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Fry from Phallichthys quadripunctatus at around half their normal size.

Home Forums Fresh and Brackish Water Fishes Fry from Phallichthys quadripunctatus at around half their normal size.

This topic contains 0 replies, has 1 voice, and was last updated by  Matt 3 years, 3 months ago.

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  • #303297

    plesner
    Participant

    I’ve kept Phallichthys quadripunctatus, the Four-spotted merry widow, for quite a while. They breed like clockwork every 4 weeks at 26°C and usually produce 15-20 fry at around 5-6 mm – very similar in size to guppy fry.

     

    6-7 weeks ago I put two adult pairs into a very densely planted 140L tank with some orange cherry shrimp and some young red ancistrus. Since then, they’ve dropped 3 broods, all of which were as expected. The 4th brood however, took me by surprise. It seems that all the fry (or at least the vast majority – it’s difficult to be 100% sure due to the dense vegetation) are only around 3 mm long – about the same size as fry from Heterandria formosa, Least Killifish, are when born. The smaller fry seem to be doing well, eating and swimming around like the normal sized fry.

     

    I did change one thing a couple of weeks ago. I discovered a few hydra in the tank and upon reading about them, I’ve changed from feeding live foods to dry foods only in that tank, as I try to get rid of the hydra by starving them. They apparently only eat live organisms. Starving them seems to be working as I haven’t seen any hydra for several days, but I’ll be using dry foods for at least another 6-8 weeks, just to make sure.

     

    Has anyone in here ever heard of something similar – perhaps in other livebearer species? Could the change in diet influence the size of the fry while they’re still developing inside their mother?

    #353220

    Matt
    Keymaster

    Hi Karsten, it does looks like this has been observed in some other poecillids. Check here and here.

    #353225

    plesner
    Participant

    @matt said:
    Hi Karsten, it does looks like this has been observed in some other poecillids. Check here and here.

    Thanks a lot Matt. I’ve read the first one, but the 2nd one requires a login.

     

    Well, it seems that my Phallichthys quadripunctatus do behave in a similar way to some of those mentioned in the first paper. What I find interesting is that a change from live foods (microworms, freshly hatched artemia and sieved Daphia pulex) to good quality dry foods had such an impact in just a couple of weeks.

    #353230

    Matt
    Keymaster

    Yes it is interesting for sure – perhaps this is natural plasticity which may also explain its success as an invader? Smaller fry should require less energy investment when resources are scarce.

    I’ll send the other paper over now.

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