Friday, August 8, 2014
Note: This show first aired on August 9, 2014.
Today we kick off Funathon here at WERU, the time when the station after months of giving and giving, asks for a little back. And the case that I want to make today, is that this is an entirely natural situation.
The typical view of nature is that of an adversarial relationship, think predator and prey, “survival of the fittest”, “nature red in tooth and claw”, its what most of us learned in school, and you could even go so far as to say our entire culture is built around this idea. Organisms compete for resources, those that get the resources win and go on living, those that don’t lose, and die. It’s a tough world out there, and it is, but there is more to the story than constant fighting over limited resources, in fact that is only a small chapter in the story of nature. In reality the main plot line goes something like this: I have a lot of something you need. You have a lot of something I need. Perhaps we should get together and share, and make both of our lives stronger as a result.
This kind of relationship is a form of symbiosis, called mutualism, and though it doesn’t get much press in science class, it makes much of what we experience in the natural world and in our own bodies, possible. It makes us possible. You may have heard about the legume family hosting bacteria in their roots that allow them to fix gaseous nitrogen from the atmosphere into a bioavailable form, essentially they make their own fertilizer. Or better put, they provide the habitat for a bacteria that makes the fertilizer for them. The bacteria gets a safe place to live, the legume gets the nitrogen it needs, both parties increase their fitness and win. The same thing is happening in your body right now. In your gut are bacteria that are synthesizing essential nutrients, things you can’t get out of the food you eat yourself, but that can only come from the work of the microbes in your intestines. You provide a nice place for these bacteria to live, and a steady supply of food, and in return they synthesize vitamins for us. Win win. If you want to get away from bacteria, we can look at examples from other realms of life. Some 95% of plant families, including 80 % of plant species form relationships with fungal partners. These are mycorrhizal relationships, the filaments of the fungus intertwine and sometimes even invade the plant root cells and it can be hard to identify where one ends and the other begins. The fungus provides water and minerals from the soil to the plant, in return the plant provides simple carbohydrates to the fungus. Both are enriched by the relationship. The various animal mediated pollination strategies of flowering plants provide yet another example of mutualism in nature, the animals provide a service to the plant (pollination, or moving plant genetic material from individual to individual) and in most cases, the plant provides a material reward to the pollinating animal, in the form of nectar or protein rich excess pollen. We don’t even have time to talk about lichen.
The point of this, and there is a point, is that as listeners, your relationship with WERU is mutualistic. This radio station provides its listeners with a service, many services in fact, you know what they are, and you’ll be hearing reminders about them in the coming week. In nature, there is no such thing as a one way relationship, and that is true of radio stations as well. You give up a tiny piece of your soul when you listen to the incessant advertising of commercial radio, at least in my opinion. With WERU the give back is so much easier, its like the fungus in the soil, spreading unseen everywhere, providing water and a wide variety of minerals and nutrients to the plants (that’s you dear listener) that make up our community. In return for the service the station provides, call us up and pledge your own little bit of simple carbohydrates. Just as in nature, both parties, the station and the community, are stronger as a result of this relationship.
Survey article on mycorrhizal relationships in plants: Wang, B 2006 “Phylogenetic distribution and evolution of mycorrhizas in land plants” Mycorrhiza 16 (5) http://link.springer.com/article/10.1007%2Fs00572-005-0033-6?LI=true
Note: This program first aired on August 2, 2014.
This week’s show is dedicated to WERU’s own News Editor, Amy Browne. I happen to know, from social media, just how she feels about the animal we are going to talk about today, though I also know from experience, she’s not alone.
The animal, the bane of existence for so many people, and so many companion animals this time of year, is the deer fly. The common name Deer fly refers to a group of animals in the genus Chrysops, of which there are about 100 species in North America alone. Deer flies are in the insect order Diptera, with all the other flies, in this case their common name is not a trick. It is the females that cause us so much grief. They require a blood meal from a vertebrate to ensure viability of their eggs. Males sip nectar from flowers, (like male mosquitos) for their sustenance. Deer flies (and their closely related bretheren Horse flies) are universally referred to in the literature as having “knife like” mouth parts. They achieve the required blood meal by slashing away at the flesh of the victim, causing a generalized bleeding, which they then slop up with their “sponge like” mouth parts. This part of the story you know well, if you spend any time outside in Maine in the summer.
