Sterbai with other corydoras?

[plecc83]

Hi all,
Which Cory's can be kept together in groups without risk of cross-breeding?
I currently have a 4 foot tank with a group of Sterbai and a group of Northern Longnose, are there some other species that would be compatible?

 

[Byron]

There are a couple of factors at work here, respecting hybridization or cross-species spawning.

In nature especially at a time when severe conditions bring two distinct species together that would not normally be found in the same place, it can sometimes result in cross-breeding, known as speciating. We can leave that as the question is in reference to the fish we keep in our aquaria.

If the individual species has male and female in the aquarium, it is very unlikely to hybridize. I cannot say it definitely will not, but Ian Fuller says it is extremely unlikely if both genders are present. With just one gender of a species, and within the confines of an aquarium, there is evidence that some species will hybridize; I have had this more than once in my own tank when a solitary female of C. axelrodi has spawned with one of two male C. metae (the patterning of the fry is pretty suggestive it is these two species). I do always try to get five, or at minimum three, of a species, but over time they can sometimes die off, leaving one or two (same gender). Or the store may only have the one, two or whatever to begin with.

This brings me to the "some" species, and here we encounter the lineages within Corydoras. “It is clear from the molecular phylogeny that the Corydoradinae are in need of taxonomic revision. The need for this revision has been recognized for some time (Isbrucker, 2001), although it is only now that the genetic relationships among species are clear, allowing species to be grouped into phylogenetically meaningful and monophyletic groups." (Alexandrou & Taylor, 2011). A monophyletic group or clade is one in which all members have descended from the same common ancestor. The genus Corydoras is polyphyletic, in that there are nine different ancestors now recognized. And that brings us to the hybridization issue. Species within the same lineage are more likely to hybridize, so avoiding combining species of the same lineage will most likely avoid hybridization.

You mentioned C. sterbai...this species is in lineage 9, which with (currently) 154 described and undescribed "C" species, is the largest assemblage. I've no idea what species Northern Longnose refers to, so can't see where it may sit.

 

[plecc83]

Wow Thankyou Byron, amazing answer!

I should have referred to the Northern Longnose as "corydoras septentrionalis"
Here is a link to a basic info sheet from one of my local fish stores -

Northern Long-nosed Cory-Corydoras septentrionalis

Expert facts, care advice, feeding tips and breeding information about the Northern Long-nosed Cory (Corydoras septentrionalis) for freshwater aquarium enthusiasts.

www.fishkeeper.co.uk

And a more detailed info sheet from planetcatfish -

PlanetCatfish.com - Corydoras septentrionalis (Callichthyidae) Cat-eLog

Images are copyright and may not be reproduced without permission of the copyright holder.

www.planetcatfish.com

Funny you mentioned Ian Fuller, I was watching a few of his short youtube videos earlier today, small world!

Do you know of any resources I could use to gain a better understanding of the different lineages of corydoras?

 

[Byron]

You are very welcome. I may have a bit more for you...

Corydoras septentrionalis was described by W.A. Gosline in 1940 in the Stanford Ichthyological Bulletin v. 2 (no. 1), which I haven't been able to find online. I spotted in your first linked site the mention of Corydoras cortesi being a synonym so I followed that up, and for a time it was thought to be, until 2016. Apparently this is referenced in the description paper of a new species, Corydoras zawadzkii, described by Tencatt & Ohara (2016); here's a link to the paper, you could have a read and see if anything interesting pops out, but the two species are now deemed valid distinct species.

https://www.researchgate.net/profile/Willian_Ohara/publication/305683019_A_new_long-snouted_species_of_Corydoras_Lacepede_1803_Siluriformes_Callichthyidae_from_the_rio_Madeira_basin/links/579a05ba08aefaeb30a99bf7.pdf

C. septentrionalis occurs in lineage 1, so it would be highly unlikely to hybridize with C. sterbai.

I know Ian Fuller, online that is, we have corresponded, and I belong to his FB page Corydoras World. So does Dr. Luiz Tencatt, who has described more than 20 new species over the past few years. There are resources on the lineages available to members.

 

[Byron]

On the Corydoradinae lineages, it occurs to me that you might find some good information in Marcelo Britto's paper "Phylogeny of the Subfamily Corydoradinae Hoedeman, 1952 (Siluriformes: Callichthyidae), with a definition of its genera," Proceedings of the Academy of Natural Sciences of Philadelphia 153, pp. 119-154 (December 2003). This is accessible free online (link below).

There is considerable scientific data obviously, but Dr. Britto's conclusions have been accepted by subsequent ichthyologists, though much work remains to be done before this family is sorted out phylogenetically. Two major proposals resulted.

The species Corydoras barbatus along with two other species was found to be a distinct lineage from Corydoras; under the rules of the ICZN the oldest name assigned to a clade (genus in this case) must be used, so Britto reinstated Schleromystax, and the species are now in that genus with Schleromystax barbatus as the type species; a few new species have since been described in this genus. All of these fish occur along the eastern edge of Brazil, upriver in fresh water (not coastal). This clade is lineage 4.

The second major change was the three species in Brochis. Britto discovered that a handful of Corydoras species are phylogenetically closer to Brochis, which makes Brochis non-monophyletic. Britto synonymized Brochis with Corydoras, and "officially" the species are now Corydoras splendens, etc, and not Brochis splendens. Some are unwilling to accept this yet, with valid concern over the external physical differences, and subsequent ichthyologists have provided additional data concerning this lineage 8 which contains these species, and proposed four sub-clades, the first of which would be the "Brochis" species.

The species in Aspidoras are in lineage 2. Luiz Tencatt has carried out the most comprehensive study of the species in this genus in I believe 30 years, and his paper is linked on CW though not yet published.

https://www.academia.edu/download/38301357/Britto_2003.pdf

 

[plecc83]

Thanks again Byron!

The first publication is very interesting.
Unfortunately some of the terminology goes straight over my head, but I'm starting to get a feel for it.
Thank you for explaining how the species definition has evolved over the years.
Great to hear that I shouldn't hopefully have any issues with my current cory's.

I have my eye on a few cory's from lineage 7, especially C. hephaestus (Fireball Cory), but I haven't ever seen them locally. One of the LFS has some really nice C. eques at the moment.
Are the corys in lineage 7 all descendants of the C. aeneus (Bronze cory)?

I wasn't able to access the second document, I think it may be due to regional restrictions. I will try again using a VPN.

I will try to get a nice pic to add to the post, they are stunning little catfish.

 

[Byron]

Are the corys in lineage 7 all descendants of the C. aeneus (Bronze cory)?

No. Each species within each distinct lineage has evolved from the same common ancestor, not from species within the present lineage. An evolutionary lineage is a line of descent of a taxon (which may be a species, genus, family) from its ancestral taxon. The Callichthyidae family has two subfamilies first defined by Hoedeman in 1952, the Callichthyinae and the Corydoradinae; the latter contains the Corydoras, Aspidoras, Schleromystax, Brochis genera which together hold some 90% of the species in the entire family--170 described, not including the dozens of "C" and "CW" number possible species. Alexandrou & Taylor (2011) suggest that the group are likely very old, with a fossilized Corydoras (Corydoras revalatus) described from the Maiz Gordo Formation of Argentina (Cockerell, 1925), dated from the late Paleocene.

The first Corydoras species described in this genus was C. geoffroyi Lacepede, 1803 and he designated this species as the type for the new genus. C. aeneus (Gill, 1858) was originally described as Hoplosoma aeneum by T.N. Gill in 1858; I believe it was moved into Corydoras by Nijssen and Isbrücker (1980). Unless there is another species I am not aware of that predates, once the lineages are sorted out, the actual genus Corydoras will have C. geoffroyi as the type species, since the rules of the ICZN require that the oldest name assigned to the genus must prevail. This is lineage 1 and as I say it retains the genus name.

The "aeneus" group of species are lineage 7, and will have a new genus name, presumably (Alexandrou & Taylor, 2011) Osteogaster (Cope, 1871) with C. eques Steindachner, 1876 as the type species for that genus; since the genus name will change, the species will then be known as Osteogaster eques (Steindachner, 1876). The parenthesis around the describer's name signifies that the genus has changed since the species was first described by that individual.

I have a chart showing the phylogenetic relationships of this subfamily; I must give credit properly, and I believe it came from Ian Fuller.

 

[coriesinhawaii]

For what it's worth I've had a single sterbai cory (not sure if male or female) in with my shoal of peppered cories for a couple of years and while the peppered cories spawn regularly the sterbai has never showed any interest in their shenanigans. I was finally able to get a couple more sterbais recently so my original sterbai finally has some buddies now.

 

[plecc83]

Hiya,
Apologies for the slow reply.
Here you go, this is the best pic I could get. They are really active for cories and my photography skills are a bit weak
I will try to get a few better ones of both male and female in a day or so when I give the glass a good clean.

My largest female 50mm approx. The pic doesn't really do her justice, the brown/black areas over the head and back have a very nice silvery-blue iridescent sheen that really catches the light.
They are a bit more active than you typical cories, a little more boisterous and have an amazing appetite.

Ah I see, thanks so much for taking the time to clear that up.
Oh wow, the phylogenetic relationship chart is great! I may have to laminate myself a copy.

Thanks coriesinhawaii,
Good to hear that I shouldn't have any issues.

I will try to add a few more photos.