Some animals have been farming for much longer than humans.
Thousands of years ago, farming revolutionized human societies. It allowed us to settle in one place and to have surplus food, freeing some people to pursue other specialized labor. Populations grew, cities flourished. Today, it is impossible to think about life without agriculture. But did you know that some animals have been farming for much longer than us?
Insects are probably the most well known farming animals, but accomplished farmers have been documented among fish, crustaceans, and mollusks as well. Even microorganisms have been reported to farm. In 2011 a group of researchers reported on the amoeba Dictyostelium discoidelium, which farms bacteria.
Some animals practice very advanced forms of agriculture, which include preparing the growth medium, propagating their crop, tending their gardens, fertilizing and harvesting the crop, and transmitting it from parents to offspring. The most advanced forms of animal farming belong without a doubt to the insects, but many other animals practice simpler farming techniques too.
Meet some of these amazing animals below, and stay tuned to Part 2 of this series for a look into the more advanced farming species.
In 2005, researchers discovered a new species of crab, Kiwa hirsuta, at a hydrothermal vent in the South Pacific Ocean. It was a bizarre creature, covered in hair-like structures called setae, which earned it the common name of Yeti crab. However, only one specimen was collected, and many questions remained about the crabs’ diet and feeding strategy.
Then, in 2006 a second Yeti crab species was discovered off the coast of Costa Rica, on a methane seep. These crabs, Kiwa puravida, displayed an odd habit of rhythmically waving their claws over areas of methane seepage (see video below).
Examination of different specimens revealed that the hairy structures on the crabs’ claws were covered by chemosynthetic epibiotic bacteria. By studying the composition of the crabs’ tissues, researchers were able to determine that these bacteria constitute the Yeti crabs’ main food source. The crabs fertilized their bacterial crops by swaying their claws over the methane seepage sites, allowing nutrients to wash over the bacteria. They then use a specialized mouth appendage to transfer the bacteria from the setae to their mouths.
Video S1: Kiwa puravida at Mound 12, Costa Rica demonstrating the rhythmic waiving of its chelipeds (Thurber et al., 2011).
In 2015, a third species of Yeti crab was discovered living on hydrothermal vents in the Antarctic Ocean, Kiwa tyleri. Dense setae covering its ventral side give it the appearance of a hairy chest, for which it has been nicknamed the “Hoff crab“, after the actor David Hasselhoff.
Damselfishes are a group of small to medium fish living mostly in saltwater ecosystems, and many of which inhabit the world’s tropical coral reef systems. They have a reputation for being feisty and territorial. Damselfishes feed on small crustaceans and other small organisms, sponges, and algae. Some algae- eating damselfish species are actually accomplished gardeners, tending carefully to their algae garden, from which they feed.
The damselfish Sterogastes nigricans. Photograph by Hata et al., BMC Evolutionary Biology.
The damselfish Stegastes nigricans,a little fish with an unassuming appearance, is one such dedicated farmer. It inhabits tropical coral reefs between 30°S and 30°N of the equator, and assiduously keep patches of the filamentous red algae Polysiphonia sp. It keeps watch over his algae patch aggressively, weeding out other algae species, and defending the patch against other herbivores. Researchers observed that when damselfishes were removed, other species of algae readily invaded the Polysiphonia patches.
Although this behavior is beneficial for both damselfish and algae, there might be some negative effects for the health of the coral reef. In its effort to create space for its algae garden, the aggressive weeding by the damselfish prevents coral polyps from attaching. Also, the algae in their garden can harbor bacteria associated with coral disease. In a 2014 research paper, Casey et al. reported greater bacterial concentration and incidence of black band disease within S. nigricans territories than outside.
Littoraria irrorata, also known as the Marsh periwinkle, is a species of salt-water snail that lives in salt marshes on the Atlantic and Gulf coasts of North America. This surprising little farmer grazes on stalks of cordgrass, but not to eat. Rasping with its radula, it creates longitudinal grooves on the stalks. Opening up the plant’s tissues facilitates invasion by ascomycete fungi, which are abundant in the salt marsh environment, and are the periwinkle’s preferred food.
