Pollimyrus isidori are great fathers

We’ve been trying to breed Pollimyrus isidori in the lab for the last couple of months, which are well reputed good parents .  Withstanding some pH problems that we have been having over the past months, we’ve finally witnessed the fruits of our labor.  As of another big clutch of eggs this morning, we have more than 200 individuals!

[youtube https://www.youtube.com/watch?v=VdG9dhmgovI]

To my surprise, the 50 or so individual fry we found yesterday afternoon all seemed to be hanging out near their dad– certainly not a random distribution.  Watching dad for a few minutes revealed a very interesting behavior– whenever a fry (which at this early stage are quite pathetic swimmers) managed to get away from the nest, Dad would come by and scoop him it up in his mouth.  Initially, I thought that he was eating the eggs, but then I witnessed that after a minute or so, he would swim back to his nest and spit it back out!  Armed with my iPhone, I got some video of the pickup behavior.  Most of the time, he put the eggs where I couldn’t video record, so the video represents the pickup of one egg and the dropoff of another:

[youtube https://www.youtube.com/watch?v=ymqo0UnqpYw]

This morning, Monica and I found many more fresh eggs– we took them up to count, and then returned a portion to the tank in a petri dish to see what the father would do– about 50 all told.  We left the lights off for about 2 hours, and when I came back, all of the eggs were tucked safely back in the nest!  Truly impressive behavior!


Posted in In the Lab
3 comments on “Pollimyrus isidori are great fathers
  1. How big is the tank? How old are the parents? What are you feeding the parents? How did you select the pair? Did you distinguish the sexes by electrical patterns?

    • jasongallant says:

      Hi Anthony,

      The parents are easy to sex due to what is called an “anal fin reflex” present in some mormyrids. If you drag a pencil (or your finger) along the anal fin, males will reflexively “cup” their anal fin in response to stimulus. This is how we determined the male. Juveniles and females will not do this– females tend to be “deeper bodied” and lack a distinctive notch in the part of the body where the anal fin inserts. The tank is 1/2 of a 125 standard 125 gallon tank– this should work in a 50 or 75 gallon tank, no problem, provided there are good “hiding places” and lots of plants for the males to build their nests, etc. We are not sure how old the parents are, as we obtained them from the pet shop– the size of the male is only a few inches in length. Odds are that the ones you would find in a typical pet shop should be the right age. We are still learning as we go, but there is some literature out there on this!

      Jason Gallant

  2. Sara says:

    thanks for this post

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