I wanted to know more about these extremely annoying creatures, so I dug in a bit to see what I could find. And it turns out it is much as I suspected. They are hydrobionts, meaning they need wet areas in which to breed. The females, after their blood meal, lay their eggs on the underside of leaves in the understory or in swamp areas, above damp or wet ground. When the eggs hatch the larvae that emerge drop into the wet ground below and burrow in, living on detritus or as predators of smaller insects and worms. The larvae are active all winter, below the frost line apparently, and after feeding all winter they apparently pupate in early spring for a few weeks. The adults emerge in summer and live from one to two months, tormenting me and Amy Browne and our dogs, and anyone else foolish enough to be outside in wet areas when the temperature is warm enough. One of the sources I found indicated a minimum temperature range of 72 degrees F, but I know that to be incorrect, at least for the deer flies here in Maine. If I can get out before the temperature hits 60 degrees I know I will miss most of them, but above that, they are good to go. They are also primarily visual predators, attracted first and foremost to dark objects that move. If I wear a light colored shirt on my morning run I am much less bothered. My large black thin coated dog however, has no such choice. Sources say that scent and other biological cues like carbon dioxide are also attractants, but my experience leads me to believe the idea that they are primarily visual. It seems that their job in this world is to bite, and bite well, much to our chagrin.
Isn’t that the job of every animal? Every organism? To do whatever it can to carry on and pass on its genes? It is easy to disparage a biting insect that bothers us for one to two months a year, but we have to remember that everything has a job in an ecosystem. The job of many of the deer fly eggs is to get parasitized by wasps. The job of many deer fly larvae is to get invaded by bacteria and fungus and other microbial parasites. The job of many an adult deer fly is to get eaten by swallows and flycatchers and predatory insects like dragon flies and hornets. The job of the ones that survive is to reproduce, and to do that, they need us, or our dogs, or our livestock, or more likely, the large vertebrates that populate the north woods.
No body likes hanging out with deer flies. But all the same, I prefer a world where they exist, a world as full as it can be with as many different kinds of organisms as possible, a world rich and damp and squirming with life. That is truly the point of it all, and we can’t do it without the biters and scratcher anymore than we can do without the cute furry babies and the fluffy little birds. They all count, every last knife like mouthpart wielding one.
More good stuff from Bug Guide: http://bugguide.net/node/view/11387/bgpage
Here’s a whole bulletin about them from the Maine Forest Service: http://library.umaine.edu/MaineAES/TechnicalBulletin/tb160.pdf
Note: This program first aired on July 26, 2014.
A few weeks ago, I mentioned some of the butterflies I’ve been seeing around; right now its all fritillaries and sulphurs, earlier this summer is was Swallowtails, the Mourning Cloaks were earlier still this spring. Later in the summer I hope to see some Monarchs. Have you ever wondered why some butterflies are around at certain times but not others? Why are the Mourning Cloaks the first ones here in the spring, and then they disappear? Why are we seeing the fritillaries in such abundance now? Have you even noticed that there is a pattern to the appearance of different butterflies? Believe it or not, it’s not random happenstance. The answer is due to the fact that although we’ve all watched the Discovery Channel and think we have the butterfly life cycle down pat, it’s much more complicated and interesting than egg, larva, pupa and adult.
The truth is, butterflies are short lived creatures that come in seasons based on their life histories. Though it is hard to remember now in the thick of the heat of summer, the main obstacle to all arthropods is the cold of winter. Being primarily ectothermic or at the mercy of the external environment for temperatures favorable for metabolism and activity means that most insects have a difficult time being active in the winter here in Maine. The question facing butterflies, and all arthropods, is how to deal with winter. There are two main choices, the same ones we humans face, you can stick it out here in some kind of overwintering dormancy, or you can get the heck out of Dodge and migrate to warmer climes.
Migration is not the most common butterfly strategy for dealing with winter, and it’s easy to speculate on why. First, only the adults could possibly travel far enough, how much ground can a caterpillar really cover? Secondly adults don’t tend to live very long, we’re talking about live spans of days to weeks in most cases. Thirdly, and this is pure bias and subjectivity on my part, butterflies seem so fragile, so wispy. I can barely believe that tiny birds migrate successfully thousands of miles, but something as insubstantial as a butterfly? The best known of the migrating butterflies is of course the Monarch, and the details of just how they do it is still a huge mystery. What is known is that it takes multiple generations for them to complete the migration. The ones that leave here are not the same ones that return the next year. The ones that return are the great or great great grandchildren of last year’s butterflies.
So then, migration happens but is uncommon, and the timing of the return of the migrators depends on many factors, weather and conditions not only here but everywhere along their route, which can be thousands of miles. For those butterflies that stay here year round, the majority of them, they face a choice as well. We know that the basic butterfly life cycle includes an egg, a larval stage, a pupa stage and an adult stage. Which stage is the best one in which to wait out the winter? If you thought there was a clear cut answer to that, you haven’t spent much time studying evolution. The answer is of course, all of them. Different species have evolved different tactics for dealing with winter, mainly guided by coevolution with their host plant, the thing the larva or “eating stage” of the insect, lives on.
