Y. modesta : Caudal peduncle spot

[andyroo]

Any thoughts on this spot?
Sexual dimorphism or dominance trait?
Of my four, the smallest still has, the biggest has beautiful black with light ring and the two middle just have a faded blotch/dark patch.
According to girth, biggest and smallest seem to be female (stouter), middle two male(longer).
How about geography of colours? Some seem more or less purple/black and/or shiny.
A

[Emma Turner]

Hiya Andyroo,

Got any pics of your Y. modestas? Do the two you suspect are females (with the bolder caudal peduncle markings) ever show a faded mark when they are in a certain mood? Were all your Y. modestas bought from the same batch?

I haven't had any juveniles in for a loooong time, but the larger, long term residents (6"+) we have at the shop sometimes show a prominent dark blotch at the the dorsal surface right at the caudal peduncle - but not all the way down the caudal peduncle. The mark at the top is sometimes surrounded by a lighter colour, slightly yellowish if I remember rightly.

Y. lecontei on the other hand, tend to show a much more prominent caudal peduncle mark, pretty much all the time, from what I've observed at the shop (of course this may be different in the home aquarium setting).

Emma

[andyroo]

On the biggest one the spot almost looks like a false-eye: dark with lighter ring. On the rest the spots are faded and without distinct border. Mood-related could well be the control. All came from the same shop and shipment, no guarantees they are related. Smallest is iridescent green and has grown very slowly and rarely schools/interacts with the rest.
Interesting that none of the LOL photos really show this spot, yet i don't remember ever seeing one without.
Will forward photos in the week.
A