As I've mentioned in this blog previously, my group of Betta sp. cf. rutilans green have suffered from recurrent bouts of oodinium (velvet) in previous years, the last of which I believe I was successfully able to eradicate after several weeks of treatment. Unfortunately, this put any breeding plans I had for the group on indefinite hold as I was afraid that the parasite might still be lingering in the gill tissue of the adult fish, and the presence of fry may be enough to trigger another attack.
However, after finding one of my males mouthbrooding in the main tank recently, I decided to remove a pair to a smaller breeding tank (about 12L) and see what happened. This species has always intrigued me, not only because they have never been officially described, but also because they utilise such an unusual reproductive method (for fish from this complex).
It took my pair a few days to settle into the new tank and start showing an interest in spawning. However, my patience was soon rewarded, when I found the two of them wrapping in a film canister. Like my previous breeding efforts with this species, the male did not build a nest, but instead chose to incubate the eggs in his mouth. Based on previous experience, I knew it would be two or three days before I saw any fry.
Well yesterday, my male spat out a mouthful of fry. They still had their yolk sacs attached, and at present, are gathered inside the film canister under the watchful eye of the male. I thought perhaps he had built a bubblenest to contain them, but on closer inspection this proved not to be the case.
I don't know why it is that Betta sp. cf. rutilans green males show a proclivity for mouthbrooding. Are these specific environmental factors that trigger this behaviour, or is it simply a way to better protect vulnerable eggs from predation? I have seen photos of other males from this species mouthbrooding, and in 'The Betta Handbook', the author does make mention of it, so it seems that this is a normal and instinctive behaviour for males.
Even more curious, is the fact that the mouthbrooding period for Betta sp. cf. rutilans green is so brief compared to that of recognised mouthbrooding species. Fry are released in a matter of days rather than weeks. Normally the fry from mouthbrooding species are fully developed upon release, but my Betta sp. cf. rutilans green fry (both past and present) are often not even fully free-swimming.
I suppose that until someone does a study on moutbrooding in both Betta sp. cf. rutilans green and Betta brownorum, all we really have is speculation.
Hailing from Melbourne, Australia, I currently keep and breed a number of species from the coccina complex.