Is it normal for some fishes to have "curved" spines?

[fanyfin]

I see so many fish (both online and in-person) that have bent or curved spines.

For example, for different types of tetras, I can see many pictures where they have curved spines. You can do a image search for, say, candy cane tetra or red phantom tetra or x-ray tetra and you will see what I mean.
I have also put some links below to images showing the curved spines.

Is it normal for fish to have curved spines? (whereas others do not - even for the same species as you can see from pictures online)

Or is this a sign of a disease like fish "tb" (Mycobacterium) which is more prevalent than we think?

Thanks.

----------------------------------------

BELOW - Pictures of fish with curved spines
(some of these are even from online fish stores!)

https://preview.redd.it/sovudwlwkqw21.jpg?width=960&crop=smart&auto=webp&863896b5
https://www.liveaquaria.com/images/categories/large/lg_102775_Candy_Cane_Tetra.jpg
https://4.bp.blogspot.com/-ZkwW6STh...AAAE78/VmQwrNC3thI/s1600/x-ray-tetra-fish.jpg

https://cdn.shopify.com/s/files/1/1163/2672/products/X-Ray-Tetra-Small-8_1024x1024.jpg
https://cdn.shopify.com/s/files/1/1163/2672/products/Candy_Cane_HY511_Tetra_3-b_1024x1024.jpg
https://cdn.shopify.com/s/files/1/1...den-Blue-Emperor-Tetra-Small-_7_1024x1024.jpg
https://cdn.shopify.com/s/files/1/1163/2672/products/Black-Phantom-Tetra-9_1024x1024.jpg

----------------------------------------