hybridisation experiments

[blueblue]

I read from the new Datz' book South American Dwarf Cichlids that the
"hybridisation experiments" demonstrate that A. sp. Tefe is a species that should be separated from A. Agassizii, and there are two individal species of fish related to diplotaenia: A. diplotaenia and A. cf. diplotaenia, Orinoco... So, what are these hybridisation experiments about?

 

[Mike Wise]

They refer to the article: Hoffmann & Hoffmann. 1998. Apistogramma sp. "Tefé". DATZ 51(3): 167-170. They showed that crossing the 2 agassizii forms that occur in the Rio Tefé produced spawns in which few fry hatched, the fry were mostly deformed (scales) and were mostly sterile. They recognized that the form close to the Amazon were A. agassizii, but the form from farther up the Tefé was a separate, but closely related form.

I do not know of any reported crossings experiments between A. diplotaenia & A. cf. diplotaenia Orinoco. I imagine it has been tried with results similar to those of A. agassizii & A. sp. Tefé. The 2 diplotaenia-group forms are visibly different from each other in their dark markings.

 

[blueblue]

Thanks much Mike for the illustration. I have one further question:
In terms of the result of the experiment, are there some statistically
significant levels associated with the results? Say, how confident one can claim the result to be true (as it is an experiment, one can state the
hypothesis by a statistical means only)? To be frank, for A. sp. Tefe and A. Agassizii, i myself have bred some and the hybrid (F1) seems to be able to breed among themselves or with other Agassizii... of course, i have no systematic count of the success rate and other details... but i do really want to know more.... do you have a version of the paper/article to share with me?

They refer to the article: Hoffmann & Hoffmann. 1998. Apistogramma sp. "Tefé". DATZ 51(3): 167-170. They showed that crossing the 2 agassizii forms that occur in the Rio Tefé produced spawns in which few fry hatched, the fry were mostly deformed (scales) and were mostly sterile. They recognized that the form close to the Amazon were A. agassizii, but the form from farther up the Tefé was a separate, but closely related form.

I do not know of any reported crossings experiments between A. diplotaenia & A. cf. diplotaenia Orinoco. I imagine it has been tried with results similar to those of A. agassizii & A. sp. Tefé. The 2 diplotaenia-group forms are visibly different from each other in their dark markings.

 

[Mike Wise]

I have the Hoffmann & Hoffmann paper somewhere, but it is in German. I haven't read it in quite a while so I have forgotten if they used any statistical methods. It is a non-scientific paper so it is unlikely that they did. As for your Tefé x agassizii crosses, this was the problem with getting offspring from the original specimens successfully distributed in the hobby. Some found it easy to breed them, other found it almost impossible. Those who found it easy had Tefé pairs; those that found it hard had Tefé x agassizii pairs. Both bred easily & produced fry, but the crosses were not very fertile. Then another form of agassizii was found that many thought was Tefé. It was actually the net form from the lower Amazon that in many ways looks like Tefé. These readily breed with the typical agassizii & their offspring seem to be much more fertile.

 

[blueblue]

Thanks Mike. I see and it is not a refereed scientific paper... then we simply cannot expect the use of rigorous statistical method in the derivation and the presentation of results. Anyhow, it is really an interesting observation ^.^

I have the Hoffmann & Hoffmann paper somewhere, but it is in German. I haven't read it in quite a while so I have forgotten if they used any statistical methods. It is a non-scientific paper so it is unlikely that they did. As for your Tefé x agassizii crosses, this was the problem with getting offspring from the original specimens successfully distributed in the hobby. Some found it easy to breed them, other found it almost impossible. Those who found it easy had Tefé pairs; those that found it hard had Tefé x agassizii pairs. Both bred easily & produced fry, but the crosses were not very fertile. Then another form of agassizii was found that many thought was Tefé. It was actually the net form from the lower Amazon that in many ways looks like Tefé. These readily breed with the typical agassizii & their offspring seem to be much more fertile.