These snails have even been observed fertilizing their fungus crops with their feces, which are rich in nutrients and fungus hyphae.
Source:
Silliman, B.R. and Newell, Y. 2003. Fungal farming in a snail. Proceedings of the National Academy of Sciences, 100(26): 15643-15648.
These are just a few examples of animals that have developed farming relationships with their food, a type of symbiosis referred to as cultivation mutualism. In the next post, we’ll learn about some of the more advanced animal farming societies.
Check out some of last week’s most interesting news stories:
1. Generating Power from Polluted Air
This small device can generate hydrogen fuel while purifying polluted air. Photograph by UAntwerpen and KU Leuven.
Air pollution is a major environmental issue, and a cause of health problems affecting millions of people globally. Fuel combustion is one of the main causes of air pollution, and scientists are earnestly trying to find solutions for air remediation, as well as alternative energy sources that are more environmentally friendly. Researchers from Belgium recently reported on a way to do both using a single device, which can turn air pollution into fuel. And it gets even better, it needs only light to operate.
It is a very simple device, consisting of two chambers separated by a membrane. The membrane is made of special nanomaterials that act as catalysts. Contaminants are degraded on one side, and hydrogen gas is produced on the other. The gas is stored and can be used for fuel. The device is currently very small, but the researchers are working on scaling up the technology.
Verbruggen, S.W., et al. ChemSusChem. DOI: 10.1002/cssc.201700485.
2. Spray-Painting Touchpads
Researchers at Carnegie Mellon have shown that touchpads need not be restricted to the flat surfaces of phones and tablets anymore.
No longer will touchpads be restricted to flat phone or computer screens. Researchers at Carnegie Mellon have figured out a way to turn almost any kind of surface into a touchpad. The technology, which they presented at the Conference on Human Factors in Computing Systems last week, is based on the use of an electrically conductive coating that can be applied as easily as spray painting. When a finger touches the surface, some of the electric current is steered to ground through the hand, temporarily lowering the voltage. The researchers showed that it is possible to localize, with up to 1 cm of precision, where and when this occurs by using electrodes connected around the edges of the coating.
Apart from spray painting, other methods like 3D printing can be used to apply the coating, or even make the entire object using the conductive material. The researchers have already used the technology to create touchpads on several different surfaces, including a steering wheel, a guitar, and even jello. The possibilities are endless. Check out the video below to see how it works.
Video by Future Interfaces Group, Carnegie Mellon University.
Recently, researchers at the University of Minnesota developed a 3D printed flexible electronic sensory device that could be used to give robots the ability to sense their environment. It consists of several layers, including a bottom silicone surface, and top and bottom electrode layers separated by a pressure sensor shaped like a coil.
An interesting application of these sensory devices would be to put them on surgical robots, which would allow the surgeon to feel during the operation. Furthermore, because the material can be printed at low temperatures, it could be used to print on skin. This opens up many practical uses for these sensors, such as printing wearable patches for health monitoring.
Visit the University of Minnesota webpage for more details, as well as a video of the printer in action.
Researchers at Lancaster University are making it easier to turn used coffee grounds into fuel.
Did you know that used coffee grounds can be used to produce biodiesel? Biofuels produced from feedstocks are generally not the ideal replacement for fossil fuels, because of all the resources required to grow them. Used coffee grounds, however, offer a convenient, low-cost alternative. Unfortunately, their commercial competitiveness is negatively affected by high processing times and costs. Consequently, very few companies are currently taking advantage of this potential biofuel source, and most of the spent coffee grounds that are produced daily end up in landfills.
In a study published earlier this month, scientists from Lancaster University figured out a way to make the process much more efficient than what was previously used. While the technique typically involves two steps, one for extracting the oils and another for turning them into biodiesel, they showed that it is possible to do both steps at once. This modified process dramatically cuts down on processing times and costs, and will hopefully lead to a greater exploitation of this alternative fuel source.
