hengeli rasboras

[jasong55555]

probably stupid question but will hengeli rasboras and red rasbora hengeli school together?

 

[Essjay]

The top photo is Trigonostigma hengeli, and the bottom photo is Trigonostigma espei, more properly called Espe's rasboras rather than red Hengel's rasboras. They are two different species.
As to whether they will shoal together, I'm not sure. They might because they are related, but it would be better to have just one species if possible.

 

[Byron]

I agree. They will shoal together; I had an old group of T. espei years ago that were dying off from old age and I decided to change to T. hengeli, so I put the new T. hengeli in with the old T. espei and they remained together in a tight shoal until the last of the older fish died. I have also done this with the cardinal tetra and false/green neon tetra, Parachierodon axelrodi and P. simulans, and my two very old cardinals are right in as if they are the same. Similar with the hatchetfish in Carnegiella, and even Carnegiella and Thoracocharax species. This does not work with all species in every genus however, it depends upon the genus.

And I also agree not to combine the two rasbora species normally, as with new fish; have one or the other, in suitably-sized groups (at least 7, preferably 9 or more). This non-mixing of closely related species is a principle that is standard in the hobby. Usually the different species in a genus would never come across each other in nature, and hybridization cannot always be ruled out in an aquarium which is a very artificial environment. This is something the hobby does not encourage.

At this point, because it is a facet of this hobby that interests me very much, I'll explain what leads to the above. I hope it won't be too confusing.

In taxonomic classification, the species assigned to a genus share several biological, physiological traits. Sometimes but not always there are external patterns that show a close connection, as in the neon lateral line of Parachierodon species, or the "lambchop" black mark on these Trigonostigma rasbora species. But that is only a part of the connection, and sometimes external markings may be much less obvious.

All species in a monophyletic genus are descended from the same common ancestor, or conversely, all descendants of the ancestor fish are present in the genus, and no other species. So there is a very close link between the species, which can most readily be seen in their DNA. Phylogenetic analysis is now being used to establish a more correct representation of the relationships between species. And of course, many species classification (names) will change as a result. Trigonostigma is what we term a monophyletic genus, because it contains four species that all descended from the same common ancestor. These species are more closely related to each other than they are to any other fish in the world.

Many genera are now being determined to be polyphyletic, which means that some of the species in that genus are not as closely related as others because they have descended from very different ancestor fish. As an example, there are well over 150 described species of cory in the genus Corydoras. Phylogenetic analysis by several ichthyologists has now determined that there are in fact nine different lineages which means the genus Corydoras is actually a conglomerate of nine different genera; the species in each of these clades have descended from a common ancestor, one that was different from the other species. The genus Brochis has been placed in Corydoras in order to keep the "Brochis" species together, as there are three or four "Corydoras" that phylogenetically belong with the three "Brochis" species as a distinct lineage from the same ancestor. We still consider all of the species to be "Corydoras" because the work that is needed to fully sort this out will take some time.

And taking this concept of polyphletic further, among a single species there may in fact be two or more distinct species, even though externally they seem identical. For example, the Blackwing Hatchetfish, Carnegiella marthae, which has a very extensive natural geographical range in the northern half of South America. It has now been discovered that there are three distinct lineages within this species. That means that the present "C.marthae" is most likely not one but three distinct species, as the fish descended from three different ancestor fish. Geographical separation can frequently lead to this; it is evolution continuing today as it has since life first appeared.

Byron.

 

[jasong55555]

thanks for the replies! l ended up buying four Trigonostigma hengeli to add to the two i have in my tank