How to Stretch a Squid
Sometimes Humboldt squid are so abundant that hobby fishermen catch more than they want to keep. One of the motivations behind the Squids4Kids program was to make use of these otherwise wasted deaths by asking the fishermen to donate their excess catch to classroom education. If a Humboldt squid dissection inspires a group of students to be excited about biology, to learn about the natural world around them, then it has served a good purpose.
The more students a single squid can serve, the better--especially during times when Humboldt squid are less abundant, and Squids4Kids specimens are limited. Based on our own experiences serving multiple classes or groups with a single squid, we've come up with this short guide to "stretching your squid."
The most important thing to remember is to take care in the dissection. Avoid puncturing any internal organs, especially the stomach, liver, and ink sac, as these will ooze fluids that obscure the rest of the anatomy.
Only the first group will get the excitement of watching the mantle cut open with a knife, but it is not difficult to replicate this experience with later groups. After the first group is finished, close the mantle by drawing the cut edges together and gently roll the body over so the cut is facing down and the weight of the squid holds it closed. The squid should look almost the same as it did before the dissection. Subsequent groups can observe the external anatomy of the squid, from fins to tentacles, just as the first group did, before you roll the body over and open it up again to look at the internal anatomy.
If all groups are observing the squid over the course of a single day, there's no need to be concerned about decomposition, unless it is very hot. If you want the squid to last over more than one day, keep it cold between uses. Refrigeration or regular ice in a cooler is best, so that the squid doesn't become completely frozen, but if you want to keep it for a long time or don't have any other options, freezing or dry ice may be used.
It is best to leave the head intact until the last group. The squid may be looking (and smelling) a little bit tired by this point, so you can make the dissection more exciting by opening the head. A cut just under the siphon will expose the braincase. The eyes can be opened to look at the liquid pigment inside and the structure of the lens.
We hope this guide helps you to serve the most students with a single squid!