Originally Posted by rlederer
It is a gonopodium, a modified anal fin, that the male livebearer uses to deposit packets of sperm into the genitalium of the female. A livebearer fish version of a penis, yes.
Yes, that's the term. And I forgot the term, anal fin.
The reason why I ask is because a month and a half ago, I added 2 female and one male platy to my aquarium, and sadly the females died in a week thereafter. My male platy was swimming and thriving in my tank of mollys while being the only one of his kind. Then three days ago he became lethargic, inactive, just sitting on the bottom or hiding. I thought he was a goner. But prior to that, I saw him trying to 'mate' with the mollys who of course ignored him. That's when I notice him extending his anal fin left and right as he was swimming around. Because I just feared he was going to die, I thought let me run out and get a female platy. I did just that yesterday evening, and would you believe by morning, he was up and swimming lively again, and eating again as well. I was so relieved. But I hope this female platy survives. Those who are familiar with my previous posts, I started this hobby this past summer with guppies and I was very upset at how quickly they die because of their overbreeding. I decided to stick to mollys and I'm very happy. The reason for my platy was because back in early November, I took advantage of the guppy/platy sale at the pet store (buy 6 get 2 free offer) and that was my last guppy/platy investment. Needless to say, I have 3 guppy fry, almost 3 months old, and currently thriving. Let's see what happens.