Cricket farm in Thailand. Photograph by Afton Halloran.
It is well known that meat production places a high burden on the environment. Insects have often been called the food of the future because of their high nutritional value, and potentially lower environmental impact. Recently, a study on the sustainability of crickets as a food source showed that they can in fact be produced in a more environmentally friendly way than other livestock. The study compared the environmental impact of cricket and broiler chicken production in Thailand, by focusing on certain ecological markers, such as eutrophication and resource consumption.
They found that in most of the markers studied, cricket farming had a smaller ecological footprint. In both cricket and chicken farms, feed production was one of the areas with the highest impacts. Although it is not their natural diet, farmed crickets are fed chicken feed because it makes them grow faster. However, crickets are more efficient in turning the feed into animal protein, thus resulting in a lower impact than chickens. Researchers are now working on finding better feed sources for commercially farmed crickets in order to reduce the ecological footprint of raising them even more.
To learn more about the story, visit the University of Copenhagen website.
Check out this week’s summary of some of the most interesting science news:
1. Killing Bacteria with…Paper?
Flexible, paper-based plasma generators can inactivate microbes within seconds (Photograph by Jingjin Xie).
Scientists from Rutger’s University have developed a new flexible, portable and disposable device for killing bacteria using metallized paper. It consists of stacked layers of paper covered with aluminum in a honeycomb pattern. When high voltage is applied, plasma is generated. Plasma is a mixture of ions, reactive molecules and UV radiation, which is regularly used to kill bacteria. In these devices, the stacked, porous paper allows gas to permeate it, which in turn is fuel for the plasma and allows for cooling. The researchers showed they were able to inactivate 99.9% of E. coli cells after just 30 seconds of treatment. Further research is needed to assess how effective these devices are at eliminating spores, but preliminary results look promising.
In the future, this specialized paper could be used to clean laboratory equipment, as sanitizing bandages for wounds or as protective layers in clothing. Part of the researchers’ motivation was to develop clothes that could self-sterilize after being exposed to pathogens, like in the case of health workers during the ebola epidemic of 2014.
Researchers from Stanford University developed a new flexible, biodegradable semiconductor, shown here on a human hair (Photograph from Bao Lab).
With the short lifespan and accessibility of electronics, electronic waste, or e-waste, is quickly becoming an ecological problem. Electronic circuits are made from non-biodegradable materials, often containing toxic substances like heavy metals. Looking for potential solutions to this mounting problem, a group of researchers from Stanford University developed a flexible, biodegradable semiconductor polymer that decomposes when exposed to mild acids. In addition, they developed a biodegradable electronic circuit, and a degradable substrate to hold everything together. The film-thin substrate is made from cellulose and can stick to rough and smooth surfaces. The best part is, when the circuit is no longer needed, everything can easily be degraded.
This new electronic device has the potential to be used in a variety of applications, including wearable electronics, like skin sensors to monitor glucose or blood pressure, and even implantable devices.
3. Water-Repellent Material Inspired by Snake Skin
In yet another example of scientists being inspired by nature, a research group from the University of Freiburg, in Germany, has developed a new water-repellent material that, when damaged, is capable of shedding its outer layer, much like the skin of a snake. The material comprises three layers, an upper water-repellent material, a middle layer made from a water-soluble polymer, and a super-hydrophobic silicon layer at the bottom. When the top layer is scratched and the material is submerged in water, the middle layer is dissolved and the top layer peels back, exposing the hydrophobic layer underneath.
Current water-repellent materials are sensitive to mechanical damage, leading to water permeation. In contrast, this new development could lead to the development of self-renewing water-repellent materials, like cloth for raincoats, that could restore their own hydrophobicity after damage. Check out the video below to see this snakeskin-like material in action.
