Is it normal for some axies to have smaller gills ?

[k]

I noticed that some of the axies in the pet shop had pretty small gills - can this be just a genetic thing or does it (always) indicate illness ? They seemed pretty healthy apart from that ... what size is normal (proprtionately) ? Thanks

 

[joan]

Genetics, they could have been bitten off, illness, or the water has a high oxygen content. There isn't really a 'normal' length.