Assetbundles take a lot of memory on device

I download asset bundles (containing transparent textures) from a server.

They have 18mb on the server.

After downloading them, the uses 140mb for data.

What is happening here?
Is there a way to advoid this.

I assume thats 140MB in memory.

What is happening is that they are being decompressed and MipMapped so they can be used to render from.

Reduce the size of your textures and/or the MipMap levels.