Introduction: Lobster Dissection

Hooray for lobsters! Giant sea bugs! This is made for biology teachers in a pinch, or aspiring anatomists just coming out of their shell. Lobsters are not only a highly prized seafood, but they're an incredible family of organisms, too. They molt, they can grow back eyes and claws, they don't seem to age, they're everywhere, they're fastest backwards, and they can get up to 40 pounds. For an amazing look into arthropods and marine life, look no further than your friend Pinchy.

  • What: Lobster Dissection
  • Time: varies, ~30-45 minutes is good
  • Materials:
    • Lobster (note blow)
  • Tools:
    • Utility knife
    • Tweezers
    • Gloves (optional)
    • Tray (optional)

A NOTE ON DISSECTION:

Dissecting animal organisms is a tricky subject which ultimately some will object to and that's okay. For me, I believe that with careful scientific exploration of animals who were treated in humane ways, we can learn and teach our students to be greater stewards of the environment, and especially toward the species they just learned about. There will always be some students who wish not to do a dissection, and we always allow whatever level of participation they choose in these experiences. Many prefer to just watch. Many of those eventually join in. But whatever it is, feel it out with your classroom or audience.

A NOTE ON LOBSTERS:
An interesting thing about lobsters is that they're often sold live. This means that it is often up to the chef (in normal cases) or the scientist to kill the lobster themselves. Because of this, there has been great debate over the best and most humane ways to do this are. Some argue that lobsters can't feel pain, others say they can. A great synthesis can be found in this article. As a science teacher, I prefer finding ones that have passed away at the grocery store, which are available. If you have to work with a live lobster, packing the lobster in ice several hours before the dissection works to humanely kill the lobster, or you can put it in a tub of ice-cold water and salt slurry as according to the humane society. This is part of what is involved in the cooking process, too, so it is nothing excessive, and is part of eating meat. Lobsters just bring it closer to home.

Okay, lobster time!

Step 1: Claws (Chelipeds)

Starting with the external anatomy, the most striking part of a lobster are the claws (also called Chelipeds). These are the first pair of legs, and different from the rest, because, well, they're giant intimidating claws.

What's neat is the claws develop differently from each other and one becomes the pincher claw and the other the crusher claw. These also seem like great names for members of a metal band. The crusher claw has more girth and has large "teeth" made of calcium that help with breaking shells, and well, crushing. The pincher claw (or cutter claw) is thinner and more docile, made for cutting flesh and striking quickly. Another nifty thing is that if they lose one, they can grow them back the next time they molt.

If you're working with students, you can ask them which they think is which, and you can test their range of motion. Open and close them, and move the whole leg around to see their range and amazing mechanics of their claw joints.

Step 2: Eyes, Antennae, and Mouth

Here's the pretty lobster face that only a mother arthropod could love (or a budding biologist!)

The largest features are the three pairs of antennas, a large pair and two smaller pairs. The large antennas are used for touching, and navigating their way around. Lobsters have poor eyesight, so these function as a good pair of canes for getting around, especially since they often hunt at night. The smaller two pairs of antennas are more flexible and sensitive to chemical signals in the water, such as smelling food. Just above these you'll find the hard rostrum, which though it looks like a nose, serves only to protect the lobster's eyes.

Lobsters have two eyes like us, and do not really see clear images. However, they are very good at sensing dark and light, including shadows in low-light situations. The eye has a reflective layer covering a convex retina, which is super neat. Our retina is concave, like a satellite dish receiving light information from our lens. Their retina is like the outside of a dome, taking light in from all sides. WILD.

Lobster mouths are composed of mandibles (jaw-like parts) and maxipilleds (for bringing food to mouth). If they appear as some nightmare-ish alien death trap, you're not wrong, just perceptive. It's scary in there for small animals, and the scariest part perhaps is that the chomping even continues when you get to the stomach. More on that to come!

Step 3: Legs Legs Legs

Lobsters have legs for days.

Moving from front to back, after the claws we continue with four pairs of walking legs (pereiopods). The first two pairs also have claws on them used for eating, and the back two are pure walkers. This means they can eat with their feet! Neat! You can move these around to see their wide range of motion.

Behind the walkers are the gonopods, which are the easiest way to tell if a lobster is female or male from the outside. In males, gonopods are larger, white, and rigid. They are used for holding on to females during mating, which happens usually right after the female has molted. In females, they are smaller, and used to carry and ventilate eggs.

Behind those are an array of five pairs of swimmerets (pleopods). They look like fins and are used to help with swimming, and move in a beautiful flowing motion if you get to see lobsters in the wild.

Probe each of the legs and articulate them to see their range of motion.

Step 4: The Tail

The abdomen is also known as the lobster tail. It is comprised of six segments, and articulates beautifully. At the back of it, the tail can spread out with parts called uropods and the central telson when needed, and shrink back quickly like a fan. Also, the entire tail can curl up toward the walking legs and uncurl rapidly to help the lobster swim backwards quickly when the lobster needs to flee.

Try articulating both of these motions to test out the leg mechanics.

