Tuesday, January 16, 2018

The Bed Bug’s Piercing Penis (A Guest Post)

A reposting of an article by Rachael Pahl on January 26, 2015.

Sex is a dangerous, but necessary, part of life. Across the animal kingdom, there are a multitude of things that can go wrong. You could be injured in a fight by someone who wants to steal your mate, or maybe your partner eats you because you’re taking too long. Either way, nature must have a pretty good reason for the traumatizing effects of sex.

A male bed bug traumatically inseminates a female. Image by
Rickard Ignell at the Swedish University of Agricultural Sciences
posted at Wikimedia Commons.

Bed bugs have a particularly risky way of having sex. When a male bed bug wants to mate, he will pierce the female’s abdomen with his penis (called a lanceolate) and release sperm directly into her body cavity. Talk about forceful! This mode of reproduction in bed bugs is known as traumatic insemination; aptly named.

With what seems like a horrific way of reproducing, it’s hard to imagine that there are any benefits for the female. I’m sure you can come up with a plethora of things that could go wrong: infection, damage of major organs, bleeding, even death. Researchers Ted Morrow and Göran Arnqvist with Uppsala University in Sweden, argue that the female has a counter-adaptation to this antagonistic strategy. The area of the abdomen that the male pierces has been modified into a pocket lined with specialized tissues to prevent serious damage to the female. This area is termed the spermalege. Edward and Göran hypothesized that sex is not harmful to the female if the spermalege is punctured, but can be dangerous if any other area is pierced. They also hypothesized that more mating occurrences and improper punctures would reduce the lifespan of the female.

To test their hypotheses, Edward and Göran observed the number of times a female was inseminated and where she was pierced (on the spermalege or somewhere else). They had two set-ups to observe mating rate: (1) a female was placed with four males where lots of mating would take place and (2) a female was placed with four males, three of which had their penis glued to their abdomen so that they could not mate. These two set-ups allowed the researchers to observe the differences in female life span between those who had a high mating rate and those who had a low mating rate. Then, the researchers wanted to see where the female was being pierced and how that affected her life span. In addition to traumatic insemination by male bed bugs, the researchers used a pin to pierce the spermalege or an area outside the spermalege and then compared the damage.

The study produced two big results. First, females who mated more had a shorter lifespan than those who mated less. This was because the sperm and other fluids deposited caused an immune response as they were seen as foreign objects; too much of these foreign substances can have negative effects on the organism. Second, females that were pierced through the spermalege lived longer than those who were pierced outside the spermalege, suggesting that the spermalege functions to reduce damage and/or infection during insemination.

So what are the benefits of traumatic insemination and how does the spermalege reduce the costs to the female? Well, there is a lot of paternal ambiguity in the animal kingdom. The direct deposition of sperm into the abdomen may ensure paternity by getting the sperm as close to the ovaries as possible before another male bed bug can mate with her. This method also reduces courtship time and avoids female resistance, meaning that other males may not have the chance to steal the female away. The spermalege protects females from traumatic insemination by localizing damage to one area that can easily repair itself. Since the spermalege is lined with cuticle, it prevents the leakage of blood and sperm from the wound. The spermalege may also function to prevent entry of pathogens into the bloodstream. In the end, this traumatic insemination is no more dangerous than any other kind of sex, however painful and horrible it sounds. It may even be less risky if done correctly.


For more information, check out:

Morrow, E., & Arnqvist, G. (2003). Costly traumatic insemination and a female counter-adaptation in bed bugs Proceedings of the Royal Society B: Biological Sciences, 270 (1531), 2377-2381 DOI: 10.1098/rspb.2003.2514

Tuesday, December 19, 2017

Reindeer Games: 8 Surprising Facts About Reindeer

A Swedish reindeer watches you. Photo by Alexandre Buisse at Wikimedia Commons.

1. Reindeer are caribou (kinda): Reindeer are the same species as caribou (with the scientific name Rangifer tarandus), but the terms are not completely interchangeable. Rangifer tarandus is a species of deer that is native to Northern regions of Europe, Siberia and North America, which includes many different habitat types, like arctic, subarctic, tundra, snow forest and mountains. These variations in harsh environments have led to variations among populations, resulting in multiple subspecies. The Rangifer tarandus subspecies that live in North America are commonly called caribou and the subspecies that live in Europe and Siberia are commonly called reindeer. We also often refer to domesticated populations as reindeer, regardless of where they are.

A map of reindeer and caribou distributions. Image by TBjornstad at Wikimedia Commons.

2. Rudolf’s red nose was an adaptation: Technically, reindeer don’t have red noses, but they do have lots extra blood flow in them. The inside of their noses are twisted and vascularized so the warm blood can heat up the frigid Arctic air before it gets into the lungs.