4. “Princess Pheromone” Is Expressed by Future Queen Ants
Adult working ants carefully inspect larvae to detect which show signs of becoming queens (Photograph by Clint Penick)
Every summer, around the time of the first rains, new queens of Indian jumping ants, Harpegnathos saltator, develop. Worker ants carefully groom them until they are ready to mate with the flying males, and later they leave to found their own colonies. But how do the workers distinguish between would-be queens and normal worker larvae? In a new study, led by Clint Penick from North Carolina State University, researchers identified a pheromone, which they call “princess pheromone,” produced by larvae that are preparing to become queens. This chemical communication allows adult ants to know which larvae are turning into queens, and thus work to ensure their proper development.
Interestingly, when the princess pheromone is expressed at inappropriate times, adult ants respond in a radically different fashion. When the timing is off for mating, or when there are already too many queens in development, adults respond by biting the larva expressing the pheromone. Harassed into submission, the larva subsequently develops into worker. This behavior allows for conservation of resources, as well as preservation of colony structure by preventing the development of more queens than the colony can support.
High-resolution satellite imagery offers a less disruptive and more cost-efficient alternative to keep track of albatross colonies in remote islands.
The albatrosses are a group of large, marine birds comprising several species, a number of which are critically endangered. It is difficult to keep track of their population numbers, because they nest in remote islands that are often unpopulated and hard to reach. But now, in a study published in the journal Ibis, scientists show that the highest resolution satellite images can capture individual albatrosses, making it possible to count them without actually having to be there.
In this study, they used 30-cm resolution images from the WorldView-3 satellite to count a Wandering Albatross colony in South Georgia, a well-studied group, and found the numbers comparable to ground-counts of nests. They then applied the technique to count a remote colony of endangered Northern Royal Albatross in the Chatham Islands, which had not been counted recently, and made a concerning discovery. On one of the islands, the satellite count was significantly lower than the previous ground-count, which illustrates the importance of frequent population counts for conservation efforts. The use of this new satellite imagery offers a great alternative for better and less disruptive monitoring of bird populations, which is especially important for endangered species.
The king was down! Dropping everything, he had followed his master into the rain, through the throngs of soldiers, into the confusion of battle. The air stank of death. The king was bleeding profusely, there was no time to lose. Working quickly, they applied the venom over the wound and …the bleeding had stopped. The King would live. Sitting under the stars that night he wondered, as he had so many times before…how could something so deadly, give life? His own brother had died as a child from the snake’s bite and yet, King Mithridates lived because of it.
“Meadow viper (Vipera ursinii)” Public Domain. Agari healers travelling with his host saved king Mithridates’ life by applying venom from the meadow viper to his wound.
It was the year 67 B.C. and king Mithridates VI of Pontus was waging war against the Roman Republic. He became injured in battle and was bleeding heavily. His Agari healers, members of a Scythian tribe that traveled with his host as physicians, saved his life by applying the venom of the meadow viper (Vipera ursinii) to his wound to stop the bleeding (1).
Fast forward to the 21st Century, in a different part of the world…It was a game of hide and seek. Scouting the terrain with anxious eyes, she finally found the perfect hiding spot. They will never find me here, she thought, grinning . As she knelt behind the termite mound, careful not to make a sound, she felt a sting on her shoulder. Pain gave way to horror as she turned and discovered the snake. And not just any snake, a black mamba. It too had been hiding behind the termite mound, basking. She alerted the kids and they ran to their mother, but it was too late. The bite of the black mamba, known as the kiss of death, can kill a grown man in under an hour…the 13 year old girl never stood a chance (2).
Snakes. They terrify us and attract us at the same time. Since times immemorial, snakes have been a part of the human culture, both feared and revered. Their ability to strike down even the strongest among us inspires terror and respect. And yet, the healing power of their venoms has been recognized since ancient times. Indeed, how can something so deadly save lives? To answer that question, we must first clarify what snake venom is.
What is snake venom?
