Pennywise, the dancing clown
The newest addition to our mantis shrimp family is a gorgeous green-black Gonodactylus smithii named Pennywise. The Gonodactylus genus has been my fourteen-year-old brother’s favorite genus ever since I told him that it essentially means scrotum fingers, as the two raptorial appendages held at the ready take on a somewhat humorous shape. For a review of mantis shrimp anatomy, see my last post here. The species name, smithii, is related to the word smithy, or blacksmith, presumably because blacksmiths and this mantis shrimp like to hammer things. Unlike the relatively tame Odontodactylus scyllarus (peacock) mantis, this species has significantly bigger hammers, and as such packs a bigger punch. I made the mistake of proffering my nail only once. When particularly aggravated, he will detach his dactyls from his propus and extend it toward me, revealing a cruel hook at the end that’s usually hidden, as though he’s flipping me the bird. A little high pitched voice in my head dubs him screaming “curse youuuu!!!” whenever he does this.
Pennywise on our makeshift operating table with his backpack affixed to his carapace. Wires have yet to be cut and inserted into his merus.
In my last post, I made up a thought experiment that would be useful once I started gathering data: What does it mean to the mantis shrimp that I put my finger near his burrow and then pull it back when he strikes every minute or so for a period of time?
You might predict that after a few intervals of striking, the mantis shrimp would no longer strike as readily. Perhaps it would strike every other time, and after a few more intervals, every five times, and then not at all. This kind of learning is called habituation, and can be a big confound in experiments involving behavior, and occurs because the mantis slowly realizes that I am not a real threat (after all, I’m not punching back and I retract my finger after one punch). But, the mantis shrimp does not have a perfect memory, so it there might be a longer interval than one minute where the rate of habituation would be so slow as to not happen at all. In other words, if I waited long enough between events of sticking my finger in the water, the mantis shrimp may not remember as clearly that I presented no real threat, and would probably punch with punctual predictably.
Featherclown is pictured on the right, photogenically showing off said Patek restraint, though he didn’t feel like punching that day.
Houston, we have more than one.
I’ve been mulling over this thought experiment a lot because this past Friday, I got my first round of data! Pennywise was kind enough to lend his EMGs for several rounds of Q-tip-coated-in-shrimp-paste bashing. As soon as I put the Q-tip in front of him, he hit it with a vengeance. As with the second time; however, the third time, I had to prod him a little. The fourth time, he seemed disinterested. Evidently, Pennywise habituates very fast. I left him alone for a bit, hoping the habituation would wear off, and returned a few minutes later. After a mere 20 minutes or so, he was done for the day. Next time, I’ll try to space out my Q-tip presentations a bit more, otherwise Pennywise might become totally habituated to my stimuli.
I placed the probes in Pennywise’s extensor, the muscle that is responsible for building up the strike power, and here’s what we got! On the top in red is the audio trace. I’ve highlighted the sound of the pop from Pennywise striking a Q-tip. I don’t know if there would be observable cavitation here since the Q-tip is soft and held lightly, so this pop is probably just the sound of the dactyl heel hitting the target. The small green jagged spikes are the extensor’s activity, representing muscles twitches that are adding energy to the “spring”, or saddle. As I noted in my first post, this activity should represents the coactivation phase, where the flexor and the extensor both tense to build up energy in the saddle. Let’s compare the original paper with these data.
Obviously, my spikes aren’t as large as the ones in the journal article, but you can kind of tell that my trace is probably in the coactivation phase. I’m looking forward to collecting more data and starting to find patterns. Also, there’s another member of our mantis shrimp family coming in the next few days! Keep an eye out for my next and final post where I talk about results and the surprising namesake of the Squilla empusa, currently travelling in luxury by way of the US Postal Service.
One of the most attractive things about a BYB Summer Fellowship is the chance to spend a summer in colorful Ann Arbor. We changed the program name from an internship to a fellowship because of the lasting connections made throughout the summer, and these connections are made possible by the things we all do together! Before we get to some project updates, here’s a little bit about our summer together so far.
Take Me Out To The Ball Game
Last summer, we sponsored a student whose visa required participation in a “cultural appreciation” event, so we piled into a bus and headed over to Comerica Park for some of America’s favorite sport, baseball. It was such a hit, we went again this year! Luckily, Backyard Brains signature color (orange!) matches pretty well with the Tigers brand 😉
Fourth of July Parade
Another celebrated BYB Summer Fellowship pastime is the Jaycee’s Fourth of July Parade! Each year, the fellows design and build a costume representing their summer research and wear it as BYB walks in the annual parade! Check out some of the looks from this year:
Meet the Fellows, See the Projects
Catch up with our Fellows! Since our Fellowship started, each fellow has been hard at work on their summer research. Check out these posts introducing each Fellowship research track:
First Progress Reports:
If you’ve been dying for an update on what we’ve been researching, fret no more! Feast your eyes on our first batch of updates!
Second Progress Reports:
Science marches ever onward! The Fellows have kept plugging away on their research in between all the fun and games, and here are their newest updates!
