Good Radiation

This video is from cadamole, the artist who wrote A Biologist's Mother's Day Song. I'm pretty much loving everything this guy posts and this rap about public radio is no exception. As I do a lot of tedious lab work I listen to a lot of NPR, if you do too then you will love love love this!

Happy Earth Day!

Happy Earth Day, ya'll!

Today, April 22, marks the birth of the environmental movement in 1970 in the U.S. During the early 1960's the attitudes of many Americans concerning the environment began to change. No longer were they thinking of the Earth's natural resources as limitless and using them as without consequences. This was particularly evident with the controversy that erupted after the publishing of marine biologist Rachel Carson's Silent Spring in 1962. When the Apollo astronauts photographed the Earth from space in 1968 the image brought home the fragile nature of the planet. Close on the heals of this event was the 1969 industrial accident in Ohio Cuyahoga River, where the industrial runoff caught fire and spurred many to action. This action resulted in the U.S. Congress passing the National Environmental Policy Act (NEPA) that established a national policy that encouraged harmony between man and nature. The U.S. involvement in the war in Vietnam added yet another layer, no so much to the environment itself but instead challenging the status quo on public policy and human rights. When you boil it down, the environmental movement includes conservation and green politics and actions. It advocates for sustainable management through public policy and individual behavior. And while there is no central organizing force behind it there are various organizations, in a range of sizes, that promote awareness, work with local and national figures, and educate the public through events.

Earth Day started with Gaylord Nelson, a U.S., senator from Wisconsin. Nelson was a conversationalist who had witnessed the ravages of the massive 1969 oil spill in Santa Barbara, California, and was someone who knew how to inspire the youth of America into action. In late 1969, he announced there would be a national "environmental teach-in," which resulted in 20 million Americans taking to the streets, parks, and auditoriums to protest against oil spills, industrial pollution, raw sewage, toxic dumps, pesticides, habitat loss, and other environmental degradation. It was the first Earth Day event. It was a nationwide demonstration for concern for the environment involving thousands of schools and communities. It was followed by the creation of the U.S. Environmental Protection Agency (EPA) in 1970, then the Clean Air Act, then the Clean Water Act in 1972, and the Endangered Species Act in 1973. During this time new groups such as Greenpeace, formed in Canada in 1971, and existing organizations such as The Nature Conservancy, formed in 1951, the Sierra Club, and the National Audubon Society adopted and/or promoted these principles as well as bringing legal action against companies that destroyed the land and resources. By the late 1980's, individuals had gotten into the movement by living greener and establishing things like local recycling programs. Earth Day had a resurgence in the 1990's, this time it was global, with the participation of 200 million people and 141 countries. In 1992, at the United Nations Conference on Environmental Development (UNCED), or Earth Summit, an unprecedented number of governments and NGO's agreed on a program to promote sustainable development, and then U.S. President Bill Clinton was prompted to award the Medal of Freedom (the highest honor given to civilians in the U.S.) to Gaylord Nelson. In the early 2000's the environmental movement focused on global warming and clean energy, using the Internet or organize activists. Today we find ourselves embroiled in controversy once again with climate change deniers, lobbyists, reticent politicians, and a disinterested public. But concern by many for the environment and especially interest in green energy is keeping the movement alive.

Want to know more about Earth Day events near you, no matter what part of the world you live in? Check out the EPA's Earth Day page:
http://www.epa.gov/earthday/

Here are a few more Earth Day websites I recommend checking out:
http://act.earthday.org/
http://www.earthday.org/
http://earthday.envirolink.org/history.html

Learn more of the history behind Earth Day here:
http://www.earthday.org/earth-day-history-movement
http://www.wten.com/Global/story.asp?S=5963519

(image from healing.about.com)

A Catchy Tune

image from the Daily Mail, story linked below, credit to Alamy

 I heard a song in the car earlier today and now it's stuck in my head. I've been silently, and sometimes no so silently, singing it all day. So imagine my surprise when I was flipping, or rather clicking, through the most recent issue of Current Biology and this study all about the cultural transmission of humpback whale song caught my eye.

Cultural transmission. Put simply it is the social learning of information or behaviors within members of a species. In the animal kingdom you can find it in several large groups including cetaceans (whales and dolphins), birds, and primates. It can happen in a couple of different ways. Cultural traits can be passed vertically from parents to their offspring. They can be passed obliquely from older nonrelated individuals to younger individuals. And they can also be passed horizontally between unrelated individuals close to or within the same generation. Kinda makes sense right? I mean, where did you get your information as you grew up and where do you get it now?

