Tiny Ninjas, Big Bites (A Guest Post)

By Alexis Brauner

Venom isn’t just a weapon for snakes and spiders.

A smaller, more dangerous insect is in existence and falls into the realm of venomous creatures: the assassin bug. This little critter is part of a scientific family called Reduviidae, a group where all the members share the same characteristic of being an ambush predatory bug. They prey on invertebrates (animals that don’t have a spine), such as crickets and mealworms, by injecting venom into them.

An assasin bug. Source: Fir0002/Flagstaffotos at Wikimedia Commons.

Assassin bugs are believed to have two versions of venom – one for feeding and one for defense. Both types of venom are made up of more than 100 proteins, but what is unique about it is its ability to paralyze and liquify the inside of the prey. That’s right… liquify. The tissues of the prey turn into a jello-like substance that the assassin bug can then suck through a long tube on its mouth called the proboscis.

How is the venom able to do that?

First, let’s peek at the mechanisms that work to carry the venom through the body of the assassin bug and into its meal.

The venom apparatus of an assassin bug is made up of three main parts: secretory glands, a muscle-driven pump, and a venom channel. The three secretory glands (the anterior main gland, posterior main gland, and accessory gland) are in the thorax and abdomen of the assassin bug. These separate glands release a specific form of assassin bug venom depending on what situation the bug is facing. For example, the anterior main gland releases a form of venom that does not paralyze prey but is thought to be used as a defense mechanism, while the posterior main gland releases the deadly form of venom.

The venom apparatus of an assassin bug. Source: Walker, et. al, 2018, modified by Alexis Brauner

Once released, the venom then makes its way to a muscle-driven pump within the head of the bug. The pump fills with the available venom when the muscle contracts and is released once the muscle relaxes. Think of the venom pump as a clothes pin: when you push on the prongs, the pin opens, and you can put things in it to hold; once you let go of the prongs, the mouth of the pin closes, but now the prong end is open. In this example, your fingers are the muscle and the clothes pin is the pump with one end open at a time. The muscle relaxation releases the venom into the venom channel in the interlocking maxillary stylets (also known as the fangs) of the assassin bug. And then…

BOOM!

Venom is in the food or the foe.

And if it’s in the food, then the tissues of the prey turn into liquid. This liquification phenomenon is caused by enzymes in assassin bug venom called proteases. All enzymes catalyze, or speed up, chemical reactions; however, proteases are specialized enzymes that catalyze the destruction of proteins. This means that the assassin bug venom goes into the prey and the proteases are like Pac-Men with razor sharp teeth that grind up the primarily protein tissue at such a lightning fast speed that, within seconds, the prey is juice!

Scientists continue to research assassin bug venom to learn more about its components, but one thing is for sure: The extraordinary liquid weapon housed in such a small insect is why assassin bugs are tiny ninjas with big bites.


To learn more:

Walker, A., Madio, B., Jin, J., Undheim, E., Fry, B., King, G. (2017). Melt With This Kiss: Paralyzing and Liquefying Venom of The Assassin Bug Pristhesancus plagipennis (Hemiptera: Reduviidae). Mol Cell Proteomics, 16 (4), 552-566. DOI: 10.1074/mcp.M116.063321.

Walker, A., Mayhew, M., Jin, J., Herzig, V., Undheim, E., Sombke, A., Fry, B., Meritt, D., King, F. (2018). The assassin bug Pristhesancus plagipennis produces two distinct venoms in separate gland lumens. Nat Commun, 9, 755. DOI: 10.1038/s41467-018-03091-5

The Weirdest Animals on Earth: 12 Amazing Facts About Platypuses

What IS that? A photo by Stefan Kraft at Wikimedia Commons.

1. Platypuses are so strange, that when British scientists first encountered one, they thought it was a joke: A Governor of New South Wales, Australia, sent a platypus pelt and sketch to British scientists in 1798. Even in their first published scientific description of the species, biologists thought that this duck-beaked, beaver-bodied, web-footed specimen may be some Frankenstein-like creation stitched together as a hoax. But this is only the beginning of their oddities…

2. Platypuses are egg-laying mammals. Mammals are animals that have a backbone, are warm-blooded, and females produce milk for their young. Most females that nurse their young also carry their developing babies in their bodies and give birth to live young… But platypuses don’t play by those rules. Platypuses are monotremes, egg-laying mammals that include the platypus and four species of echidna. Most female mammals have two functional ovaries, but female platypuses, like most female birds, only have a functional left ovary. Once a year, a female platypus may produce a clutch of two or three small, leathery eggs (similar to reptile eggs), that develop in her uterus for 28 days. Because female platypuses don’t even have a vagina, when the eggs are ready, she lays them through her cloaca, an opening that serves for reproduction, peeing and pooping. (In fact, monotreme comes from the Greek for “one hole”). She then curls around them and incubates them for another 10 days until they hatch.

3. Platypuses sweat milk! Not only do female platypuses not have vaginas, they don’t have nipples either! Instead, lactating mothers ooze milk from pores in their skin, which pools in grooves on their bellies so the babies can lap it up. …And they’re not even embarrassed about it!

4. Adult platypuses are toothless. Baby platypuses (that is the actual technical term for them, by the way… not “puggles”, which would be way more fun) are born with teeth but they lose them around the time that they leave the breeding burrow. In their place are rigid-edged keratinized pads that they use as grinding plates. When they catch their prey (worms, bugs, shrimp, and even crayfish), they store it in their cheek pouches and carry it to the surface, where they use gravel to crush it in their toothless maw.

