One for real experts

[The-Wolf]

Here's one for all you real experts

What is the difference between a
Trigonostigma espei and a
Trigonostigma hengeli?

every picture I look at seems the same
I know T.espei don't grow as big as T.hengeli
but is that really it?

BTW I brought 8 T.hengeli last week and ordered in for the shop T.espei
I've compaired the two and they look the same. Of course it is possible the
same fish is being sold as two different species by the wholesalers.

Yours confuzzled
The-Wolf

 

[jfrancho]

I thought T. espei had more red coloration that almost completely surrounds the black, hence the "lambchop rasbora" common name. The Hengel's should have just a pinkish "hockey stick" above the black. To tell you the truth, though, I don't think I've ever seen them both at the same time in person.

 

[The-Wolf]

that would make sense
but then when you read about sexing, either one, you get
males are brightly coloured and females tend to be duller

 

[jfrancho]

That is the dreaded "females may be duller" escape clause. It really means that "the experts" only assume that the duller secimens in a shipment must be the females of that species, since the collectors would never mixup the species; yeah right. I have run into the same problem with wild caught peacock cichlids. You get a batch of a supposedly specific type, they eventually spawn, but you never know if you got the right female until the males of the spawn grow up and look like their father. If they don't, all that work is in the bucket. Though I think with enough time observing your fish and pictures in books and online, you'l be able to tell what you have.

 

[fishman 1]

I think you will find that it is merely down to a name change.

They were recognised as Rasbora hengeli.

The Federation of British Aquarist Society now judge the fish as Rasbora espei.

I have seen alot of these over the years and I think that there is definately more than one type/colouration variety of these fish.

 

[fishman 1]

With regards the sexing of them and colour. I find like a lot of fish it is down to the body shape. In more mature specimens it is easier. Females are fuller and can have less prominent colour (but not always).

 

[lljdma06]

I have seen T. hengeli or T. espie in my lfs. I don't know if this will help you wolf, but I googled both names and found this website that showed a picture of both T. espie and T. hengeli. Here is the link.

http/www.bollmoraakvarieklubb.org/artikl...nostigmaeng.htm

The other rasboras are lovely fish. They are right next to the Harlequins in the LFS I mentioned above, where they have the name "lambchop" rasbora, but the website calls them T. espie, so that will just add to the confusion. I was close to picking these fish, but opted for the Harlequins instead.

Sexing can be difficult, I still have to be careful with my harlequins, since their color has improved so much since I've had them. Good luck to you and your fish!

 

[The-Wolf]

Great link lljdma06

I think the my T.hengeli are half and half
that is to say I belive I have both T.hengeli and T.espei

I guess the only real way to find out is to seperate them and
try to get each "type" to spawn.

 

[Lateral Line]

A point that has been missed is that espei are a Mekong basin fish, whilst hengeli are an Indonesian species.

I susect that the fish now grouped in the Trigonostigma genus were once a single species and over time the geographical isolation of the populations has led to a small amount of divergent evolution.

 

[lljdma06]

A point that has been missed is that espei are a Mekong basin fish, whilst hengeli are an Indonesian species.

I susect that the fish now grouped in the Trigonostigma genus were once a single species and over time the geographical isolation of the populations has led to a small amount of divergent evolution.

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That is an excellent point. I was so focused on finding a good picture of each one that I didn't even glance at where they were from. It makes me wonder if members of that genus were kept together, would they hybridize?

 

[Lateral Line]

They may well hybridise.

I did a study a while back of Popondetta species, of which there are many. Because they have only recently been seperated and diversed, it transpires that almost all of the species will hybridise. The same is true of many rainbows.