that a scientist proposes a theory that "This fish is a new species, and here is why <several pages of text>".

Exactly. A species name is hypothesis of relationship, not a cast iron fact. This is a concept that a lot of people struggle with when they moan about taxonomists changing names. A species name is supported by the empirical evidence presented in the description/revision.

Acceptance is measured in references in other scientists work, mainly.

Yes, sort of. If a name however satisfies the conditions of the ICZN, then it is an available name, and cannot be ignored, no matter how bad the taxonomy is.

Prior to publication though it is hoped that the author has done his research well and will listen to any reviewers of the paper and make changes needed to it to increase the likelihood of acceptance.

The peer review process is important in this respect, as it will weed out any dodgy descriptions. This is why one should not publish new names in aquarium journals, as there is no peer review!