Biotoecus id please

[Gamelle]

Hi,

I just got 5 specimens of wild caught Biotoecus, could you please tell me if they are opercularis or dicentrarchus .... in fact, I'm a bit lost because I didn't catch the difference between both ... one is suppose to have only 2 spines on the anal fin, but the other could fit both 2 or 3 spines ...

What about the adult size of both species ?

If necessary, full size photo is available here :

Thanks in advance

--
Stephane

 

[jose_vogel]

For me is B. dicentrarchus.


The body of B. dicentrarchus is more elongated than of the B. opercularis; besides, B. dicentrarchus has a dark chin.

 

[Lolojil]

Hello,

There are 3 anal spines on this fish and to me is an opercularis form (opercularis, cf opercularis ? ).

Julien

 

[Mike Wise]

I agree with Lolojil, there are 3 anal spines. The dorsal edge of the caudal peduncle (at the end of the dorsal fin) shows a slight downward "notch" which is a characteristic of B. opercularis. B. sp. aff. opercularis has a more even dorsal line. Do you know from which river system your fish were collected?

 

[jose_vogel]

OK, if Mike (and Lolojil) agreed that it´s an opercularis, it must be opercularis.


But, Mike, what´s about the "black chin". I read (on Römer´s) that it´s a characteristic of B. dicentrarchus.

 

[Gamelle]

Thanks all for your answers

Mike, as far as I know, the specimens have been collected form Rio Negro River system, more precisely in the area of Caicubi.

 

[Mike Wise]

Thanks all for your answers

Mike, as far as I know, the specimens have been collected form Rio Negro River system, more precisely in the area of Caicubi.

Only B. opercularis is found in this area, in the lower/middle Rio Negro.

 

[Mike Wise]

But, Mike, what´s about the "black chin". I read (on Römer´s) that it´s a characteristic of B. dicentrarchus.

Actually, the cheek patch is seen on all of the species. B. dicentrarchus is separated from the other species by the following:

fewer soft dorsal rays (7 instead of 8)
longer front dorsal fin rays on adult males
shorter caudal peduncle
usually 2 anal spines.

As much as I respect all of the work Dr. Römer has done with dwarf cichlids, I feel that he does not have a "taxonomist's eye" for seeing many of the subtle features that separate species. Therefore I tend to look very critically at his diagnostic features, often needing to ignore them as poorly defined.

BTW, the fish that Römer pictures in CA1, p. 1005 as B. cf. dicentrarchus is actually a 2-spine specimen of B. sp. aff. operuclaris.

 

[Charly EON]

Hello

Thanks Mike for your detailed answer. Do you have a picture of B. dicentrarchus so that we can clearly see the difference ?

Do you think B. opercularis Tapajos (as seen in Buntbarsche amerikas Band 3 page 73) is the same species as the fish pictured by Gamelle ??

Thanks n advance for your reply

 

[jose_vogel]

Mike, thanks for your explanation.

BTW, the picture you mentioned (Römer´s CA1, page 1005) is the one I used to identify Gamelle´s fish.

 

[Mike Wise]

Hello

Thanks Mike for your detailed answer. Do you have a picture of B. dicentrarchus so that we can clearly see the difference ?

Do you think B. opercularis Tapajos (as seen in Buntbarsche amerikas Band 3 page 73) is the same species as the fish pictured by Gamelle ??

Thanks n advance for your reply

Yes, it seems that the Biotoecus specimens from the lower Amazon [Rio Trombetas to the Rio Branco (Rio Negro system)] are all very similar to the type B. opercularis from the Lago Saraca, near Manaus. This includes those from the Rio Tapajós. I have never seen photos of specimens from the upper Rio Madeira (Lagoa Abunã), so I can't comment on them.

 

[Fabien]

Some pics of my Biotoecus : same shipment of Gamelle's Biotoecus.

They come from middle Rio Negro drainage (Caïcubi). With hindsight, the thinness of the body and their origin make my thinking of B. aff. opercularis middle and upper Rio Negro.

 

[Gillie]

Actually, the cheek patch is seen on all of the species. B. dicentrarchus is separated from the other species by the following:

fewer soft dorsal rays (7 instead of 8)
longer front dorsal fin rays on adult males
shorter caudal peduncle
usually 2 anal spines.

As much as I respect all of the work Dr. Römer has done with dwarf cichlids, I feel that he does not have a "taxonomist's eye" for seeing many of the subtle features that separate species. Therefore I tend to look very critically at his diagnostic features, often needing to ignore them as poorly defined.

BTW, the fish that Römer pictures in CA1, p. 1005 as B. cf. dicentrarchus is actually a 2-spine specimen of B. sp. aff. operuclaris.

This detailed description is going to help me alot Mike. I am going to try for better photos for you tonight now that I have the time and a better camera. Even if my fish doesn't match the description 100% I'll send photos just in case.