The study for today's post takes a look at male humpback whales (Megaptera novaeangliae). This species is wide ranging, living in polar and tropical waters all over the globe, and they are known to migrate between northern and southern latitudes with the climatic cycle usually for feeding and reproduction. Humpback whales live in groups and are protective but not thought to be territorial. Both males and females will vocalize, but males produce long, loud, and often complex songs that function in sexual selection. It is known that whales within a population will sing the same song which will slowly change over time. This study looks at the horizontal transmission of these songs over the ocean basin.

Before discussing a paper about whale songs it is probably goon to note that the sounds of a song are arranged in a nested hierarchy: "themes" contain a number of repeated "phrases" which consist of a string of individual "units." In this study, the researchers picked field locations that corresponded to the multiple migration routes and breeding grounds within the western and central South Pacific region (northeastern Australia, New Caledonia, Tonga, American Samoa, the Cook Islands, and French Polynesia). Over an 11 year period they recorded humpback whale songs mostly using hydrophones suspended from boats. Then they viewed the songs as spectrographs so that they could look at each unit in the song clearly and then transcribe it based on the visual and aural qualities of the sound. The recorded sounds were classified and analyzed, comparing the similarity of songs and grouping all songs of the same type or themes together. The identified song types were grouped into six different lineages with color: pink, black/gray, blue, red, yellow, and green. When a song had comnpletely evolved and the orignial themes were replaced they were renamed/recolored. This made it easier to track the movement, evolution, and splits in song type between populations.

The study points out that at any one time males within a population show a strong conformity to a single song type containing the same themes sung in the same order. The pattern of the song evolves from year to year but all singers maintain conformity. When analyzing the songs they found that four new songs originating in eastern Australia gradually spread eastwards so that within two years the whales in French Polynesia were singing the same song. That is pretty fast over a really large area. Considering that, during the breeding season (July-October), there are several breeding groups where interchange is uncommon, what is going on?  The direction of the song transmission may be the detail that answers this question. The songs appear to have changed and radiated consistently from west to east in a series of cultural waves. One possible explanation for this directionality is that the eastern Australian population is the largest in the region and so its influence on the other populations is greater than the influence of the other populations on it. Another explanation is the migration. Males from different populations encounter each other along shared migration routes where they hear and learn each other's songs. Previous studies have shown that the eastern Australian population songs rapidly change, within two or three months, and so migratory routes would not need to overlap extensively and minimal contact would be required for song learning.

Overall, this study is a wonderful example of cultural transmission over a vast geographic area. The rate of change and the vocal linkage between populations is pretty incredible. Now I just need go get my next cultural wave of information to get this song out of my head.

Read the article here:
Garland, Ellen C. et al. (2011) Dynamic horizonal cultural transmission of humpback whale on at the ocean basin scale. Current Biology: 21, 1-5. (DOI: 10.1016/j.cub.2011.03.019)
The article and supplementary content includes audio recordings.

Visit the Whalesong  Project: http://www.whalesong.net/index.php

After some searching I found that this article has been picked up by some major news outlets, particularly in Australia:
http://www.smh.com.au/environment/whale-watch/word-of-mouth-spreads-whale-song-far-and-wide-20110415-1dh7o.html
http://www.radioaustralia.net.au/pacbeat/stories/201104/s3194046.htm
http://www.businessweek.com/lifestyle/content/healthday/651947.html
http://news.bbc.co.uk/earth/hi/earth_news/newsid_9457000/9457855.stm
http://www.nytimes.com/2011/04/19/science/19obwhale.html
http://www.dailymail.co.uk/sciencetech/article-1376862/Popular-humpback-whale-songs-spread-world-like-hit-singles.html

Resistant to Base

You're gonna have to face it, it's resistant to base!

Moving at a Snail's Pace

This post is about slime. Well, it's about moving around in slime. *squish*

Mollusca, or mollusks, is a large and highly diverse phylum of invertebrate animals. Within this phylum is the Class Gastropoda, or gastropods, which include snails and slugs. Generally, gastropods, specifically snails, have an asymmetrically spiral (coiled on one side) shell that functions as a portable retreat. Slugs are almost identical to snails except they lack a shell. The snail and slug body consists of a head, foot, and visceral sac/hump, and mantle (pallium). The head includes a mouth surrounded by one or two pairs of tentacles which often carry eyes and a pharynx containing coarse or fine teeth on the radula (like a tongue). The foot is the main locomotive organ and is usually the part that is visible outside of the shell. On the sole of the foot are mucus glands that secrete the slime that the gastropods crawl on.The visceral sac contains most of the inner organs and the mantle is a tissue fold covering it.

