This photo shows a cleared specimen of a pacific moonfish from the California Academy of Sciences in San Francisco. This fish was preserved in a fluid that made the soft tissues more or less transparent, leaving just the bones and a few other structures visible.

Sunfish X-ray

This image is an X-ray of a pumpkinseed sunfish, a freshwater fish that is typically 10-20 cm long.

The X-ray shows the basic layout of the body:

• The swim bladder is a large organ filled with gas (mostly O2); it appears as a light area in the picture. The swim bladder adjusts the fish's buoyancy, so it doesn't sink to the bottom or float to the surface. You can see the ribs on either side of the swim bladder.
• The internal organs, such as the gut and the gonad, are visible as a dark area below the swim bladder. The vent, which is the single opening that serves as both the anus and the urogenital opening, is in front of the anal fin; the back half of the fish is all muscle, bone, and tail.
• The dorsal fin rays are clearly visible. The rays that extend into the upper part of the fin also extend down into the muscles of the fish's back. The fish can use these muscles to raise or lower the fin.