I was always under the assumption that one of the main differences between a true Betta burdigala, and the very similar Betta uberis, is that the latter may or may not have the presence of a lateral spot, while the former will never display one.
Furthermore, on the species profile page for Betta burdigala, Seriouslyfish.com has written this:
In addition it can be differentiated from B. uberis by the following characters: absence of iridescent green mid-lateral body patch in males (vs. of presence, but not always).
I have two pairs of burdigala. One pair is captive-bred, while the other is supposedly wild-caught. None of the fish in either pair display a lateral spot. The only real difference between them, is that the wild-caught pair are much more subdued in their colouration compared to their captive bred counterparts.
Both pairs have spawned. Both pairs have fry, juveniles and sub-adult offspring. Yet in many of these offspring (especially the more brightly coloured young males), I have noticed the development of a lateral spot.
I have read in a couple of places that fish sold as burdigala 'kubu', may actually be Betta uberis instead. However, I have a pair of Betta uberis from Hermanus, and there is marked differences between them and my two pairs of burdigala.
I have noticed that the spot seems to start to fade as the fish ages. I do wonder, if perhaps this is just a concentration of pigmentation that occurs when the juvenile first starts to show the adult colouration. Indeed, with my uberis sub-adults, I can still make out the lateral spot quite clearly, while I cannot on the burdigala of similar age and size.
I did try reading the SeriouslyFish entry on how to distinguish between the two species, but honestly I got lost somewhere between 'pre-dorsal' and 'post-dorsal'.
I am just hoping that what I have is truly Betta burdigala. It would be disappointing to discover that I actually have a different species altogether.
Hailing from Melbourne, Australia, I currently keep and breed a number of species from the coccina complex.