My dad gave me homework. He asked me to tell him all about snakeheads (Family Channidae) when I came down on Friday for a visit. So I did what any good daughter would do and I did a search on the greater snakehead fish (Channa micropeltes) and the northern snakehead fish (Channa argus). Turns out they are kinda cool, speaking from an ecological perspective.
They are part of a family of freshwater fish native to Asia, from China to India and down into the islands of Indonesia. There are also species native to Africa, but I don’t think those are the ones my dad heard about, as the hubbub here in the US is that they are invasive species.
Anatomically, the fish are unremarkable, with a long dorsal fin running most of the length of it’s back, and fan-shaped tail fins. Their heads are kind of flattened, I suppose like a snake head, and the mottled blotchy brown coloration reminds me of patterns on snakes bodies, like pythons or boa constrictors.
They grow quickly and can get quite large, as evidenced by this video courtesy of National Geographic.
Snakeheads were brought to America for food and as aquarium fish. However, as people are wont to do they release them in nearby ponds, rivers or streams when they get too large or they no longer need them, and the snakeheads settle and begin making more snakeheads.
They caused a stir in 2002 in Maryland, where an angler caught one in a pond. He took it to a local wildlife and fisheries office for identification. The authorities visited the pond and subsequently caught some hatchlings, indicating the population was well-established. This wouldn’t be such a problem, but the snakeheads are sneaky.
They are one of the few species of fish that need to breathe air. Yes, I said breathe, meaning they don’t use just their gills; they also have what is called a “suprabranchial organ”, which is a kind of a branch of their vascular system allowing them to oxygenate their blood via inhalation of atmospheric oxygen.
While snakeheads don’t actually walk, they do have a decidedly un-fishlike ability to scoot or flop themselves from one body of water to another. Thus, the concern of wildlife and fisheries agents.
There is plenty more I could say about invasive species but I think I should wait, or this will become a longwinded entry.
So, there you have it Dad, everything you wanted to know about snakeheads.
Sunday, December 13, 2009
Tuesday, November 17, 2009
Warm Blooded Dinos?
I am not a paleontologist, but I am a big fan of scientific controversy. I love it when two sides argue about how flight originated or how new fossils may be related to our own hominid lineage. That’s why the recent findings that large bi-pedal dinosaurs like the beloved Tyrannosaurus rex may not have the typical large lizards we have long thought really caught my attention.
It’s generally consensus these days that some dinosaurs were birds rather than lizards, and the lineage has been split to include non-avian and avian branches. But there is still controversy among experts as to whether or not these dinos were warm-blooded like their birdy brethren or cold-blooded like their lizardy links. A new study published in the online scientific journal PLoS ONE on Nov. 11th brings to light some new information.
Say the study authors, endothermy, or warm-bloodedness, was widespread “in at least larger non-avian dinosaurs.” The results of their study seem to indicate that the ability to maintain a constant internal temperature may have originated earlier than previously believed.
What this essentially means is that once again we are rethinking how these extinct giants behaved. For the longest time, large dinosaurs like the T-rex were considered unwieldy, hulking and awkward. Now there’s evidence that there was more power and precision behind their lumbering movements.
So why is this such a point of contention? Because being warm-blooded and cold-blooded are very different and require different energy expenditures, different rates of respiration, and different natural histories altogether.
Cold-blooded animals (termed ectothermic), such as amphibians, reptiles and the ilk, rely on the environment to maintain body heat. They generally adapt behaviors to soak up as much heat and sun as possible to run their metabolic processes.
Warm-blooded animals are everything else—including birds (or avian dinosaurs). We can maintain homeostasis (i.e., regulate and maintain a constant body temperature through metabolism). But doing this requires much more energy consumption and output, and requires different anatomical and physical traits. It also means we can live anywhere, hunt for food anytime, and not have to worry about the environment to meet our temperature regulation needs.
So the fact that there is evidence for endothermy among dinosaurs has huge ramifications. We may need to reconsider how we classify them, and even how they became extinct.
Reptiles, a lineage of animals dating back over 300 million years, include organisms such as the extinct dinosaurs and the extant (still living) species of lizards, crocodilians, turtles. It was later expanded to include birds, based on genetic and molecular evidence. These new findings could also lead to more accurate phylogenies, or evolutionary trees.