5. The platypus “duck bill” is a sensory organ used to detect electric fields. Muscles and neurons use electrical impulses to function, and these impulses can be detected by electroreceptors. Although common in shark and ray species, electroreception is rare in mammals, only having been discovered in monotremes and the Guiana dolphin. Platypuses have rows of around 40,000 electroreceptors on their highly sensitive bill, which they wave back and forth in the water, much like a hammerhead shark, to determine the location of their prey. It’s a good thing this sense is so sensitive, since they close their eyes, nose and ears every time they dive.

6. Platypuses don’t use their tails like beavers do. Whereas beavers use their large, flat, leathery tails for swimming and slapping the water to send signals, platypuses don’t use their tails for any of that. Platypuses have large, flat tails for storing fat in case of a food shortage. Unlike beaver tails, platypus tails are covered in fur, which the mothers use to snuggle with their incubating eggs.

A platypus ankle spur. Photo by E.Lonnon at Wikimedia Commons.

7. Male platypuses have venomous ankle spurs. Their venom is strong enough to kill small animals and to create excruciating pain in humans. Since only males have it and they produce more venom during the breeding season, we think its main function may be to compete for mates and breeding territories.

8. Platypuses are knuckle-walkers with a reptilian gait. Although they are well-built for swimming with their webbed feet and legs on the sides of their bodies, these traits make it quite awkward to get around on dry land. To walk, they pull in their webbing and walk on their knuckles, exposing their claws. Like reptiles and salamanders, platypuses flex their spines from side-to-side, supported by their sprawling legs.

9. Platypuses have unusually low body temperatures. As unusual as they are, platypuses are still mammals, which are defined, in part, by their ability to generate most of their own body heat with their metabolism. Platypuses do this as well, but whereas most mammals maintain body temperatures between 37-40 degrees C (99-104 degrees F), platypuses are happy with a body temperature of 32 degrees C (90 degrees F). This lower metabolism reduces the amount of calories they need to eat.

10. They have no stomach. Stomachs are specialized protein-digesting chambers of digestive tracts that contain protein-digesting enzymes and acids to activate them. Not all animals have them, but most carnivores do. The most common exceptions to this rule are fish… and platypuses. Why? We don’t know for sure, but many of these animals consume diets high in calcium carbonate, which is a natural antacid. If their own diet would constantly neutralize their stomach acid, then the stomach really isn’t going to do them any good anyway.

11. They have 10 sex chromosomes! Most mammals have two sex chromosomes, one from each parent. An individual that has two X chromosomes is usually female and an individual that has one X and one Y chromosome is usually male. Thus, female mammals pass along an X chromosome to each offspring and males can pass along an X or a Y. But platypuses are not content to be normal in any way…They have 10 sex chromosomes: 5 from mom and 5 from dad. All 5 chromosomes from mom are Xs, whereas a male sperm either contains 5 Xs or 5 Ys. Birds also have two sex chromosomes, but in birds, individuals with two of the same type are usually male and individuals with different chromosomes are usually female. Their system is called ZW, where the mammalian system is XY. The platypus X chromosome is more similar than the X chromosome of other mammals to the bird Z chromosome.

12. The platypus genome is as much of a hodgepodge as its body. Only 80% of the platypus’ genes are like other mammals. Some of their genes have only previously been found in birds, reptiles, fish, or amphibians.

To learn about more weird animals, go here.

References:

Scheich, H., Langner, G., Tidemann, C., Coles, R., & Guppy, A. (1986). Electroreception and electrolocation in platypus Nature, 319 (6052), 401-402 DOI: 10.1038/319401a0

Warren, W., Hillier, L., Marshall Graves, J., Birney, E., Ponting, C., Grützner, F., Belov, K., Miller, W., Clarke, L., Chinwalla, A., Yang, S., Heger, A., Locke, D., Miethke, P., Waters, P., Veyrunes, F., Fulton, L., Fulton, B., Graves, T., Wallis, J., Puente, X., López-Otín, C., Ordóñez, G., Eichler, E., Chen, L., Cheng, Z., Deakin, J., Alsop, A., Thompson, K., Kirby, P., Papenfuss, A., Wakefield, M., Olender, T., Lancet, D., Huttley, G., Smit, A., Pask, A., Temple-Smith, P., Batzer, M., Walker, J., Konkel, M., Harris, R., Whittington, C., Wong, E., Gemmell, N., Buschiazzo, E., Vargas Jentzsch, I., Merkel, A., Schmitz, J., Zemann, A., Churakov, G., Ole Kriegs, J., Brosius, J., Murchison, E., Sachidanandam, R., Smith, C., Hannon, G., Tsend-Ayush, E., McMillan, D., Attenborough, R., Rens, W., Ferguson-Smith, M., Lefèvre, C., Sharp, J., Nicholas, K., Ray, D., Kube, M., Reinhardt, R., Pringle, T., Taylor, J., Jones, R., Nixon, B., Dacheux, J., Niwa, H., Sekita, Y., Huang, X., Stark, A., Kheradpour, P., Kellis, M., Flicek, P., Chen, Y., Webber, C., Hardison, R., Nelson, J., Hallsworth-Pepin, K., Delehaunty, K., Markovic, C., Minx, P., Feng, Y., Kremitzki, C., Mitreva, M., Glasscock, J., Wylie, T., Wohldmann, P., Thiru, P., Nhan, M., Pohl, C., Smith, S., Hou, S., Renfree, M., Mardis, E., & Wilson, R. (2008). Genome analysis of the platypus reveals unique signatures of evolution Nature, 453 (7192), 175-183 DOI: 10.1038/nature06936