Snake venom is a modified saliva used in hunting and/or defense, which is injected into another organism and produces a toxic effect (3). It is made up of proteins and smaller peptides—which are responsible for most of the symptoms of envenomation—, carbohydrates, and other nonproteic compounds. Venom is designed to quickly immobilize or kill prey and predator. The components that make venom effective, called toxins, are very specialized, and have high biological activity (meaning they have a high capacity to affect our bodily functions). They can have an effect on many different body systems, including the central and peripheral nervous systems, and the cardiovascular system.
Snake venoms demonstrate a wide range of diversity. Composition can vary according to species, age, and geographical location. Differences have even been found between individuals in the same litter (4). Although not all sources of variation are understood, perhaps the most obvious one is diet, since venoms are specialized to target the snake’s preferred prey.
The genes that encode venom toxins can undergo rapid evolution, and thus permit snakes to adapt and consume a great variety of prey (3). In some cases the “arms race” between prey and predator can be clearly observed. For example, California ground squirrels are typically heavily hunted by Northern Pacific rattlesnakes. In response to this, squirrels have developed varying levels of resistance to rattlesnake venom. In areas where rattlesnakes are common, components in the blood of adult ground squirrels have been found to neutralize toxins in the snake venom. However, this resistance is lacking in squirrel populations living where rattlesnakes are not as common. To counter it’s prey’s resistance, rattlesnake venom and preying habits have had to adapt over the years (5).
Venom has evolved to attack and disable both predators and prey in a short amount of time. To do this, it contains toxins capable of identifying and attacking key targets that are responsible for the control of physiological processes. Often, these same targets are implicated in disease conditions. By studying the way toxins act, scientists can learn more about how our own systems work, and discover new targets in the development of cures for different diseases.
Because of the immense variability in venom composition, as well as the rapid evolution that venoms undergo, they are like a goldmine of potential drugs. Takacz and Nathan report that the diversity of venomous animals on Earth ranges from 100,000 to 170,000, representing more than 20 million toxins. Of those, only around 1000 have been carefully studied by scientists, and this has resulted in 15 different drugs. Animal venoms have a vast potential for the development of therapeutic drugs, which largely remains untapped.
Once a toxin has been identified for its potential medicinal effect, it can be either used as is, or it can serve as a template to create a mimetic compound. Mimetic compounds are molecules that are designed to behave in the same way as the original. They can have several advantages over the original molecules, including improved bioavailability, which can make it possible for them to be taken orally, since most venom toxins need to be injected. Moreover, the variation of venom composition between specimens makes producing a product of consistent quality through purification of toxins directly from crude venom, difficult. However, mimicking the complex structure of toxins is a challenging endeavor (3).
Venom toxins can be used in diagnostics, and as therapeutic agents. As of 2014, Takacs and Nathan reported 15 venom toxins used in diagnostics tests, all of them obtained from snake venoms. Out of the 15 therapeutic drugs derived from animal venoms, 8 of them come from snakes. Drugs derived from snake venoms are indicated for different medical conditions, including hypertension, cardiac failure, acute coronary syndrome, and acute cerebral infarction. They are also used as defibrinating agents and for the treatment of hemorrhage during surgery (3).
“Jararaca” by Felipe Süssekind/ CC BY 2.0 A toxin from the venom of the South American pitviper Bothrops jararaca was used to produce ACE inhibitors, a class of drugs used to lower blood pressure in patients with hypertension and heart disease.
Cobra venom factor (CVF) is a compound that has been used to reduce the chance of immunological rejection in transplant patients. It is found in the venom of different species of cobra, and acts by depleting the immune complement system (4).
Antibacterial properties have been observed in the venom of some snakes, including the inland taipan, considered to have the most toxic venom of all snakes. Also, two components of the venom of the king brown snake (Pseudechis australis) were found to be 70 and 17.5 times more effective than the antibiotic tetracycline in an in vitro assay (4).
Two interesting compounds that are currently being developed into therapeutic drugs by the company Theralpha are derived from hannalgesin from the king cobra (Ophiophagus hannah), and mambalgins. Both are part of the family of three-fingered peptides found in elapid venoms, and have an annalgesic effect greater to or similar to morphine, which is considered the gold standard in pain relief.
