Our cultratus have bred again. It is the first time for 18 months, and is yet another twist in the saga of these peculiar little fish at the CFZ.We first bought them at the livebearers’ auction in Redditch during June 2010. Me, Max and Dave B-P had a jolly day out and came back laden with livebearers. Somehow, through the magic of mobile phones, Dave had also acquired a girlfriend during our 12-odd hours away from base, but that is another story entirely.
As I am sure Max will tell you, I bought the cultratus by accident. I thought they were something else, and when I heard the words livebearer, and £3 in the same sentence I shoved my hands in the air and bought them. They are angular, gun-metal grey little fish that I always think look like miniature porbeagle sharks and they live in a two-foot tank on my desk so that I can commune with them on a daily basis.
They bred for the first time in the autumn of 2010, but just before Christmas disaster struck. There was a power cut and something went wrong with our heater. The temperature plummeted and my nascent colony of cultratus, together with two nannacara cichlids died. I was devastated. Then the two largest female cultratus swam out from a hitherto overlooked hiding place. I was still devastated; even at Christmas virgin births are not something that an aquarist likes to count upon. But it happened. Nine tiny babies, much smaller than the conventionally produced cultratus were soon to be seen in my tank. I nurtured them. Oll made infusoria, I purchased special livebearer feed, and slowly the babies grew. But for the last 18 months they hadn’t bred. I was wondering if – because they appeared to have been produced parthenogenetically. I was beginning to wonder if the babies had been born sterile.
But no. They were just late starters.
Of course parthenogenesis is not the only explanation. I believe the females of some livebearer species can store sperm inside their bodies for some considerable time before choosing to become pregnant. This sounds like the ultimate feminist ideal, and it may be what happened here.
It could be that the female cultratus were pregnant and that the gestation period was far longer than I had imagined. But my personal inference, particularly as the babies were so much smaller than either of the clutches that were born before or since, is that Alfaro cultratus can – under certain circumstances – reproduced parthenogenetically. It would be interesting to find out what the trigger mechanism would be for this. I imagine that there would be some chemical changes to the water when all the male population gets wiped out at once, and this may well be the trigger mechanism. I am presently trying to devise some experiments to test this hypothesis, but without killing off all my precious males. They have been through enough already.
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