3. Santa’s reindeer were probably girls: Not only do reindeer have the biggest antlers of all deer species (relative to body size), but they are the only deer species in which both males and females grow antlers. Both males and females use their antlers to scrape through the snow and look for food, but males also use their antlers to compete with one another and impress the ladies during the breeding season. Unlike horns, antlers shed and regrow every year, and this process is regulated by sex hormones. When the new antlers grow in spring, they are made up of cartilage and lots of blood vessels and are covered in a furry skin called velvet. The blood carries lots of calcium into the antlers, which helps them to grow and harden into bone. When testosterone levels drop in males at the end of their breeding season in early December, their antlers fall off. Females, however, generally keep their antlers until March or April. So, if Santa’s reindeer had antlers at the end of December, they were probably female!

4. If you’re going to pick an animal to travel the world in one night, reindeer are a good choice: Some North American caribou migrate over 3,000 miles a year (more than any other land mammal). They can run up to 50 miles per hour and swim over 6 miles per hour. Migration herds can be up to 500,000 animals and baby reindeer learn to run within two hours of birth!

A swimming caribou herd. Photo by Lestar Kovac at Wikimedia Commons.

5. Reindeer eat weird stuff: Like cows, reindeer are ruminants, which means their stomachs have multiple compartments, some of which specialize in maintaining microbial communities to help them digest. Unlike cows, reindeer predominantly eat lichen, which are combinations of algae and fungi that are typically high in carbohydrates and low in proteins. To make up for this low amount of protein in their diet, reindeer may occasionally eat rodents and bird eggs.

6. They have the coolest feet: Their hooves have four toes: two that splay out like snow shoes and two dew claws. Their hooves have sharp edges to dig for food and are paddle-shaped for swimming. Their hooves even change with the seasons to provide the best traction, being softer in the summer when the ground is soft and hard in the winter to walk on slippery snow and ice.

7. Some reindeer use clicking knees to communicate: Some subspecies have knees that click when tendons slip over bone extensions in their feet. They use this sound to stay with their herd, even when weather conditions limit visibility. But because larger reindeer have larger legs and therefore make louder knee-clicks, they also use these sounds to establish dominance.

8. Reindeer are the only mammals that can see UV light: They have a reflective layer in the back of their eyes that is golden in summer and blue in winter. When it is blue, this allows reindeer to see contrasts in UV light, such as lichen (which absorbs UV) versus snow (which reflects UV).

Tuesday, December 12, 2017

The Truth Behind Those Sleeping Bears (A Guest Post)

A reposting of an article by Tabitha Starjnski-Schneider on December 8, 2014.


Name some animals that hibernate.

Was the first one mentioned a bear? That’s understandable…you were probably told that bears go to sleep shortly before winter, stay asleep the entire winter, and wake up in early spring.

What if I told you that your teachers lied to you, and that bears don’t actually hibernate?! Not a true hibernation, at least.

For an animal to be considered a true hibernator, it actually needs to stay in a sleep state for months at a time (like during an entire season), but also lower its body temperature far below where most other animals barely survive. Such an animal thus hibernates by lowering its metabolism, dropping its body temperature, and passing, most commonly, much of the winter in this Rip Van Winkle state. The many challenges of enduring a long and strenuous season such as winter, while "sleeping" it away, are complicated, but here we talk about just a couple.

Something your teacher may have also told you was that bears are mammals, and therefore are "warm-blooded". That seems a little silly; all animals with blood are going to have warm blood. Bears are actually called endothermic, meaning they don’t have to rely on warming or cooling their bodies by outside forces such as the sun. While undergoing this sleep-state, bears possess internal and external temperature control. These animals slightly lower their heart rate and body temperature internally and minimize their external movements in an effort to save energy and conserve heat. Of course these periods of reduced heart rate, temperature and inactivity don’t actually last all winter, as with true hibernation, but only a few weeks at a time. This overall ability and state is called torpor, not true hibernation. And although there is debate over the definitions of each, most researchers believe there is enough of a difference to categorize them separately (like cat naps versus comas).

One of the reasons for taking these naps is as basic as why we grocery shop. When the environment changes in such a way that doesn’t suit an animal (i.e. an empty fridge), they can better survive by conserving energy and going inactive until food returns. Before napping however, each adult bear will begin to dig a den, hollow out a tree trunk, and/or find a cave to prepare for winter. Once tucked away in their little beds, they use these dens like a Thermos, retaining as much of their body heat as possible. For the most part, these giants go to sleep for a few weeks at a time, wake up to warm their bodies some, then fall back asleep. This occurs over the course of a winter season until spring arrives and the bear can reemerge into the re-warmed world outside.

