Male kangaroos kick at each other. Male elephant seals gore each other with their large canine teeth. Male Giant Australian cuttlefish also undergo intense competition for females, but besides physically grabbing and biting each other, they also showcase a brilliant pattern on their skin.
Dr. Roger Hanlon who studies cephalopod camouflage at the Marine Biological Laboratory in Woods Hole, MA describes the mesmerizing “passing cloud” pattern and the purpose behind this agonistic display.
Animation and Audio Editing by Natividad Chen and Kimberly Ulmer. This podcast is released under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 license.
Here is a little plant that starts it’s life high up in the tree tops, where it can find more light than the dark understory of the rainforest. As it grows though, soon getting enough water becomes limiting factor, and the plant will drop a shoot to the ground.
Matt Ogburn, a graduate student in Erika Edwards’ lab at Brown University, describes this little plant, the strangler fig, and explains how it eventually grows to take over the whole host tree and strangle it to death.
This is a really nice video that was published in the Journal of Plankton Research this past February, as a part of this article about krill.
Even though krill make up a large fraction of the living mass of the ocean (and are also the food for large charismatic sea mammals), many aspects of their biology is unknown, including the way they reproduce. Recently Dr. Kawaguchi and his colleagues filmed the process happening near the sea floor, which was surprising because krill are notorious for living their lives swimming around up higher in the water, far from the floor.
The footage that the researchers collected was a bit chaotic (above, left), and so they gave it to Lisa Roberts, an animator (and CreatureCast contributor), to illustrate the process. She traced the motions of the crustaceans from the videos, and also practiced the moves with some shrimp from the market (above, right).
The original video footage from the deep sea is also really nice to watch, and can be found here, at the Journal of Plankton Research website.
This video is about the enzymes that, for me, first turned cells into little toy chests full of delightful tiny gadgets.
All of the mechanical things that our bodies do, like keeping other things out, or seeing, can be described by somewhat abstract functions. For example, ‘the skin makes a protective sheet’ or ‘the lens focuses light’. But then all of those abstract functions can be broken down again into mechanical motions of the small molecules inside the cells, complete with hinges and springs, making them seem tangible once more, at least to my mechanism-oriented mind: The outside of each skin cell is littered with little molecules that hold on to the same types of molecules on the next cell in a strong handshake, forming a tight, grime-proof layer, while lens cells pack hundreds of copies of a single type of protein up tight against each other, forming almost a crystal, and then jettison all of things in the cell that would scatter light, like DNA or mitochondria, in order to let light pass cleanly through the cell.
This story in this video is about a problem that all living things have — how long and thin DNA is, and how easy it would be to get it all tangled. Not only is there a huge amount of DNA in each cell (around two meters in each human nucleus, for example), but also every time a cell divides into two, the two strands of all of that DNA have to be untwisted from each other to be copied. Think about pulling the fibers of a length of twine apart; the wound end gets tighter and tighter and then twists up on itself, making it impossible to move forward. Thankfully there are these little enzymes, called topoisomerases, that are there to iron out the wrinkles.
In the vast ocean, without walls and far from the floor, jellyfish can become drifting islands of activity. Creatures from far and wide will congregate on them to act out the ups and downs of life and death. Jellyfish have symbiotic relationships with living things of all sizes, from fish and shrimp that feed off them or off the pieces of food left between their tentacles, to single-celled photosynthesizing organisms that take shelter inside the cytoplasm of the jellyfish’s cells.
In this video, Trisha Towanda talks about one particular jellyfish, the fried egg jelly, and some of the other creatures that hang around it. There are moon jellies that the fried egg jelly eats. These moon jellies have little parasitic crustaceans on them called amphipods, which jump to the fried egg jelly while the moon jelly is being eaten. There are also crabs that ride around on the fried egg jelly, that are parasitic in their youth, but then grow to be helpful symbionts by eating off the little amphipods. This sort of coming of age story, where a symbiont’s relationship changes over its lifespan is an unusual one. Trisha put the pieces together by staring at them for hours and days and weeks when she was in Erik Thuessen‘s lab at Evergreen State College.
Many thanks to Trisha Towanda, who is now stationed in the Seibel lab at the University of Rhode Island. This video was edited and animated by Sophia Tintori, with an original score by local pop hero Amil Byleckie. It is released under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 license. Here is the paper Trisha wrote about the story.
Early last year, at the Australian Antarctic Division (AAD), I saw an unusual sight: the birth of a live Antarctic krill, Euphausia superba.
The newborn appeared on a video screen that projected the view of a camera poised over a petri dish. A tremulous form emerged from its egg with its legs beating furiously!