Step 5: First Cut: the Stomach(s)

Our first cut into the lobster is on the dorsal side on its "back," just behind its eyes. Using a utility knife and a good amount of force, you can cut out a window in the lobster's shell. They're tough!

Remove the plate, and you should be able to see the lobster's two stomachs, the cardiac stomach (closer to eyes), and the pyloric stomach (right after the first). Probe the cardiac stomach, and you can feel something hard within. If you reach in with tweezers, you can pull out its stomach teeth! EEEP! It keeps chewing even in its tummy! You can see these in the photos, but are much stranger to feel in real life.

If you're lucky, you might be able to see the lobster's brain, but it is difficult to find as it is smaller than a pea, and somewhat dark in color. It is just behind the eyes.

Step 6: Second Cut: the Gills

Next up, we're going to use the utility knife to take out a side panel of the lobster's cephalothorax.

Inside, you will be able to see the feathery array of gills. They're beautiful. If you take them out, you can see just how much surface area they have as they are made of many wispy strands packed together. This is optimized for pulling oxygen out of the saltwater it lives in. If you have a microscope, use it for gills. They look incredible.

If you peel back the gills, you can see more a defined exoskeleton (in addition to its shell) that helps give the lobster's insides structure and protection.

Step 7: Third Cut: the Tomalley

Next up, remove more of the top part of the cephalothorax to reveal the tomalley. This is a huge green digestive organ that takes up a large part of the lobster's insides. It fulfills the role of both a liver and a pancreas. It is also called "lobster paste," and is often considered a delicacy. In some places, it can have too high level of toxins to ingest, so check your local FDA listing.

Step 8: The Heart

At the base of the cephalothorax, you will find the heart. It is located right near the dorsal side of the lobster's shell, is a light pinkish, and is amazing. In my case, the lobster had been dead for more than an hour, and the central nervous system disconnected. And still, the heart was still contracting even post-mortem. Look at that first picture. It's actually a GIF.

It's an intense experience, and be quite a moment for a lot of students. It is also a launching point for discussing what the definition of being alive is. If you want, you can have students place their finger on it to feel. Later, when they remove their gloves, you can have them find their own heartbeat as well. I assure you, the lobster is not by traditional means alive even though the heart is still pumping as the nervous system and surrounding ganglion have been detached and inactive for some time.

Often, students will ask about blood, which has actually been all around. Lobster blood is colorless and transparent. It becomes bluish when it comes into contact with oxygen due to the presence of hemocyanin which contains copper.

Step 9: Fourth Cut: the Tail

The next cut is on the dorsal side of the tail, cutting down along the top of it.

When you open the panels up, you can clearly see a white line running the length of the lobster on top of the tomalley. This is the intestine, which will ultimately end up at the anus. Just like us!

Spread across the tomalley in males, you can see two lines which each end with long clear-ish sacs. These are the testes, and the home of sperm production. In females, you can see ovaries, which can appear as a long red line. Sometimes, you can even find lobster roe (lobster eggs).

Step 10: Fifth Cut: the Legs

An amazing feature of lobsters and all arthropods are the way their legs work. They are extremely flexible, and involve an amazing network of of muscles attached to their shell and help from fluid pressure from their hemolymph system. This part is similar to, but not as drastic as the amazing hydraulic leg motion of spiders.

This makes it so that will some pushing and pulling and pressure applied in the right areas, you can make claws open and close with a pair of tweezers. Try it out to see what happens. As you dissect the legs, you will also find translucent stiff parts of the exoskeleton made of chitin, which is found in all arthropod shells. Looking at the claw, you can even find tissue where you can see the site of calcification where new "teeth" of the claw are being formed.

To everyone a claw!

Step 11: Keep Exploring

Hooray! You did it!

And don't let me stop you there, there are more parts of the lobster to be seen. You can look at the inside of the eye or the structure of the lobster's face. Take a look at what the lobster ate, or grab some parts and head to the microscope. There is so much more to learn.

Or to cook! There are a hefty load of recipes and how-to instructions online, and then you can create a no-waste dissection and have participants get a snack, too! This also is great and bringing the human and nature relationship aspect home as well.

For more lobster information, I would recommend anything from the Lobster Institute of Maine, but also St. Lawrence for anatomy, and this fun video for lobster facts.

I'm excited to see what you learn and find. Feel encouraged to write with comments and questions below!

Have fun, and as always, keep exploring. :)

Comments

author
Crandlemire made it! (author)2015-11-01

I've enjoyed Instructables for years but I don't have to post a "nice comment" just because they want everyone to feel warm and fuzzy. This instructable served no purpose other than to be cruel and gruesome and I guarantee that if this were a kitten or puppy dog people wouldn't be saying how educational this really was.

It was sick and should be removed from instructables.

author

Hi there, Crandlemire!

I must have missed a previous comment, and I'm so sorry this 'ible rubs you the wrong way. I completely understand. This was published primarily for science teachers who teach anatomy through dissection as a means for understanding zoology. It is part of a consistent practice in medicine, veterinarian schools, and biological education. In this particular case, too, I made sure to take careful precautions with handling and ethical practices that are consistent with what people use in cooking and what PETA and the Humane Society recommend. Everybody has their different limits with these matters, and I completely emphathize that this crossed yours.