It’s generally consensus these days that some dinosaurs were birds rather than lizards, and the lineage has been split to include non-avian and avian branches. But there is still controversy among experts as to whether or not these dinos were warm-blooded like their birdy brethren or cold-blooded like their lizardy links. A new study published in the online scientific journal PLoS ONE on Nov. 11th brings to light some new information.
Say the study authors, endothermy, or warm-bloodedness, was widespread “in at least larger non-avian dinosaurs.” The results of their study seem to indicate that the ability to maintain a constant internal temperature may have originated earlier than previously believed.
What this essentially means is that once again we are rethinking how these extinct giants behaved. For the longest time, large dinosaurs like the T-rex were considered unwieldy, hulking and awkward. Now there’s evidence that there was more power and precision behind their lumbering movements.
So why is this such a point of contention? Because being warm-blooded and cold-blooded are very different and require different energy expenditures, different rates of respiration, and different natural histories altogether.
Cold-blooded animals (termed ectothermic), such as amphibians, reptiles and the ilk, rely on the environment to maintain body heat. They generally adapt behaviors to soak up as much heat and sun as possible to run their metabolic processes.
Warm-blooded animals are everything else—including birds (or avian dinosaurs). We can maintain homeostasis (i.e., regulate and maintain a constant body temperature through metabolism). But doing this requires much more energy consumption and output, and requires different anatomical and physical traits. It also means we can live anywhere, hunt for food anytime, and not have to worry about the environment to meet our temperature regulation needs.
So the fact that there is evidence for endothermy among dinosaurs has huge ramifications. We may need to reconsider how we classify them, and even how they became extinct.
Reptiles, a lineage of animals dating back over 300 million years, include organisms such as the extinct dinosaurs and the extant (still living) species of lizards, crocodilians, turtles. It was later expanded to include birds, based on genetic and molecular evidence. These new findings could also lead to more accurate phylogenies, or evolutionary trees.
Sunday, November 15, 2009
Your DNA damage looks great, did you get just get back from the beach?
My students in Biology 101 are learning about DNA right now and one asked me how UV radiation causes damage to our genetic material. I know the basics, but was unfamiliar with the process. So I, of course, was intrigued, and had to look it up. Bear with me, I’ve tried to make this as simple and bare-bones as possible, so don’t let your eyes glaze over (like those of some of my students) when you see big scientific words.
DNA structure consists of a backbone molecule made up of sugar (a deoxyribose sugar, what the D in it’s name stands for) paired with phosphate molecules. Attached to each of those sugars is a nitrogenous base: adenine (A), thymine (T), guanine (G) or cytosine (C). It’s the complimentary pairing nature of these bases that allows for such perfect replication of our genetic material; A pairs with T, and G pairs with C, and that is what gives DNA it’s structure, chemical properties, and it’s ability to replicate so faithfully.
DNA replicates, or copies itself, in a process that is nothing short of amazing. The double-helix structure unwinds (with the help of an enzyme) and each parent strand is faithfully copied via complimentary base pairing. Throughout the process are “checkpoints” to prevent errors and proofreaders that won’t allow the DNA to code for protein unless things are correct.
Most DNA damage interferes with the ability to proofread or prevent incorrect proteins from being made, which is the case with UV radiation. UVB light causes one of the nitrogenous bases, thymine, to pair with itself instead of with adenine. These thymine base pairs next to each other in genetic sequences bond together into thymine dimers, an incorrect sequence which disrupts replication in the strand and which enzymes cannot read or copy. This leads to the production of melanin--a tan, or in severe cases, sunburn. Sunburn is the body’s way to get rid of cells damaged by UV radiation.
Direct DNA damage is reduced by sunscreen, which prevents sunburn; it won’t necessarily keep you from getting a tan. On the skin’s surface, sunscreen filters the UV-rays, decreasing their intensity. When sunscreen molecules penetrate the skin, they protect against direct DNA damage because the UV-light is then absorbed by the sunscreen and not by DNA.
So, that beautiful golden color you get when you lay out in the sun, the one you think makes you look so good? Yeah, not so good. That damage accumulates in your DNA, and over time can lead to skin cancer.