This event began a continuing conversation with krill research leader, So Kawaguchi.
Back in my Sydney studio, I worked with So’s words and images. He explained (by email) how krill grow, and sent me diagrams by John Kirkwood to work with. I also found data sets online of how krill appendages move (Uwe Kils). Piano music was improvised by an 11 year old friend, Sophie Green.
This is the first of some animations that I am making to more fully describe this elusive and most important creature.
Krill are central to the marine life food web. Their health is endangered as a result of oceans becoming more acidic (as carbon increasingly enters the atmosphere and then dissolves into the water).
A new research project at the AAD is to record changes in normal krill development in increasingly acid water. Next month (June 2010) I return to the AAD krill nursery to find out more about this research.
I will also record So Kawaguchi describe what he has identified as a circling krill mating dance. What a fine gesture of continuity!
Last month we posted a video of a siphonophore (one of the Dunn lab’s favorite animals) swimming freely in the ocean. In this next installment of CreatureCast, Casey Dunn describes how siphonophores help us question what we think of as an individual.
There are different ways to think of individuality. Individuality can refer to function- whether an organism operates and interacts with the world as a unit. A fish is a functional individual, but so is an ant colony. Individuality can refer to evolutionary descent. In this respect our liver is not an individual, there was no ancestral free-living livers out there that our liver is descended from. But our mitochondria are individuals in this sense. They evolved from free-living bacteria that became incorporated into other cells. Individuality can also refer to the process of evolution. In this sense an individual is any entity that has the properties necessary for evolution by natural selection- it reproduces and has variable heritable properties that influence the chances of survival. This could be a free living cell, a cell in a body, an entire multicellular organism, and even groups of organisms in some cases.
All of these definitions of individuality are in alignment in most of the organisms we are familiar with. A bird, a rose bush, and a fly are all individuals as functional entities, according to their ancestry, and as units of selection. This makes it easy to get lulled into thinking of individuality as a monolithic property.
A siphonophore colony is a functional individual. But a siphonophore colony is made up of many parts that are each equivalent to free living organisms such as sea anemones and “true” jellyfish. So by the evolutionary descent definition it is a collection of individuals. The colony as a whole is acted upon by natural selection, making it an individual in the sense of the process of evolution. But it is entirely unclear whether natural selection can act on the parts within the colony, as it does on our own cells when we get cancer, since we don’t know about the heritability between the parts of the colony.
Siphonophores, by forcing us to disentangle what we mean when we call something an individual, help us understand the evolutionary origins of individuality. These different aspects of individuality don’t necessarily evolve at the same time, and one or more of them can even be lost. Organisms like siphonophores provide glimpses of these different combinations of individuality.
Most of the stills are plates from the first papers describing siphonophores. They were published from the mid 1800′s to the early 1900′s by Henry Bryant Bigelow, Ernst Haeckel, and Karl Vogt.
Here in the Dunn lab, siphonophores are our favorite animal and the focus of much of our research.
Dr. Phil Pugh is a good friend of the lab, and he also happens to have described more new species of siphonophores than anyone who has ever lived. In the video below, he describes what it’s like to come across a siphonophore in the deep sea with a submarine. What looks like one long body in this video is actually a free-swimming colony of clones — many genetically identical bodies that are all attached. But each body in the group isn’t just like its neighbor. They each do a specific job for the colony. Some individuals will swim, some will catch food, and some will reproduce.
More on siphonophore biology can be found in papers here and here. But we’ll talk about all that later — for now, just take a look.
A couple of weeks ago the Dunn lab went out after work, and we got to talking. There’s this thing that usually happens whenever we get together after a day in the lab or field– being a group where everyone focuses in one way or another on the diversity and evolution of reproduction and development, we start to tell stories about how animals reproduce. Someone mentions some surprising tidbit of reproductive biology they recently heard, and that sets it off. Then someone else remembers a weirder story, and tells it. This spurs someone else’s memory, and so on, and then I start feeling overwhelmed.
Well, this time we got caught up on the issue of female choosiness. It takes more energy and resources to make an egg packed with resources, or to raise offspring, or to carry a baby inside the womb, than it does to make sperm. This often leads females to be more selective about their mates than males are. We started talking about ways in which female choosiness manifests itself; sometimes through behavior, sometime through anatomy, and sometimes at the level of the cell. And then sometimes it is all for naught.
In this episode of CreatureCast Rebecca Helm, a graduate student in the Dunn Lab, recounts a few short stories about the many levels of reproductive selection.
