# I'm confused



## PygoManiac (Jul 26, 2004)

I've read that female Nattereri look identical to males. But then I've also read posts and seen pics of members showing pics of eggbound female RBs which look distinctively plump(without them being overfed or anything) compared to males. IS it that female RBs bigger than 7" are thicker and fatter than males? Or is it that they get eggbound after pairing up with a mate?

By the way I came across x-d-x's pic gallery, those RBP pair and fry pictures seemed awesome, incase anyone hasnt noticed:

http://www.piranha-fury.com/photopost/show...user=26&cat=500


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## jmcrabb (Oct 3, 2003)

nats are not sexually diamorphic... that is, you can't tell male from female until they are actually spawning...


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## hastatus (Jan 16, 2003)

Females P. nattereri always carry eggs, they expell them from time to time to keep from imploding (internal rupture of sac). As stated above they are not sexually dimorphic. I have seen many, many piranas purported to be females and when examined via dissection, they were males. Just very fat creating this false positive for sexuality. Included in this misinformation of viewing such fish as female or male is the thickness or length of the anal fin first ray. Again, this is not a diagnostic tool to confirm sexual dimorphism of the species.

So the bottom line is this, if you see your fish lay eggs, then YOU can ID this one fish as a female. The other fish that might engage with the "female" may also be a female too. One never knows for certain until eggs hatch and are fertilized. The more piranas you have in the tank, the harder it will be to distinquish which is which once eggs are laid. Again, you will be able to tell from YOUR FISH which is female once this process begins.


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## PygoManiac (Jul 26, 2004)

Thats cleared up my mind. I had read in Nike's article that Natts are sexually non dimorphic, but then again some people posted pics of 'eggbound females'. Thanks Frank.


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## hastatus (Jan 16, 2003)

> PygoManiac Posted on Aug 6 2004, 12:26 AM
> Thats cleared up my mind. I had read in Nike's article that Natts are sexually non dimorphic, but then again some people posted pics of 'eggbound females'. Thanks Frank.


That is very true, some of the "egg bound females" were sent to me by other hobbyists and once I cut them open, the fishes testes were present (male). What happened in some cases, the bloated belly was the beginning of the end of a disease/parasite problem. The only sexually dimorphic pirana verified by science is Pygopristis denticulata. There might be some Pristobrycon that are as well, but have not been officially recognized yet. On Pygopristis, the anal fin is bilobed (male).


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