Animals > Chordates > Bony Fish
This page shows a few extra images of bony fish. For more complete anatomical diagrams, see your lab manual. Before dissecting a fish, you might want to use the pictures on this page to give yourself an idea of the overall anatomical layout.
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.
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.
Most of the information for today's dissection is in the lab manual. The fish are called beltfish in the grocery store, but they go by other names as well. They're in the family Trichiuridae, but I'm not sure which species. I think they might be Trichiurus lepturus or Lepidopus caudatus.
Miscellaneous beltfish links:
- Scabbard fish at Mercator mud volcano (YouTube). A video of these fish in their natural habitat.
- How to preserve a beltfish skull on Taxidermy.net (The author of that post also has a collection of bone photos on Flickr.) In case you want to know how to preserve fish skulls (it doesn't look easy).
Fish Anatomy Links:
- Fish Dissection Guide (pdf; from Queensland Academies)
- Fish Anatomy (Wikipedia)
- Striped Bass from Jared Travnicek, a scientific illustrator
Otoliths are small calcified structures inside the inner ear; they aid in balance. Otoliths grow by adding a new layer each year, a little like tree rings, and they can be used to determine the age of fish. Can we find the otoliths in our beltfish? I don't know, but if you want to try, you might look at these links:
- Online Otolith Lab (University of Alaska)
- Introduction to Aging Fish: What Are Otoliths? (Florida Fish and Wildlife Conservation Commission)
- Removing fish otoliths (YouTube)
- How to Remove an Otolith (Bedford Institute of Oceanography)
- Otolith Removal and Preparation for Microstructural Examination: A Users Manual (1991) by D.H. Secor, J.M. Dean, and E.H. Laban. Very detailed!
This page updated November 19, 2013