Though snails and slugs have no external extremities they are quite capable of moving around in their environment. Understanding this movement has been of interest to scientists and engineers for some time, even inspiring new classes of robotic movement and adhesive locomotion. It is known that a series of pulses of muscle contraction and relaxation traveling along the central part of the foot's ventral surface allows the snail to move forward, and only forward in terrestrial gastropods. The pulses of muscles are called pedal waves, the regions of the foot between pedal waves are called interwaves, and the distance between the two is called the wavelength. When these waves interact with the mucus secreted by the gastropod propulsive forces are transmitted to the ground. In describing snail locomotion, the number of waves is classified according to their number and direction. They are classified as a single train of pedal waves (monotaxic) or as a two (ditaxic) or four (tetrataxic) series of waves. It is also known that the crawling speed is directly proportional to the speed and frequency of the pedal waves.

A 2010 study in the Journal of Experimental Biology takes a look at the mechanism by which the propulsive forces are generated during gastropod locomotion. To accomplish this the researchers used a newly developed force-cytometry method where they calculate the spatial and temporal distribution of pedal forces from measurements of the deformation produced by the snail when it contacts a surface of known elastic properties. This allows them to study the movement is great detail. They can measure the horizontal traction stresses to the surface underneath the snail/slug without any interference with the animal's body. Neat. The study also analyzes the kinematics (motion without reference to the forces causing it) of the pedal waves and its significance of the generation of traction force. They did this to find the relationship between speed/wavelength and velocity, to determine if the waves maintain a constant speed/wavelength, to find how the snail accelerates and decelerates, and to see if a change in speed is accomplished by increasing the number of waves or by varying the speed/wavelength.


Fig. 1. from the paper showing the ventral surface of the banana slug

That all sounds very...complicated. So how do you measure the pedal waves of a snail's foot? If you know any biomechanists then you know they like to do two things - put animals on treadmills and put animals on transparent surfaces. In this case they tested banana slugs (Ariolimax californicus and A. buttoni), grey field slugs (Deroceras reticulatum), and garden snails (Helix aspersa) by placing them on transparent surfaces, illuminating them, and then recording them crawling with digital cameras. Turns out that if you illuminate the body in different ways you can get different information about movement. Add all of those ways together and you get a 3D reconstruction of the snail's foot as it moves.
The researchers found that when a snail/slug moves forward there are alternating pedal wave and interwave regions propagating from the tail forward to the head, but the interwaves remain stationary with respect to the ground. That result wasn't all that surprising, and agreed with previous studies. When they looked a little closer at the high-resolution images they found that the organization of the waves was not symmetrical and did not move at a constant speed. They observed steady wave acceleration followed by abrupt deceleration, a variable speed of pedal waves which modulated the magnitude of stresses under each wave. This was unexpected and observed in more than one of their test species, suggesting that the pattern is mechanically relevant to locomotion. They also found that the net forward force was generated beneath each stationary interwave. This is where the animal is pressing the foot against the ground and then pulling it backwards, propelling the body forwards. The foot is actually lifted during the pedal waves. Another result showed that that the crawling speed increased with pedal wave frequency. Not all that surprising, have more waves then move faster. And the mucus, we can't forget the mucus. This study's experiments showed that the slugs were able to move themselves over very thin threads of mucus without changing the pedal wave pattern or frequency. This suggests that the amount of pressure applied by the foot doesn't really matter for propulsion. Considering the rugged surfaces that snails and slugs move on that is not all that hard to believe.

The take home message? Mucus is helpful but it is the muscle movements that allow snails/slugs to crawl.

Read the study here, and there are videos in the supplemental materials:
Lai, J. H., J. C. del Alamo, J. Rodriguez-Rodriguez, J. C. Lasheras (2010) The mechanics of the adhesive locomotion of terrestrial gastropods. Journal of Experimental Biology: 213(22), 3920. (DOI: 10.1242/jeb.046706)

Get in Shape

Lately I've been reading papers on leaf morphology, and in the grand art of being lazy I decided to post about a paper I've already read rather than reading a whole new one.