There is another, more important reason why these bears slumber though. After breeding in spring/summer, these mammals begin their fall-time buffet, eating foods high in carbohydrates and fat to gain as much weight as possible. Why you ask? So that the mothers gain enough fat and energy to develop, birth, and feed their young while in the winter hideaways. Ever see the videos of polar bears emerging with their cubs from a snowy fortress in the side of a hill?


Now how could they ever give birth if they were sleeping the whole time? It’s the same with black bears and grizzly bears, for that matter.

It all sounds pretty cool right? These mama bears should be given a medal for their dedication. And the next time someone refers to bears hibernating, you can assuredly respond that they actually enter a state of torpor, or winter-long cat naps.

Tuesday, December 5, 2017

Why Reptiles Won't Wear Fur

A reposting of an article from September 19, 2012.

Have you ever seen a furry lizard? A fuzzy snake? A wooly turtle? Me neither. That's because a reptile in a permanent fur coat would whither like Superman with a pocket full of kryptonite. But why? Other animals are so content in their soft, luxurious layers... Why can't reptiles be?


"I wouldn't be caught dead in that fur coat you're wearing". Photo by Naypong at freedigitalphotos.net.
Animals exchange heat with their environments in four major ways: conduction, convection, radiation and evaporation:

  • Conduction is when heat moves from a hotter area to a colder area across a still surface. If you stand barefoot on a cold sidewalk, the heat in your feet is going to transfer to the cooler surface of the sidewalk by conduction and you will get cooler (which is nice in the hot summer, but uncomfortable when the weather starts to get chilly). Conduction can happen when the body is in contact with a solid (like a sidewalk), a liquid (like a bath), or a gas (like the air around you).
  • Convection is essentially conduction with movement, and this movement makes the transfer of heat even faster. If you are standing inside and it is 70ºF in the building, you will likely be fairly comfortable. But if you are outside on a windy 70º day, even though the environment is the same temperature, you will get colder faster.
  • We are all familiar with the warming effects of the sun's radiation, but in reality, all objects give off electromagnetic radiation. Radiation within the visible spectrum we perceive as colored light, but most radiation is outside our visible range.
  • Evaporation happens when water (like sweat or moist breath) converts from a liquid state to a gaseous state, taking heat away from the body. Animals are always in contact with something (like surfaces, air, or water), so conduction is always occurring.
The speed at which an animal's body heats or cools depends on the temperature difference between the animal's body and its environment. That is, in a very cold environment, an animal will cool quickly and in a very hot environment, an animal will heat up quickly, whereas in an environment that is close to the animal's body temperature, the animal will heat or cool very slowly. To put this in mathematical terms, let's call the animal's body temperature Tb and the environmental temperature Te. The bigger (Tb-Te), the faster the animal will cool. And the bigger (Te-Tb), the faster the animal will heat up. This difference between Tb and Te (in either direction) is called the driving force of heat exchange.

Imagine this circle is an animal's body, Tb is the animal's body temperature and
Te is the environmental temperature. The bigger (Tb-Te), the faster the
animal will lose heat and cool down.

This works the other way around, too.
The bigger (Te-Tb), the faster the animal will heat up.


What happens if you put fur on that animal? Now you can imagine this animal as having two separate layers, a body (with the temperature Tb) and an insulation layer (with the temperature Ti). Now for heat to be exchanged, it has to be conducted twice, once between the environment and the insulation, and again between the insulation and the animal's body. Ti is always going to be some intermediate temperature between Tb and Te and so the driving force of heat exchange will be much lower and the animal will heat up or cool down much more slowly. The thicker this insulation layer, the more stable Ti becomes and heat exchange happens even more slowly. Also, because insulation prevents movement at the body's surface, insulation layers eliminate any heat exchange at the body's surface (but not the surface of the insulation layer) by convection. (By the way, this logic also holds true if the animal has feathers or blubber or even a winter coat).

This inside circle represents an animal's body and the outside circle shows its insulation
layer. Tb is the animal's body temperature, Te is the environmental temperature and Ti is
the insulation temperature. Ti is always between Tb and Te, so the driving force of
heat exchange is reduced and the animal's body temperature does not change quickly
at all, even if the environmental temperature is extreme.

Most animals that have fur are mammals, as are most animals with blubber layers (like seals and whales) and animals that wear coats (like people and Paris Hilton purse dogs) and most animals with feathers are birds. What do these insulated mammals and birds have in common? They are endotherms. They generate most of their own body heat. This means that by slowing the exchange of heat between the animal's body and environment, the animal is provided with more time to generate heat and the insulation then helps to preserve this heat.

