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Badass Biology: The Pistol Shrimp

April 26, 2012 0Comments

“Wtf, shrimp!!? I make it all the way to this website from who knows what part of the internet, and I see ‘Badass Biology’. Man, Kevin, you flip my brain out with possibilities of flying sharks, rabbits of doom, or a half-honeybee half-unicorn rainbow pollinators. And what do you deliver? A stupid shrimp??! I hate you, and I quit this website. (╯°□°）╯︵ ┻━┻)” To which I reply, “Charles Barkley, I think you’re over-reacting. Please repair my table at once”.

It was hard to find a chart that even went up to 150dB, let alone the 220 these guys produce.

Yes, it’s a shrimp. A measly two-inch-long shrimp. But you don’t understand. This one single stupid shrimp is just about the coolest thing I’ve ever heard. Trust me, and when you hear one too, you’ll probably go deaf, because this one little shrimp IS ONE OF THE LOUDEST ORGANISMS ON THE PLANET. I’m talking 220+ decibels, much louder than a gunshot and louder than standing next to a jet engine at take-off. O_o.

First, I want to talk about some other wicked cool stuff this little guy does apart from being a tiny walking firework of sonic pain. These shrimp garner lots of attention from ecologists because of their symbiotic, or mutually-beneficial, relationship with gobies, a type of small marine fish. The coral reef populations of this shrimp build burrows and recruit the help of a goby to stand guard out front while being no more than an antennae’s distance from the shrimp, using the goby’s well-developed vision to watch for danger. Once danger comes, the goby flicks its tail to signal a threat, and both the goby and the shrimp retreat into the same burrow. Then they start slapping five. It’s flippin sweet.

The mutualisms don't just end at gargoyle-ing.

From an ecologist’s point of view, this is totally mutualistic, and some scientific literature lists this interaction as “totally f-ing amazing” [citation needed] (Good luck with finding THAT reference -ed.). Yeah, both the goby and the shrimp live to see another day should a shark, barracuda, squid, rogue buoy, really fast snail, very-misplaced land predator, sinking boat part, cloud of wasps, or sentient shrimp-hating spear come around to threaten them. The goby gets a burrow, and the pistol shrimp gets a gargoyle. Selection at work.

I like to think of the goby as the pistol shrimp’s pet, kinda like me buying a falcon and parading it around the neighborhood on a leash. And once danger comes, the falcon goes “Hey yo, Kevo, you might need to reconsider this route”, we split, we don’t find danger, and I buy the falcon ribs for a job well done (and because I really want ribs right now). So in a sense, pistol shrimp are danger shepherds equipped with sun-blasting cannons of glory that we’ll get to in a moment.

I need to take a break to collect myself. Holy balls, these shrimp own everything own-able. Next time I see one, I’m buying it ribs. The whole rack.

Let’s get to that “pistol” thing, why don’t we? Pistol shrimp have one very distinct set of front appendages, like two arms extending outwards from its body. Only, one of these arms is disproportionately larger than the other, and it’s quite a contrast. Like no foolin’ man, this one arm alone can be as long as half the entire length of the shrimp’s body. Imagine walking around with one of your arms the size of the Hulk’s and you get the idea. This may look pretty stupid, but this powerful musculature operates one of the most badass weapons nature can offer.

Yeah, kinda like this

When in serious danger or when hunting, the pistol shrimp cocks its massive claw backwards into a 90o position. Once the claw snaps shut, it produces a jet of water propelled forward at 60mph. Yeah, woo, a fast water jet. Big deal. But here’s the amazing part. Are you ready to have your mind blown? If you have ever listened to me before, now is a pretty good time, too: This jet of water creates a bubble that cavitates, or implodes, generating a pressure wave that creates a sound loud enough to break glass in an instant. Not only that, but once the bubble cavitates, the heat generated by the force of the implosion causes the temperatures inside the bubble to reach about 18,000 degrees Fahrenheit. Yes. Eighteen. Thousand. Oh, and to top it off, the whole process takes three tenths of a second. 

