Ampullae of Lorenzini Pores on the Snout of a Tiger Shark
Credit: Albert Kok. CC license 1.0, 2.0, 2.5, 3.0
Most of us have heard that it's a bad idea to thrash in the water if sharks are around. It's a really bad idea to bleed in the water if a shark is nearby. But what if you are just swimming, and not bleeding? How will a shark find you? It seems that the deck is stacked in favor of the shark when it comes to finding prey in the water.
There are many species of sharks, so let's focus on the one pictured at the top of the page: the tiger shark. Not only does this shark have an excellent sense of smell, acute eyesight, and acute hearing, but it's also equipped with sensors that can detect electrical impulses emitted by muscles when its prey moves.
Credit: Albert Kok. Used under CC license, 1.2 or later
If you look at the picture that heads my blog, you will note tiny holes around the snout of the tiger shark. These are Ampullae of Lorenzini. They are filled with a jelly-like substance and serve as electroreceptors. Not only can these receptors receive impulses that are sent to the shark's brain when it is pursuing prey, but the electrical signals also help the shark to navigate.
It is believed that the Ampullae of Lorenzini can 'read' signals from the earth's electromagnetic field. A study published in the periodical Current Biography asserts that "...sharks... can travel 20,000 kilometers (12,427 miles) and end up in the same spot...”because of the signals received by the Ampullae of Lorenzini.
Ampullae of Lorenzini,Three-dimensional View
Credit: Chiswick Chap. Used under CC 4.0 license
What substance is in the Ampullae of Lorenzini that conducts the electrical impulses? The substance is a jelly-like mucus that contains a compound, keratan sulfate. Keratan sulfate has conductive properties that are almost as strong as those found in a synthetic polymer widely used in industry, Nafion.
Keratan sulfate's high rate of conductivity may be really good news for the environment. Nafion, which keratan sulfate could conceivably replace, inflicts long-term environmental harm. It has been shown to produce PFC's (perfluorinated compounds) upon exposure to high temperatures and subsequent decomposition. The high temperatures include those that may be reached during incineration.
A study described in the journal Nature reports on the environmental impact of Nafion: "The results of this study indicate that Nafion is a potential environmental source of PFCs, which have attracted growing interest and concern in recent years."
Fuel Cell: Common Use for Nafion
Credit: NASA Public domain.
Why do We Care About PFCs?
It's hard to find a firm and fast statement by a government agency about the health effects caused by exposure to PFCs. However, in 2009 the US EPA managed to issue this rather elliptical statement:
Long-chain perfluorinated chemicals (PFCs) are found world-wide in the environment,wildlife, and humans. They are bioaccumulative in wildlife and humans, and are persistent in the environment. To date, significant adverse effects have not been found in the general human population; however, significant adverse effects have been identified in laboratory animals and wildlife. Given the long half-life of these chemicals in humans (years), it can reasonably be anticipated that continued exposure could increase body burdens to levels that would result in adverse outcomes.
Research Biologist Drawing Blood From Turtle to Check for PFCs
Credit: National Institute of Standards and Technology. Biologist Jennifer M. Keller. Public Domain
When it comes to the environment, and not health, information about PFCs is less ambiguous. According to a report published on the CNBC website, the US EPA has established that PFCs "... are among the most potent and longest-lasting greenhouse gases on the planet..."
The results of a 2020 study published in the Journal of Applied Polymer Science describes another biproduct of Nafion degradation: perfluoroalkanes, PFAs. This study found, as is true of PFCs, that this chemical is released at temperatures, "above 400°C".
A subset of PFAs, PFAA, particularly PFOA and PFOS, are the most well studied PFAS.. This subset of chemicals, indeed all PFAs, are quickly absorbed and accumulate in the body. Here is a quote from the journal Environmental Science and Technology Letters:
After absorption, they distribute from blood to organs and tissues that receive high blood flow, such as the liver, kidney, lung, heart, skin, testis, brain, bone, and spleen. 46,66−70 Because PFAA can occupy sites on multiple receptors, proteins, and cell interfaces in the body, they can produce physiological effects across a range of tissues.
Biomagnification: the Further Up the Food Chain, the More Concentrated the PFAs
Credit: Yanishevsky. Used under CC 4.0 license
The high rate of electrical conductivity in Ampullae of Lorenzini has been explored for potential application in the field of bioelectronics. Fuel cells specifically have been mentioned. Instead of using Nafion, it has been proposed that one could use material found in the Ampullae jelly. Here is an excerpt from the journal Neural Regeneration Research: "The ampullae electrosensory gel has conductive properties rivalling the Nafion electrocytes of fuel cells and is the most sensitive proton gradient detection system known in nature..."
Imagine replacing Nafion with natural, biodegradable material. This is potentially the promise contained in research on Ampullae of Lorenzini conductivity.
Simply put, the promise of bioelectronics is the "convergence of biology and electronics". This convergence would have utility not only in industry, but also in medicine.
Mammalian Corneas Are Rich in Keratan Sulfate
Credit:@yaziris, LMAC Image Library Keratan Sulfate has a role in mammalian tissue as a neurotransmitter.
Electronic devices have already been integrated into routine medical practice. The frontier for development of this technology is wide open. The University of Chicago's Center for Entrepreneurship and Innovation, for example, describes development of Stretchable, Self-Powered Bioelectronics (that) Mimic Skin in Form and Function. The university's website explains that researchers are "Drawing on innovation in the fields of semiconductor physics, solid mechanics, and energy sciences..."
Manta Ray Use Ampullae of Lorenzini
Credit: G.P. Schmahl, NOAA. Public domain. That manta ray (unlike the stingray) does not hunt prey with its electrical signalling ability. It instead avoids being eaten by sharks by detecting these predators in the water.
When exploring the highly conductive properties of the Ampullae, researchers at the University of Santa Cruz consider how this relates to the development of "biomaterials". The materials might be used to treat a variety of conditions. For example, there is potential for development of a "bioprotonic device that could...be used therapeutically in epilepsy or other disorders".
My interest in Ampullae of Lorenzini began when my granddaughter mentioned them to me. I'd never heard of this before and started reading. A door opened. Not only do sharks use this electronic signalling, but so do many marine animals. While many marine animals have electric signalling, almost all "land vertebrates are not known" to have it
Platypus, Rare Instance of Terrestrial Animal With Electrical Signalling
Credit: Peter Scheunis. Used under CC 1.0 license. The platypus as modified trigeminal nerve fibers that can pick up electric signals from prey.
After my granddaughter introduced me to this subject, I became fascinated by the intersection of technology, biology, and the environment. As I learned more, I thought it might be interesting to share the information with the Hive community. My one ethical concern (the little I know) is that bioelectronics might imply harvesting biological material from live animals. That development would be unacceptable.
I hope my readers find this exploration as intriguing as I do. Thank you for reading. Be well. Be peaceful, and as always,
@muelli, from the LMAC Image Gallery
@agmoore, self made:
@yaziris, from the LMAC Image Gallery