Mambalgins are peptides found in the venom of the Black Mamba (Dendroaspis polylepsis). What is especially interesting about these molecules is that they apparently act through an entirely different pathway than morphine, and lack the side effects of this drug, including creating tolerance (6).
Mambalgins work by inhibiting acid-sensing ion channels (ASICs) that are found on nociceptors. Nociceptors are neurons that sense pain stimuli. By interfering with the ASICs, mambalgins effectively block the sensation of pain. It is not clear why mambalgins are present in black mamba venom, but it has been suggested that their function is to prevent prey from fleeing (7).
An example of how similar toxins can have entirely different effects are two peptides present in the venom of the Texan coral snake, which also interact with ASICs. In this case, they overstimulate nociceptors by causing the ion channels to remain open. Overstimulation results in continuous pain signaling, which translates into the intense, burning pain which is a characteristic symptom of the bites of this snake (7;8).
How are venom toxins studied?
Observation of the effects of envenomation is one way in which potentially useful toxins can be identified. For example, when looking for compounds to help prevent blood clot formation, one could look for venoms that cause the blood to flow freely without clotting. However, a disadvantage of this approach is that compounds that are present in small concentrations might not contribute to the envenomation symptoms, and may be overlooked. A different approach is to screen a variety of venoms by dividing them into different fractions, and then testing out each fraction to observe its effects (4).
One of the main bottlenecks in the process of identifying useful snake toxins is the low volume of venom that can be obtained through milking. Milking is the process through which venom is extracted. It involves making the snake bite on a container and massaging its venom glands to help the venom flow. In a typical milking session, most medically relevant snakes produce around 100-200 mg of venom, with some very large snakes being able to produce up to more than a gram (4). This is a relatively straightforward, albeit very risky, procedure with front-fanged snakes like those of the cobra and viper families. However, with rear-fanged snakes, which have a less developed venom injection apparatus, venom is harder to extract.
The amount and ease with which venom can be milked is one of the reasons that, traditionally, venom screening has been relegated only to the venom of those snakes of medical importance. Rear-fanged members of the colubrid family were generally thought to have venoms of low toxicity (except for a few species, like the Boomslang), and because of this their venoms have not been so widely studied. However, scientists have realized that even though most of these snakes do not pose a threat to humans, they do produce potent toxins that can be of interest. However, the small amount of venom available still represents a challenge (4).
Typically, snake venom components are tested on mice. However, during the initial screening of numerous venom fractions, the large amounts of volume needed to treat mice may be prohibitive. For this reason, the use of other organisms, particularly zebrafish, has been proposed (4). The use of zebrafish has several advantages, including the much smaller volume of venom needed, as well as the possibility to observe how the toxins affect embryo development (thanks to their transparent eggs and embryos). The targets affected by snake toxins are largely conserved across many organisms (3), which means that although zebrafish will never be able to completely replace testing in mammals, they could be used for initial venom screening.
Another strategy that has improved the study of venom toxins is the creation of toxin libraries. Dr. Zoltan Takacs, a hungarian-born toxinologist that specializes in collecting and studying snake venoms, is the co-developer of the Designer Toxins technology. This is a tool designed to create libraries of toxins which are screened for action on a specific target. This makes it more efficient to identify potential therapeutic agents. Takacs is also the founder of the World Toxin Bank, which “is a biotechnology initiative exploring the toxin arsenal in Earth’s venomous animals for medical applications.”
Conclusion
Snake venoms represent a rich source of potential therapeutic agents. However, investigating their benefits involves hard and laborious work, including risky fieldwork. According to Dr. Takacs, it takes approximately 25 years since a toxin is first discovered to develop a drug for human use. Unfortunately, the populations of many species of snake have been dwindling over the last years (9). Snakes are considered undesirable by many, but perhaps we can gain a new perspective if we consider that loss of snake biodiversity also means loss of many possibly life-saving compounds.
If you want to learn more, you can check out the references:
