To identify a true species from a hybrid

[Martin]

As far as I know there are 3 real discus species, can anyone enlighten me on the true species names and how to identify them.

Symphysodon aequifasciatus
Symphysodon discus
Symphysodon discus discus (Heckel ?)

The hybrid fish like blood parrot and flowerhorn are often discussed here in denmark. Is the regular discus a hybrid like those or is it different since they are in the same genus ?

[brewmaster15]

Hi Martin,
Unfortunately it really depends on who you talk to . Some maintain theres only one species...some believe 2 species....(heckels being one all others being in the other species.)

Its been debated over the years alot and truthfully no one really knows for sure...

My personal Beliefs, (read Beliefs strongly) based on my understanding of species as a biologist... I think the relative ease of breeding all discus except heckels indicates that the reproductive isolation needed for speciation to occur has occured or is occurring. Just my thoughts here.

I believe there are 2 species or two distinct sub species.... heckels and all else...examples of Closely related species abound in the wild..these interbred where they over lap..but are still classified as separate species.... prime examples... Black ratsnakes and Corn snake...they are separate species, but hybridize where they overlap.

I am not sure if we will ever really know and I think thats as time goes on and man artificially moves these populations around, the line between Heckels and all others will become more and more blurred...I think if speciation was occurring..It may not proceed.

JMO,
al

[sleonard]

Symphysodon Discus Heckel, 1840

Symphysodon Aequifasciata
- Symphysodon Aequifasciata Aequifasciata, 1903 (Green Discus)
- Symphysodon Aequifasciata Haraldi, 1960 (Blue Discus)
- Symphysodon Aequifasciata Axelrodi, 1960 (Brown Discus)

These are the species listed in Jack Wattley's Handbook of Discus but it is dated and, like Al said, many biologists think differently. Many think there may only be two, Heckels and Aequifasciata.

[wolfbane]

And all the beautiful colors came from these few species of discus? Wow!

[raglanroad]

There are many definitions of the word "specie".

Since every science uses different definitions to suit their own questions, it comes down to "what do you want "specie" to be defined as , for your question".

A check of science
encyclopedias should show a massive number of ways to interpret the word.

For our fish and, Kullander is a recognized authority on meristics or counts and measurements of fins and scales, etc. and taxonomy. But there is a large amount of unfinished business.

Izeni Farias has just done the latest study on discus DNA and it is being published soon. She had already done a wider study on phylogeny I think.

http://golab.unl.edu/people/izeni/index.htm

[Ichthyology]

First and foremost.....there is no such word as "specie". The plural and singular of the word is SPECIES (Sorry, it is the professor in me....two phrases I hate..."specie" and "tuna fish"...what else is tuna if not a fish!!!!!)

I for one believe that there is only on species of discus with numerous subspecies (or races...or morphs...). The present classification is:

Symphysodon discus
Symphysodon discus discus
Symphysodon discus willischwartsi

Symphysodon aequifasciata
Symphysodon aequifasciata aequifasciata
Symphysodon aequifasciata haraldi
Symphysodon aequifasciata axelrodi

The original counts conducted on S. discus have never been replicated (in fact, people who have looked at the actual fish do not record the same counts). There was only 1 distinct count that separated the two species. Work by my students and I in the past have shown that all meristic counts over lap.....

So what does that all mean...............yes, a species is an artificial thing. What we do seem to have are a bunch of isolated populations with specific traits (color, striations, etc) being "fixed" in particular populations......Marc Weiss and I had a chapter in Ad Konings Cichlid Yearbook published on this many years ago where I outline the problem......

[raglanroad]

Thanks Ichthy.
I don't know why I adopted that during "net' discussions. Anyway, we have been looking at the same thing you describe as "overlap of counts", with angelfish.
Not only that , but other problems seem to be involved. Isn't it true that at least one species had the males classified as a different species from the females - it was unknown that they were the same fish ?
I believe we have discussed some of your work on the angel forum, I remember a comment from Marc I think, about finding several different coloured discus under one log.

Which definition of "species" do you use in this case, Ichthy , when you conclude there is only one species of discus ?

[Rod]

Peronally i think 1 species Symphysodon discus, but with several subspecies (geographic forms!?).

[Ichthyology]

As a standard, I use the "Biological Species Concept".....takes into consideration interbreeding (see below). One of the problems we had originally with discus is that they all appeared to be geographically isolated from each other to a certain extent. Thus color traits could become easily fixed in each population. So what may have been happening is that they were on their way to speciation...(in a million or so years). Now that color morphs seem to have been transplanted and moved all over the place in the Amazon (just look at the Rio Nanay discus as an example), it is harder to pinpoint everything down.

Do the 2 species of discus interbreed in the wild? Not sure. Can they breed in captivity? Sure, but is this an artificial thing from captivity? If they do interbreed is their fecundity (repro output) the same???

[raglanroad]

http://b.casalemedia.com/V2/53492/69558/index.html?www.studyworld.com/newsite/reportessay/Science/Biological%5COver_the_last_few_decades_the_Biologi cal_Species_Concept_(BSC)_has-4

Ichthy, I think this article points out some of the problems in defining "species".
The Heckel would fit as a separate species easily under some definitions; Interbreeding - even if producing a few less offspring - would allow the phylogenic concept to be applied wouldn't it ?

Outbreeding depression could reduce clutch size and so on, while still within the species, even in classical biological concept framework.

The phylogenic concept seems to avoid the problem in a way by making the definition less strict regarding breeding, but must show some evidence as to relationships. And so it goes...real animals don't fit the boxes...so the scientists would seem to use whatever classification method suits the type of work they do.
Is this correct ?
http://persoon.si.edu/sbsarchives/sbs2001/abstracts.cfm

Dave

[Lee C]

I believe there are 2 species or two distinct sub species.... heckels and all else...examples of Closely related species abound in the wild.

I am with AL on this topic!

Lee

[fishfarm]

I import a lot of wild discus, There seems to be no diffenitive color morph, In a batch of wild blues you can get almost solid brown/red fish, fish with full body striations, fish with red spots, and or heckel bars, all caught in the same area, Where the different "subspecies" overlap in the wild they freely interbreed. So I am of the opinion that there is really only one species with many geographic color morphs, if anything only two with heckel being the other species from aquafaciatus. Ken