Conclusions:
The summer is winding down, and with it our Fellowship. While scientific exploration is never really finished, here are some wrap-ups from our Fellows on the projects they have devoted their inquiry to over the past weeks.
I want you to do me a favor. I want you to hit me as hard as you can.
What’s that? You want more background?
Folks, things have started to pick up. Perhaps the most important development since June 11th has been the christening of our two mantis shrimp, which will give me an excuse to talk about mantis shrimp anatomy. We have two mantis shrimp living in our humble makerspace, All Hands Active: Toothfinger and Featherclown.
Toothfinger’s name comes from his scientific name, Odontodactylus scyllarus. To break that down, “Odonto” means relating to a tooth or teeth (think dentist), and “dactylus” is related to a greek word for finger. Featherclown’s name comes from two common names for Odontodactylus scyllarus, the peacock mantis shrimp (peacocks having those big colorful feathers), and the harlequin mantis shrimp (harlequin meaning clown, not the Joker’s love interest).
Anyway, let’s get into the anatomy that gave Toothfinger his name: the second raptorial maxillipeds, or as scientists in the field call them, his raps. The raps are 4-part “fingers,” composed of a the merus (the “femur”), the carpus (think the carpal bones of the hand), the propus (the “tibia”), and finally the dactyl. I briefly mentioned the concept of power amplification in my first post. It’s the way mantis shrimp are able to store up and quickly release an immense amount of energy that a single muscle twitch cannot accomplish by itself. This energy is stored in a sort of “spring” embedded in its rap called the saddle.
The seminal work on this spring action, as well as the EMG work I cited in my last post, was done by Professor Sheila Patek. In addition to being a true science badass (podcast) and an alumnus of my school, UMass Amherst, she discovered the mechanism of power amplification in mantis shrimp. The saddle shape on the merus is known as a hyperbolic paraboloid, a shape that shows up in architecture and origami. Here’s a gif of my Starbucks paper bag—turned saddle, resisting deformation. This should give you a sense of how the saddle stores and releases energy. By using multiple twitches, the extensor muscle in the merus compresses the saddle further and further, twitch by twitch, until the energy is released by the flexor.
Facing the 3-inch long beasts
Having done recordings in several insects, I felt that I had enough data for a preliminary cross-species analysis of EMGs between insects and the mantis shrimp. Meaning that I had to face the prospect of touching Toothfinger and Featherclown, those murderous bastards. However, it turned out that the challenge wasn’t in keeping my fingers intact, but in getting the stomatopods to punch at all.
The juicy bits of mantis shrimp behavior happens inside of and around their burrow: they grab whatever comes too close to the opening, recede into their lair, and get to work opening up the shell with intermittent audible clicks. Some of the first work on mantis shrimp from the ‘60s detailed their territoriality. Most social interactions involve burrow eviction/defense, where one stomatopod has to demonstrate dominance over another individual who wants its to steal its digs, no pun intended.
So their striking is closely tied to their burrow. My first attempt to get them to punch involved making a behavioral chamber that simulated a burrow. No dice. Featherclown just sat there. Then, I tried copying Sheila Patek’s restraint paradigm from her EMG paper, and again we encountered a distinct lack of dice. Odds are I’d have to invest a lot of time in habituating the animals to a restraint setup, plus it’s not burrow-like at all.
Left: my attempt at a simulated burrow
Right:Sheila Patek’s restraint design
I was feeling a bit lost, and then I noticed another paper from the Patek lab had come out on this year with a methodological stroke of genius: just use the actual burrow! In the lab, a mantis shrimp burrow is usually an ~6-inch long PVC pipe. Why not open a window lengthwise along the pipe, and place the window against the glass?
All that was left was to see if they’d strike from their new burrow, so I stuck my hand into the tank.
Holy reliability, Batman! If spaced out by a minute or two, I can pretty much elicit a strike every time. Here’s a fun thought experiment: what does it mean to the mantis shrimp that I put my finger near his burrow and the pull it back when he strikes every minute or so for a period of time?
To hear more about how Professor Sheila Patek’s scientific badassery, check out this podcast, and to hear about how she ended up making this discovery, check out her TED talk.
Short bibliography
Crane, R. L., Cox, S. M., Kisare, S. A., & Patek, S. N. (2018). Smashing mantis shrimp strategically impact shells. The Journal of Experimental Biology, 221(Pt 11), jeb176099. https://doi.org/10.1242/jeb.176099
Dingle, H., & Caldwell, R. L. (1969). The Aggressive and Territorial Behaviour of the Mantis Shrimp Gonodactylus Bredini Manning (Crustacea: Stomatopoda). Behaviour, 33(1–2), 115–136. https://doi.org/10.1163/156853969X00341
Patek, S. N., Korff, W. L., & Caldwell, R. L. (2004). Biomechanics: Deadly strike mechanism of a mantis shrimp. Nature, 428(6985), 819–820. https://doi.org/10.1038/428819a
Kagaya, K., & Patek, S. N. (2016). Feed-forward motor control of ultrafast, ballistic movements. Journal of Experimental Biology, 219(3), 319–333. https://doi.org/10.1242/jeb.130518