I think that reading a paper about leaf morphology is kinda difficult if you don't know the basic parts of a leaf, and although this paper doesn't get into the itty-bitty differences in leaf structure I'm still gonna go through some of the basics. This is a leaf:

It consists of a (usually) flat photosynthetic portion called the blade where the very tip is called the apex, the edges the margins, and includes both a midvein and lateral or net veins. The margins of some leaves are serrated or have "teeth" with the low, in-between areas called the sinuses. At the base of the leaf the blade is attached to a supportive stalk called the petiole. Where the petiole and the stem meet is the stipule.

Morphology refers to the study of the forms of things and the relationships between their structures. In botany, leaf morphology is simply the characterization of leaf shape. The traits that you see on plants are determined by a combination of genetic heritage (genotype) and the capacity for a single genotype to respond to environmental variation (phenotypic plasticity). There has been quite a lot of research into the roles of genotype and plasticity in order to figure out how an organism responds to change. Studies such as these typically grow plants in a common garden experiment where all of the individuals are grown under exactly the same conditions so as to see what traits are different. These types of experiments show that in most species both plastic and genetic factors are important for a number of plant functions such as stomatal distributions, photosynthetic efficiency, leaf area, water availability etc. However, little is known about the plastic response of some leaf traits to temperature.Why does that matter? In terms of global climate change it is important to know both how plants responded to temperature in the past, using fossilized plants, and how they are responding to changing temperature now. And because many of these traits are plastic they can tell us a lot about rapid climate change. For example, it is known that in colder climates plants have more highly dissected leaves, meaning they have a low shape factor and a high compactness and perimeter ratio, and that many species show a temperature effect on leaf shape.

A paper from 2009, published in PLoS ONE, takes a look at leaf size and shape in Red Maple (Acer rubrum) growing in contrasting climates. They started by collecting seeds across a broad temperature gradient, across the eastern U.S. and Canada. Then two common garden experiments were set up in Rhode Island and Florida. These were common garden experiments in that they had the same set up in terms of plot layout, plant spacing, etc. but as they are in different locations there are differences in soil composition, precipitation, etc. Once the plants had grown then two leaves per plant were collected and the petioles removed, then they were dried, pressed, and photographed against a black background. The researchers used Photoshop to analyze their leaf images. They measured/counted the number of teeth, leaf area with teeth, and leaf area without teeth. They also measured a range of leaf size and shape variables using a program called ImageJ (very useful freeware from NIH that I use all the time). There were three categories of variables:

1. Leaf Dissection - Shape Factor: This was calculated as 4pi times the leaf area divided by the perimeter squared.
2. Compactness: This was calculated as the perimeter squared divided by the area.
3. Perimeter Ratio: This was calculated as the perimeter divided by the internal perimeter. The internal perimeter being without the teeth.

In this study, phenotypic plasticity was used analogously with growth site, and they found that growth site explained 5 to 19% of the variance they observed for traits related to the number of teeth on a leaf and the leaf dissection. They also found that seed source accounted for 69 to 87% of the variance. The plants from cold climates had more teeth, but smaller teeth, and were more highly dissected. The researchers concluded that while the size of the teeth is probably due to genetics, leaf dissection and tooth number likely respond plastically to their environment. These results are consistent with other studies that found a functional link between leaf teeth and climate. As the trees studied here were only grown for two years before sampling, this study shows that plants can respond quickly to environmental change. That is good news for paleobotanists who study leaf morphology in fossilized plants, it can give them an idea of the environmental conditions with greater resolution. However, it is important to note that plasticity isn't the only process that determines the distribution of leaf traits. Other process operate on slower timescales and include evolutionary changes within a population and species. Also, this study does not look at environmental factors such as the concentration of atmospheric carbon dioxide and the UV-impact plants receive.

If you would like to read this paper you can find it for free through PLoS ONE:

Royer, Dana L. Laura A. Meyerson, Kevin M. Robertson, and Jonathan M. Adams. (2009) Phenotypic plasticity of leaf shape along a temperature gradient in Acer rubrum. PLoS ONE: 4(10), e7653. (DOI: 10.1371/journal.pone.0007653)

(images from pendernursery.com and teacherbridge.org, respectively)

The Photosythesis Rap

Many of my botanist friends found this song/video to be entertaining. I'm sure you will too.