Very happy to discuss this further as it is important to continue discussing ethical practices, so feel to message me for more.

author
jay15136 made it! (author)2015-10-31

Before any comment is made, Instructable clearly states:

We have a be nice comment policy. Please be positive and constructive.

Your comment is neither.

I personally found this instructable to be incredibly well done and very informative. Shocking, yes, to come to Instrucables and seeing something so vastly different from the norm. However Just because something is different does not give anyone the right to start name calling.

To the Oakland Toy Lab - thank you for a educational Instructable. I found it to be very interesting and educational. Having ate my fair share of lobsters, it was very cool to see how they 'tick. Great Instructable!!!

author
GarrettC made it! (author)2015-10-31

"I assure you, the lobster is not by traditional means alive even though the heart is still pumping as the nervous system and surrounding ganglion have been detached and inactive for some time"

author
Cody_LH made it! (author)2015-10-30

Awesome! Not going to do it myself but looking at everything was cool. Just thought I would add that I have eaten a lobster eye before and they aren't bad.

author
Jobar007 made it! (author)2015-10-30

Super awesome. I looked at the picture of the heart and said to myself, "That looks like a gif because it is moving slightly." And then the heart beat. Wow! Life is incredible!

Thank you so much for this. It was really informative and the humor at the beginning was great.

author
samalert made it! (author)2015-10-30

Amazing pics ! Those are amazing species, being a fauna lover i find this somewhat disturbing, but it was very informative and in depth.

author
HBomb187 made it! (author)2015-10-29

I really found this to be very interesting, and thank you so much for sharing this with the community! Also now I know where a lobster's anus is...so...that's interesting!

author

You never know what's going to stick with someone. :)

author
Unirox made it! (author)2015-10-28

thats awful and has nothing to do with technics

author

Hey Unirox! Thanks for the comment and sorry that dissections don't sit well with you. It's a tricky thing category-wise since "Science" is a subheading under "Technology" and so things populate there. Hopefully there will be a biology tab someday, and that understanding anatomy can help us in being better stewards of the environment we live in.

author
Treasure Tabby made it! (author)Treasure Tabby2015-10-28

Hope the poor guy was at least frozen. Bugs have feelings too. :(

author
ThePrintPlace made it! (author)2015-10-29

This is an excellent instructable. Thank you. I'm going to do one if i can get hold of a lobster.

I was bothered by the beating heart though... Does your method of cooling the lobster down not just make it hypothermic rather than dead? How do you know your lobster is dead (which I assume to be a cessation of nervous activity)- or is it just that the heart muscle is still contracting because of spontaneous depolarisation of the cells? (how come they don't stop when they run out of oxygen though?)

Lots of questions cos I found that bit really disturbing- I don't want to cut up a living thing.Can you explain please?

author

Hi, ThePrintPlace! Thank you for the comment, and yes, the heart is still contracting long after the shutdown of the central nervous system of the lobster. The best way is to simply leave the lobster in the freezer or water and salt ice slurry for a long time, long after cessation of movement and respiration. The heart will continue long after that, but even with the brain and other ganglion disconnected, the heart continues to contract. Good luck with the dissection.

author
gizmologist made it! (author)2015-10-29

Though biology isn't my preferred science, taking things apart to see how they work is one of my favorite activities. Maybe the reason I prefer taking apart non-biological things is that they (usually) work again when I put them back together...

Great work, well written.

author

Thank you, gizmologist. And well-put indeed.

author
LouisaB2 made it! (author)2015-10-29

Very interesting, hopefully because you have done a thorough job no one else will feel the need to do it again. I fail to see why the lobster had to be alive for the dissection. Though the scientific evidence is inconclusive on whether they feel pain (with papers supporting both sides), surely the ethical option is to assume they can. I would rather follow the advice of a humane society (http://kb.rspca.org.au/what-is-the-most-humane-way-to-kill-lobsters-and-other-crustaceans_79.html) on how to kill a crustacean than the advice of an institute with vested interests in the support of the industry relying on the death of these animals.

author

Thank you, Louisa, and no the lobster wasn't alive, by traditional means. Although the heart was still beating, it was already deceased. Worry not! I added your link to the humane society method. Thank you much!

author
li james made it! (author)2015-10-28

nice work.

author
rabidwoo made it! (author)2015-10-28

Seeing what's inside of something is the essence of this site.

The greatest form of 'technics' is the living organism...without the living, none of the wonderful things we see on Instructables would be possible. It seems to me that explaining a way to understand the millions of forms of life on Earth is one of the least appreciated forms of sharing (dissect one lobster so the rest of us don't have to) and one of the most needed.

Thanks for posting and I look forward to more!

author
AD8BC made it! (author)2015-10-28

Enjoyed it. Now I'm hungry.

author
Steamcrunk made it! (author)2015-10-28

Clever Instructable. I liked it.

author
shambuda2000 made it! (author)2015-10-28

Hmm, interesting. I must say though, that I prefer them boiled and dipped in drawn butter as opposed to vivisected and pinned. Nice Instructable!

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