THIS TINY SHRIMP MAKES A BUBBLE SO AWESOME THAT IT’S LOUDER THAN A JET AND MORE THAN TWICE AS HOT AS THE SURFACE OF THE SUN.

 

You can imagine the horribly bubbly doom the pistol shrimp’s enemies must face. Stunned (or killed) by the force of that kind of pressure change, the pistol shrimp’s prey has basically just become lunch in an instant. The shrimp pulls its quarry into its burrow, and goes to town, just how I could go to town on some ribs right about now. I dug up a video about this whole process in case what I said wasn’t convincing enough:

http://www.youtube.com/watch?v=eKPrGxB1Kzc

If you want me to write about any other badass biological bosses, leave a comment. I may talk about them, or I may just tell you that your suggestions are awful. Probably not the latter though. I like people.

Well, I like most people except you, Charles Barkley. I really miss that table. Now I’ve got nothing to rest my wine on when Glee’s on.

Photo credits:

http://www.airpowered.co.uk/images/dbachart.jpg

http://loyalkng.com/wp-content/uploads/2009/11/arm_wrestling_champion_03.jpg

 

 

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Kevin Wolfe
About Author

Kevin Wolfe is pursuing his Ph.D. in Marine Biology from Texas A&M University-Corpus Christi. Kevin has had three battleships named after him, including a Belgian vessel. His valor and use of his falcon in battle have earned him the nickname "Hawkguy", which everyone thinks is "Hawkeye" because nobody has ever taken time to fully pronounce the g. As a scientist, he is the cornerstone of all things biology. He once earned a posthumous Nobel Prize, reconstituted his form as a different person, won another Nobel Prize, died again, and reformed a second time. He is currently working on his third Nobel Prize and is considering authoring a book on authoring books. Kevin enjoys breakfast tacos.

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  Timothy Durham was convicted of rape when a test showed his DNA genotype matched the DNA recovered from the crime scene. Eye witnesses testified that Durham was in a different state at the time of the incident, but he wasn’t exonerated from his 3000 year sentence until follow up DNA analysis showed that the preliminary forensic analysis used in the trial was misinterpreted (Thomas et al.). DNA testing serves an invaluable part in our criminal justice system, but it comes with complications and bias that can lead to wrongful convictions and misinformed juries.  

Background:

Forensic genetics aims to identify the origin of a biological sample. It can be traced back to Karl Landsteiner who discovered human ABO blood groups. With blood groups, suspects could be eliminated based on their blood type. For example, if a suspect had type A blood and there was type B blood left at the scene by the perpetrator, the investigators could rule out the suspect. Unfortunately, the reverse didn’t work. If the suspect and perpetrator both had the same blood type, it can’t be concluded that the suspect was guilty. Blood identifiers evolved into 8 distinct categories which improved the ability to eliminate suspects, but could only conclude that (if the system matched) it might be the perpetrator or this person might be related to the perpetrator (Jobling and Gill). The field evolved in the 1980s with the discovery of Minisatellites, lines of repetitive DNA that don’t encode proteins. Minisatellite patterns in DNA create what we know today as the DNA fingerprint, and it has a much higher accuracy rate than previous methods (Augustyn et al.). Around the same time, a breakthrough for victims of sexual assault was discovered. In the case of assault, bodily fluids of both the victim and the assaulter can get mixed. A process called differential lysis was created which could selectively increase the concentration of sperm in a fluid sample thereby allowing for accurate DNA testing (Jobling and Gill). Forensics evolved to use single-locus probe testing after several years because of its ease of interpretation. It looked at specific minisatellites that had high variability between subjects. This was the first DNA-based method to be used in a criminal investigation. Two murder homicides from several years apart were connected using DNA evidence. The evidence was then used to exonerate an innocent man, and the guilty party was found when he tried to evade mandatory DNA testing for all men in the small town. His guilt was then reinforced when the DNA profiles matched, and he gave a confession (Jobling and Gill). Finding DNA at a crime scene doesn’t guarantee that you’ll find a murderer. There are issues with non-pure samples and limited samples that make DNA work difficult, and accreditation of facilities and new techniques and take time (Jobling and Gill).  

