I am loath to pop this thread back to the top but it got me thinking of post-working a sphincter for an alien artifact... say a memory device or analysis device.

Here was my first shot at it...

In UVmaper I made a ball prop and screen captured it.

In Photoshop I copied the layer and set it to luminosity mode so the dodge and burn tools wouldn't shift the colors.  On this duplicate layer I drew an "asterisk" shape "*" with the burn tool and filled in the intersections with the dodge tool. Then I smoothed things a bit with the smudge tool trying to get a rounded look at the intersections.

I made a copy of this layer and used the Liquid Tool to dilate the sphincter.

I painted a probe or energy wand typ thing on a new layer over that and went back to the layer with the dilated sphincter and burned with a large soft brush to kind of push the sphincter in then smudged that around to kind of meet the wand shape. Then I merged those two layers and used the blur tool where the wand enters the sphincter port.

This is three minutes works so it is rough but it is a proof of concept I guess. Photo references of some actual sphincters and wand shapes would probably help a lot but this does show how burn and dodge on a luminosity layer can sculpt the surface of the volume to create the appearance of an orifice. I thought the concept might be sound based on experience painting clothes this way back at the turn of the century. With clothes you can paint a separate color or hue layer of the burn/dodge/smudge layer to distinguish the clothes from the figure.

A prop anus might be a good starting point for burn/dodge/smudge like this but probably a simple torus would do since in the end any solution would probably require post work.

Nudity tag is in case some one interprets my alien artifact and data probe as a organic life form of some sort in a unclothed state.