Coelacanth

EXTRA LEARNING: Since today's presentations were about fishes and amphibians, I thought I'd share the following documentaries about coelacanths, a "living fossil" that provides a link between fishes and tetrapods. This is the video clip I showed in class: "Finding the Coelocanth" from National Geographic Wild. Here is a longer documentary about the history of scientists' search for these creatures: "Coelacanth: The Fish that Time Forgot." One of my students asked about how these creatures lived and reproduced. What scientists know is that the coelacanth is ovoviviparous (recall what that means) because they have found dead specimen that carried live young within their bodies. The young had yolk sacs attached. These fish are thought to have one of the longest gestation periods among vertebrates--from one to three years! Some neat features that illustrate how ancient these creatures are can be seen in their lobed fins (with arm-like bones!), their hollow notochords, and the peculiar way in which they swim. These fish do not have a backbone at all, but rather a more primitive feature: a hollow notochord. Additionally, their swimming pattern is similar to how tetrapods walk; more accurately speaking, tetrapods evolved their walking pattern from ancient ancestors similar to the coelacanth. The next time you're walking about, notice how your arms and legs move: left leg and right arm move together and right leg and left arm move together. Creatures like the coelacanth were the first to develop that pattern of motion.

Other interesting things related to fishes and amphibians: mudskippers, flying fish, flying rays, axolotl, new species of caecilians, fish vs. fishes.