Differences between orange stripe and copper cardinals?

[pookstreet]

Does anyone know what the major difference between Apogon cyanosoma (Orange Stripe) and A. margaritophorus (Copper) Cardinalfish?

I have a group of 10 what I presumed were A. cyanosoma. They all had varying degrees of orange colored stripes when I got them a few months ago. However, about a month or so ago, I noticed that only one has the orange colored stripes now and it's by far the biggest of the group, approximately 50% bigger than the rest. My initial reaction was that it has become the dominant male. But what got me was that the stripes on the remaining fish have changed color somewhat and not bright orange anymore. Is this simply sexual dimorphism or something else altogether? Here are some photos if that helps.

The big boy.....

The others.....

Part of the group together.........

 

[Elysia]

They all look like A. margaritophorus to me. You can tell from the little spots on their sides.

 

[pookstreet]

Good call, Elysia! I hadn't paid attention to the patterns, just the coloration. Now I wonder if the lone bright colored one is the male. It's interesting that the rest dulled in coloration with time.

 

[Sardaukar]

Ya other than the color, they have identical patterns and what not. Must be the same species.

 

[Elysia]

I've read that females can be larger than males in some cardinalfish species. I guess this could be because the males orally incubate the eggs, and thus they don't eat at that time. If they were large, that would just be more body to try to keep going on little to no resources. I don't know, that is just a guess.
So, the only way that I know to gauge the sexes is by the jaws -- the males sometimes have larger jaws to handle those egg masses. I guess that is the reason why these fish can take in suprising large pieces of food!

 

[AquaKnight]

Agreed that those are A. margaritophorus. As Apogon cyanosoma get larger, their stripes get thinner. Here was our Orange Stripe that was decent sized, 2" or so.

 

[pookstreet]

I guess we'll all find out if someday they ever start breeding in my tank.........lol.


Great pic of a cyanosoma, AquaKnight! Thanks for the confirmation.