Mourning Cloaks are the first butterflies we see in the spring, and the reason for this is that they over winter as adults. They hide out under bark or in the leaf litter, emerge on the first warm days in early spring, mate and die. We see them again in the fall when the new generation emerges from a period of summer dormancy, fattens up on nectar and prepares to over winter. The Swallowtails we see in June by contrast, after the Mourning Cloaks are all gone, have over wintered as pupae, often attached to the trunks of trees. Their larvae spend the summer feeding on the leaves of various deciduous trees, and the last instar forms the chrystalis in time for winter’s cold. The fritillaries flying about now started out last year as an egg laid in late summer, near a patch of dead violets. The egg hatched and the tiny larva that emerged, the first instar, is what over wintered, without eating. This spring, when the violets emerged as a spring wild flower, the fritillary larvae were already there, ready to start feeding. Each of these butterfly species positions itself to be ready to make full use of its favorite larval food, and these plant foods in turn, have their own seasons, thus so do the butterflies.
Watch nature long enough and it becomes a giant game of connect the dots. The more you play, the more you learn, and the more you realize there is to learn. Play long enough, and you realize all the dots are connected.
Canadian reference on Mourning Cloaks http://www.naturenorth.com/spring/bug/mcloak/Fmcloak.html
Note: This program first aired on July 19, 2014.
One of my stated goals for this summer is to read. Reading is a deep pleasure for me, one I am not able to do as freely as I would like during the school year, and I have come to realize that if you want to read a lot, you have to consciously make time for it, thus my summer goal.
I want to share with you today one of the books from the first half of my summer, and it’s not your typical beach read, though I think many listeners might find it very interesting. The book is David Quammen’s Spillover: Animal Infections and the Next Human Pandemic. Quammen is a frequent contributor to National Geographic, which funded much of the research for this book, and author of several works of fiction and non fiction, the most well known of which is probably Song of the Dodo. Spillover is not for the faint of heart. It takes us on a journey all around the world, and spends most of its time in equatorial Africa and southeast Asia, tracing the paths of various diseases, some you have never heard of, others have been in the news for years. The diseases Quammen catalogs are in the running to be the Next Big One, and they all employ an ecological strategy that makes them ideal candidates.
The pathogens that cause diseases including influenza, SARS (or Sudden Acute Respiratory Syndrome), the very timely Ebola, Hendra, Herpes B, Rabies, Hanta, Nipah, and Marburg viruses, HIV/AIDS, Bubonic Plague, Lyme disease, Yellow Fever, Dengue Fever, in fact 60% of human infectious diseases are what is called “zoonotic”. A zoonotic pathogen, (or zoonosis) is one that resides in an animal reservoir, causing no harm to that animal species, but when circumstances are just right, can “spill over” into humans and cause disease in us (hence the name of the book). In the first example of the book, Quammen describes the outbreak of a little known (but very lethal) disease that affected humans and horses in Australia. It became known as Hendra virus, and after much field work, the reservoir was determined to be flying foxes, a type of bat, roosting in a tree in a horse paddock. The virus did not affect the bats at all, presumably it had coevolved with this particular species of bat over millions of years, but it turned out to be lethal to horses, exposed to the virus in bat urine and guano raining down from the tree in their paddock, and to the humans that were caring for the sick horses. The outbreak ended, but the virus is still there. A certain percentage of these flying foxes still carry this virus, which is why zoonotic diseases are virtually impossible to eradicate. We would have to kill literally every infected flying fox to eliminate this virus. That same story, of an animal host and a certain set of circumstances that allows for a spill over into humans is repeated for all of the zoonotic pathogens.
Those pathogens are mostly viruses by the way. Viruses are barely considered alive, because they can’t replicate themselves, they require the machinery of a host cell to do that for them. They have relatively short packets of genetic information, and when they hijack a cell’s DNA reproducing machinery, they are especially prone to error. Error sounds like a bad thing, and most of the time it is, mistakes in copying DNA usually lead to death, death of an individual viron. Occasionally though, an error leads to a new trait, one that affects the behavior of the viron, perhaps making it more hardy, more easily transmissible or able to infect a new species. That is evolution, and it is one of Quammen’s two main points about zoonotic disease. Ecology puts us in the path of these pathogens. As human behavior causes us to push further and further into wild habitats and deranges the order of natural ecosystems, we provide more and more opportunities for spill over. Its not that these pathogens seek us out, far from it, its just that there are so many of us, over 7 billion of us. We are getting harder to avoid. Ecology, our interactions with the world around us creates the opportunity, and evolution allows the pathogens to adapt to life in a human body.
This book is richly detailed and intensely researched. Quammen clearly spent years in the field in close proximity to spill over conditions to bring us this work. Its fascinating but if you are the type of person to lay awake at night worrying about things beyond your control, you may want to skip it. I for one, feel that knowledge can be empowering, so I read this book with gusto. In the end, when the Next Big One does emerge, and there is no doubt that it will, our actions as individuals actually do make a difference. We can make choices that these pathogens can’t, and these choices, along with the knowledge gathered by hundreds of brave scientists will help dampen the effect of whatever pandemic is coming next.
Spillover: Animal Infections and the Next Human Pandemic, David Quammen, 2012 W.W. Norton