But reptiles (as well as amphibians and fish) are ectotherms. They get almost all of their heat from their environments. They maintain their body temperatures behaviorally, by choosing what environment to hang out in and what position to put their body in. If they are cold, they go bask in the sun to absorb radiation heat or lay on a warmed rock to absorb conducted heat. If they are hot, they lay on a cool rock in the shade to lose heat by conduction or soak in a cool stream to lose heat by convection. To maintain a relatively constant body temperature, they are constantly moving between warm and cool areas to adjust their body temperature one direction or another.

Many ectotherms rely on their ability to adjust their body temperatures quickly, and this ability depends on creating large driving forces of heat exchange. If an ectothermic reptile were to have an insulation layer, like fur, it would reduce its ability to adjust its body temperature by conduction and convection. It would lose its heat slowly and not be able to replace it fast enough. In the end, it would become too cold. It may seem paradoxical, but a lizard in a fur coat would likely die of cold-related physical issues (if not embarrassment).

Interestingly enough, just because lizards don't have fur doesn't mean they couldn't have hair. In fact, some of them do have hair, but not how you may think. Hair, fur, feathers, and scales are all made up in large part by keratin proteins. Many gecko species are well known for their wide, sticky toes that help them climb smooth, vertical surfaces (like walls). Their secret? Ultra-thin keratin hairs growing out of the geckos' feet provide a chemical adhesive force to keep the animal secured to the wall surface. So reptiles may not have a need for fur, but some of them have an innovative use for hair.

Want to know more about hairy geckos?

Autumn K, Liang YA, Hsieh ST, Zesch W, Chan WP, Kenny TW, Fearing R, & Full RJ (2000). Adhesive force of a single gecko foot-hair. Nature, 405 (6787), 681-5 PMID: 10864324

Wednesday, November 22, 2017

Eye Didn’t See That

By Evan Hovey

A grandmother and her grandson watching the television.
The elder is straining to see while the young man is not having any troubles.
Photo by Evan Hovey.

It’s Thanksgiving and the family just finished stuffing their faces full of turkey and cranberry fluff. Everyone meanders into the living room to sit down, let the tryptophan sink in, and watch some football. As you sit there, you start to observe the older family members around you take out their glasses or bifocals and squint towards the television in attempts to see what is going on. You begin to ponder the thought, “am I going to start to lose my eye sight as well?” Well, as it turns out, as you age, the number of cells that respond to light and color (called photoreceptors) begins to decrease.

Songhomitra Panda-Jonas, Jost Jonas, and Martha Jakobczyk-Zmija at the University of Erlangen-Nurnberg, Germany, looked into the number of photoreceptors in the retina of the eye to determine whether there was a loss as you age. The retina is the thin layer of tissue that lines the back of the eye. It is the location where your eye transfers what you see to the brain. There are two different kinds of photoreceptors in your eyes: rods and cones. Rods are those that detect light at low levels, which is what helps us see at night. Cones, on the contrary, are those that take in high light levels and help decode color. The authors believed that there would be a decrease in both kinds of photoreceptors as the eye got older (the older the person, the fewer photoreceptors). They came up with this hypothesis in part because of prior knowledge of a loss of tissue associated with vision in other parts of the eye as you age.

The researchers approached this study by obtaining fifty-five eyes from human donors that died at ages ranging from 18-85. The eyes were removed from the bodies less than eleven hours after death. Then the eyes were cut open and tissue samples from the retina were obtained. To determine the amount of photoreceptors in the tissue samples, the researchers used an ultrasound to view the retina and counted the photoreceptors on a photograph taken with the ultrasound. The two different kinds of cells were distinguished by their sizes (the larger cells were the cones and the smaller cells were the rods).

The results they found were as expected: the older you get, the fewer photoreceptors you have and the worse your eyesight is. The decline of the number of photoreceptors was at a constant rate throughout all ages of life. However, the number of rods declined faster than the number of cones. The loss of these photoreceptors causes you to view things with more difficulty. As your rods die, you begin to develop night blindness (the inability to see well in poor lighting or darkness). When your cones die, you begin to lose more of your visual perception, which includes straining when looking at something from a distance, as well as affecting how you see fine detail such as reading a book or looking at a television. The combined loss of your rods and cones is part of what causes older individuals to have more vision problems.

As you progress through life, your photoreceptors decline, causing your vision to get worse. As you sit down after Thanksgiving to enjoy some good old-fashioned fall football and the elderly people strain to see the television, you now know that the oldest person in your family is most likely having the hardest time seeing that big touchdown.


If you would like to read the actual paper, the source is located below:

Panda-Jonas, S., Jonas J., Jakobczyk-Zmija, M. (1995). Retinal photoreceptor density decreases with age: Ophthalmology, 102 (12), 1853-1859