Articles

Every two months I'll be changing up the theme of our articles.  The theme for April and May 2013 is Cycles! Feel free to comment on what you read in the comment box below, or send me an email through the Feedback Page.  You'll be seeing more articles here as the month moves along!  And don't forget - if you want to read an article from a previous month, you can always download a pdf from the "Back Issues" page.  Enjoy!

May 5, 2013
It's Time for Cicada Mania!!!

www.cicadamania.com

You might be hearing whisperings of a storm brewing on the horizon...an invasion coming soon to the East Coast...a hoard of millions that will soon be upon us...that's right...it's time for the 17 year cicadas!!!  But don't worry - this is nothing to be frightened of because cicadas are incredible creatures - harmless - and even kind of cute.  AND, they have an incredibly interesting life cycle.  In fact, let's welcome our new insect overlords by learning a little something about them, shall we?

What is a cicada, anyway?

Cicadas are insects in the order Hemiptera, and in the families Cicadidae and Tettigarctidae.  In the United States, there are over 170 species of cicadas.  Cicadas can be annual, whereby they emerge every year (for example, those in the genus Tibicen).  Cicadas in the genus Magicicada are periodical, meaning that they emerge in great numbers every 13 or 17 years.  The groups of cicadas that emerge at the same time are known as broods.  This year, Brood II of Magicicada is expected to emerge all over the East Coast; the first time since 1996.  Billions of adult cicadas will grace us with their chirping hum starting right about now and will stay through July!

Take a look at this video to learn what to expect this summer:

What is the life cycle of a 17 year cicada?

The 17 year cicada starts out as a rice-shaped egg that is laid in a groove on a thin tree branch that the adult female cicada carves out using her ovipositor.  When the tiny little cicada (called a nymph) hatches, it uses its beak-like rostrum to drink fluid from plants.  After a period of time the nymph climbs down the tree, falls to the ground, burrows under the earth and feeds on tree roots for the next 17 years.  It goes through several nymph stages, or instars, during that time.  In its final year, as soon as the soil temperature reaches 64 degrees F, the final instar nymph crawls out of the ground and starts climbing the nearest tree.  On its journey up, it sheds its exoskeleton and emerges as an adult, or imago, cicada.  Adult cicadas hang out in trees and search for mates; the females lay eggs and the population dies after about a month.  But don't worry - there are plenty of eggs to keep the cycle going!

What do cicadas do when they've emerged?

A Tibicen cicada emerging in Ohio

Cicadas are really quite harmless to humans and other animals.  They have only sucking mouth parts and don't bite.  In fact, 17 year cicadas are quite docile - you can easily catch them and pick them up to observe their movements and anatomy.  This means that they are very susceptible to predation by birds and other animals; however, because they emerge in the billions, they basically "swamp" the predators - there is more than enough for predators to eat, and what is eaten doesn't really make a dent in the overall cicada population.  In fact, many predator species learn when their prey species will emerge so that they can time reproduction (for example) around an abundant food source.  However, one hypothesis as to why these cicadas appear every 13 or 17 years is that 13 and 17 are prime numbers, making it difficult for predators to predict their emergence.  So, even though these cicadas are docile and easily caught, they have used a couple of evolutionary tricks to avoid total predation:  1) safety in numbers, and 2) unpredictability.

After emergence, cicadas usually hang out for about a month until they die.  During this time, you'll see shed exoskeletons on the ground (and some in vegetation) and adult cicadas in the trees.  But before you see them, you'll hear them, as the males make a very loud chirping hum by flexing their tymbals, a drum-like organ found on their abdomens (listen to cicada songs here).  Females click their wings to make a different sound.  This noise can be extremely loud - in the U.S., the loudest cicada is Tibicen walkeri, and it can make sounds as loud as 108.9 decibels...that's as loud as a live rock band, a jet plane taking off, a garbage truck, or jackhammer (take your pick).  That's pretty loud!

Magicicada spp. - photo by Wikimedia Commons

Still want to know more about cicadas?

Most of the information I've gathered for this article came from a number of excellent websites dedicated to this incredible insect.  Please do take the time to visit any of the following for more information:

• Cicada Mania
• Magicicada.org
• Cicada Central
• 17 Year Cicadas Primed to Emerge (NPR News Story)

If you live on the East Coast and are expecting cicadas to emerge in your area this summer, how will you welcome them?  Please take pictures or video and share them here - I'd love to see them!


April 8, 2013
And the “Most Intriguing Cycle” Award goes to…

As a biologist, there are all kinds of cycles that I’ve learned about (and I’ll be honest, I’ve forgotten some cycles too…sorry, Krebs). Some of my favorite cycles are life cycles of various critters – aquatic insects are super cool, but so are frogs, butterflies – I love basically anything that features a metamorphosis at some point in its life. But what does life depend on? Well, a few different things, but one of the most basic ingredients is water. So what better way to kick off the “Cycles” issue of Brainy Girls than to talk about the water cycle?