Subjectivity of DNA Interpretation:

In a 2009 publication, the National Academy of Science discusses the possibility for subjective influence in lab based forensics. The interpretation bias happens in complex cases where, for example, there could be a mixture of DNA. A study published in 2011 looked specifically at this issue. A gang rape happened in Georgia, and the mixture in DNA from the case was used to prosecute one suspect after another suspect took a plea bargain to testify against him. With DNA mixtures, there are three possible conclusions: suspect excluded, suspect cannot be excluded, and inconclusive. If the suspect is excluded, it means that there’s little to no possibility that his DNA is part of the sample. If the suspect cannot be excluded, it means that there’s a possibility that his DNA is part of the sample. In the trial, the DNA examiners who knew the context of the case concluded that the suspect being prosecuted could not be excluded. The 2011 study gave the DNA evidence from this case and the DNA profiles of the suspects to 17 forensic examiners. These examiners had no context of the case, and they all worked independently. Of the 17, only 1 came to the same conclusion (suspect cannot be excluded) as the examiners who knew the context of the case. Twelve of the 17 concluded that the suspect who was prosecuted and convicted had no relation to the DNA found in the sample. Not only does this show that subjectivity occurs due to the context of the case, but the 17 examiners came up with different findings based on their past experiences meaning that not all DNA analysis is objective. Some organizations like the Scientific Working Group on DNA Analysis Methods say that quantitative statistical evidence should be presented with every categorical conclusion, but the US doesn’t require this (Dror and Hampikian).

False Positives:

There are two categories that cause wrongful identification in a DNA report: coincidental matches and false positives. Coincidental matches are DNA matches between two unrelated people. The probability of these matches is about 1 to 500,000 for white individuals and about 1 to 350,000 for black individuals. This small probability of coincidental matches makes people feel confident in DNA evidence. False positives, on the other hand, are matches between DNA and test DNA that result from issues in the forensics lab. There have been multiple cases of forensics labs accidentally switching victim and suspected rapist DNA which lead to convictions that were later overturned when the lab realized the error. There are also cases of misreading or misunderstanding a sample. In a case from 1993, a man was convicted of rape because someone interpreted a mixed sample of victim and perpetrator DNA as an individual sample. The conviction was again overturned. To prevent false convictions, retesting DNA is allowed, but it’s not an efficient solution. Many people are pushing for statistical information on the probability of false positives, so that the jurors can make accurate judgements based on DNA evidence (Thomas et al.).  

Conclusion:

DNA analysis is a useful tool for the criminal justice system, but subjectivity can be an issue in forensic testing. To combat wrongful convictions, there are organizations like The Innocence Project who use DNA testing to free the innocent, but reformed forensic testing standards should be put in place to prevent subjectivity and to ensure juries are correctly informed during trials. https://www.innocenceproject.org/    

Citation:

Augustyn , Adam, et al. “DNA Finerprinting.” Encyclopedia Britannica , 26 Apr. 2018, www.britannica.com/science/DNA-fingerprinting#ref153186. Dror, Itiel E., and Greg Hampikian. “Subjectivity and Bias in Forensic DNA Mixture Interpretation.” Science & Justice, vol. 51, no. 4, 2011, pp. 204–208., doi:10.1016/j.scijus.2011.08.004. Jobling, Mark A., and Peter Gill. “Encoded Evidence: DNA in Forensic Analysis.” Nature Reviews: Genetics, vol. 5, no. 10, Oct. 2004, pp. 739–751., doi:10.1038/nrg1455. Thompson, William C, et al. “How the Probability of a False Positive Affects the Value of DNA Evidence.” Journal of Forensic Sciences, vol. 48, no. 1, Jan. 2003, pp. 1–8., doi:10.1520/jfs2001171.