Many of you may remember seeing anatomical relief models while at the doctor, dentist, or even in biology class. These are usually models of the heart, brain, head, jaw, arm, etc. that one can hold in your hands and are used to explain anatomical features of a particular body part or biological system. While 2-dimensional pictures are adequate, actually holding a model of something you are trying to learn more about helps picture how things work together.

A 2-dimensional picture of a nematocyst.

Now with the aid of 3D printing, you can print out your own anatomical relief model of a nematocyst. These are great tools for showing students how a nematocyst stings its target. The model on Thingiverse shows a nematocyst in three phases of deployment:

1. Before deployment: the harpoon is packed within its capsule
2. During deployment: the capsule pressurizes, swinging open the operculum (“trap door” holding the harpoon inside), and beginning deployment of the poison-filled thread
3. After deployment: the poison-filled thread is deployed and embedded in the target that brushed up against the nematocyst.

These models are excellent for those of us that talk to students about coral anatomy and make fantastic visual aids for better understanding how cnidarians use nematocysts to feed and defend themselves from predators. A big “Thank you!” to Daniel Newman from the Natural Science Illustration program at the Rhode Island School of Design and Casey Dunn for making the model available on Thingiverse.