What is the water cycle?

The water cycle is pretty simple upon first glance. I’m sure you learned about it in school, am I right? It looks something like this:

But when you start looking at each component of the water cycle in a little more detail, it gets a lot more complex, and begins to looks something like this (by the way, you can click on any of these graphics to enlarge them):

But even this is a simplification. The above picture doesn’t even begin to describe the amounts of water that are carried through the water cycle. For example, did you know that only 3 percent of the world’s water is fresh? The rest of it is saltwater, and is not suitable for consumption by humans and other terrestrial plants and animals. Further, of that 3% of water that is fresh, most of it is locked up as ice in glaciers and the polar regions – almost 70% of the freshwater! The rest is stored in groundwater, lakes, reservoirs and rivers. So you see, the amount of water we have to work with and that allows us to survive is highly limited.

Whether you have a lot of it or not enough, water is a necessity for human existence everywhere. However, the capacity in which we use water varies across nations.

 

Can you think of reasons why this might be so? Given our dependence upon the availability of clean freshwater, you’d think that we’d be pretty careful about how we treat our water supply, and ensure that the water cycle keeps functioning in a way that supports life, right? Well…

Impacts of humans on the water cycle:

Even though the water cycle is a primary driver of life on this planet, not to mention a major force in the shaping of our planet in general, the actions of human beings can have consequences for how the water cycle works. Here are just a few examples:

• Deforestation – Removal of large areas of forests reduces the amount of water that plants put back into the atmosphere through transpiration. Without this moisture, there can be less rainfall in the same or neighboring regions. Less moisture also causes the temperature to increase, and the deforested land may undergo a process called desertification. Additionally, rain that does fall on deforested land is subject to erosion, whereby water washes away soil and sediment, increasing turbidity downstream. This is often detrimental to aquatic communities.

• Development and urbanization – Similar to deforestation, native plant communities are removed with development, reducing the amount of moisture transpired into the atmosphere. However, with development, once permeable surfaces are now covered with impermeable structures such as pavement, asphalt and concrete that do not allow water to be absorbed by the earth. This reduces the rate that groundwater supplies are replenished, and causes flashy runoff events which can increase erosion and sedimentation.

• Water storage and regulation – by storing water in reservoirs and regulating river and stream flows, humans have impacted the amount of freshwater entering the oceans, resulting in a sea level decrease in some areas. Our actions have affected about 1% of the total annual streamflow, or about 10% of the volume of freshwater that we actually use.

• Global climate change and ocean salinities - Ocean salinities have changed since the 1950’s as a result of global climate change (i.e., dry areas getting drier and wet areas getting wetter); an indication of the “intensification” of the water cycle. Salinity can affect freshwater supplies, as well as have biological consequences (e.g., fish community composition – and human food supply - in ocean regions).

• Increasing the Greenhouse Effect - Water vapor is the most common greenhouse gas, and has the capacity to change global temperatures, especially in the presence of other greenhouse gasses such as CO2. As global temperatures increase, the amount of water vapor in the atmosphere also increases, altering cloud cover and weather patterns. This can result in precipitation in the form of more rain (and less snow, meaning less water from snowmelt in summers), earlier springs (which can cause problems for wildlife that depends upon specific environmental resources for reproduction and raising young), and increased drought frequency (which is bad news for people and animals who depend on scarce water supplies).

Why it matters to you:

Jeez, all that sounds like a bummer! But I’m not going to sugar-coat it – it is a bummer. Humans depend on clean water for crops, food production, drinking, cleaning, transportation and numerous other things. The “ecosystem services” that the water cycle provides (such as temperature and weather regulation) are priceless, not to mention critical for our survival. So what can we do to protect our freshwater supply and keep the water cycle functioning? The biggest single thing we can do is reduce our water footprint. You’d be surprised at how much water it takes to manufacture goods and produce food, especially meat. Take a look at a few examples:

Can you think of ways you can reduce the size of your water footprint? With just a few small changes, you can save a lot of water. Choose to drink tap water from a reusable bottle instead of buying plastic bottled water. Buy local goods instead of supplies and food that come from far away places. Incorporate more local fruit and vegetables into your diet and reduce the amount of meat that you eat. Want more ideas? Here are 12 ways to reduce your water footprint.

I hope you’ve found this article to be informative and that it has given you some ideas about the importance of water in your life and in the lives of others. Did you reduce your water footprint as a result of something you read? If so, leave a comment and let me know!