We do need some sun, so I’m not advocating staying inside on beautiful afternoons, just be careful and use sunscreen to decrease your risks of skin cancer.
DNA structure consists of a backbone molecule made up of sugar (a deoxyribose sugar, what the D in it’s name stands for) paired with phosphate molecules. Attached to each of those sugars is a nitrogenous base: adenine (A), thymine (T), guanine (G) or cytosine (C). It’s the complimentary pairing nature of these bases that allows for such perfect replication of our genetic material; A pairs with T, and G pairs with C, and that is what gives DNA it’s structure, chemical properties, and it’s ability to replicate so faithfully.
DNA replicates, or copies itself, in a process that is nothing short of amazing. The double-helix structure unwinds (with the help of an enzyme) and each parent strand is faithfully copied via complimentary base pairing. Throughout the process are “checkpoints” to prevent errors and proofreaders that won’t allow the DNA to code for protein unless things are correct.
Most DNA damage interferes with the ability to proofread or prevent incorrect proteins from being made, which is the case with UV radiation. UVB light causes one of the nitrogenous bases, thymine, to pair with itself instead of with adenine. These thymine base pairs next to each other in genetic sequences bond together into thymine dimers, an incorrect sequence which disrupts replication in the strand and which enzymes cannot read or copy. This leads to the production of melanin--a tan, or in severe cases, sunburn. Sunburn is the body’s way to get rid of cells damaged by UV radiation.
Direct DNA damage is reduced by sunscreen, which prevents sunburn; it won’t necessarily keep you from getting a tan. On the skin’s surface, sunscreen filters the UV-rays, decreasing their intensity. When sunscreen molecules penetrate the skin, they protect against direct DNA damage because the UV-light is then absorbed by the sunscreen and not by DNA.
So, that beautiful golden color you get when you lay out in the sun, the one you think makes you look so good? Yeah, not so good. That damage accumulates in your DNA, and over time can lead to skin cancer.
We do need some sun, so I’m not advocating staying inside on beautiful afternoons, just be careful and use sunscreen to decrease your risks of skin cancer.
Monday, March 9, 2009
Fueling my new obsession with mitochondira
I'm currently reading a fabulous book that I found just laying all by it's lonesome (i.e., in the wrong place) in Barne's and Noble a couple of weeks ago. It's entitled Power, Sex, and Suicide (now do you see why I had to have it?). And, if a fabulous title isn't enough it's about my newest favorite organelle--the mitochondria.
Dr. Nick Lane, a British science writer, does a very admirable job with this subject, especially in light of all the research being done in this area. Unfortunately, I am not very far along in the book, but it's one of those I can't put down so far. It's interesting and inspiring (as a wanna be science writer), as Lane says things like "the living cell is a minute universe" (p. 8) and he calls mitochondria the "clandestine rulers of the world" (introduction). I love these descriptions!
As I get further in to it, I will share more, but I wanted to share the title and the fact that it's a good read, at least thus far.
Dr. Nick Lane, a British science writer, does a very admirable job with this subject, especially in light of all the research being done in this area. Unfortunately, I am not very far along in the book, but it's one of those I can't put down so far. It's interesting and inspiring (as a wanna be science writer), as Lane says things like "the living cell is a minute universe" (p. 8) and he calls mitochondria the "clandestine rulers of the world" (introduction). I love these descriptions!
As I get further in to it, I will share more, but I wanted to share the title and the fact that it's a good read, at least thus far.
Monday, February 23, 2009
Thesis writing
So the time is coming up fast for me to have a thesis written for my master's degree. Bah. I'm not so sure I can do this. Oh, yeah, a year or two ago I was all gung ho and "I'm gonna be a science writer" and now that it's time to begin actually writing, and querying and publishing, I'm chickening out.
I have my classes under my belt, and though it was not a traditional education, I feel quite well educated through the ILPS program at Antioch McGregor. (Don't get me started on them, I will digress quite a while and wax poetic about their virtues.) I'm scared, though, because not only do I need to live up to their standards, I have to live up to mine.
I feel a little like Charlie Brown just as he gets ready to run toward Lucy holding the football.
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