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| Bear statue at the entrance of the Natural History Museum in Stockholm |
One example skull that I am going to show them during our tour is an hyena's skull because it is such a great example of the adaptations of the mouth of a mammalian predator for capturing and eating its prey.
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| British Museum of Natural History |
Any adaptations that help animals to eat their food are usually interesting to kids. Looking closely at the skulls and teeth of hyenas, alligators or wolves have particularly fascinating. (After all, they look like they might be able to eat us!) When we are making observations of skulls and teeth we sometimes talk about how the teeth on a mammal are like a tool kit. Humans can use their hands and tools such as knives and forks to get their food. But, to be able to survive animals have to be capture and then break up their food into reasonable bite sizes. Predator's teeth are often important for both catching prey and then also to able to get through the hard outer coating to get to the good stuff inside.
There is a completely different group of animals also has a specialized tool kit for getting their food but their tools are all modified appendages. This means that instead of lots of teeth (which they don't have) they have lots of legs. I am thinking of the crustaceans who are called decapods because they have 10 legs. Of the five pairs fo legs there are many possible functions from walking to digging to climbing but the front pair of legs are usually modified into large claws. Among the crabs, shrimp, crayfish and lobsters there is a wild array of modifications to the front claws which have all kinds of advantages for defense, signally to other crabs as well as capturing or stunning and holding food. Or even to stay cool!
Male fiddler crabs use their giant claws to keep cool as well as attract females, say scientists. Click here to read the BBC Nature article by Ella Davies
All this discussion of adaptations of crustaceans is really just my excuse for featuring the lastest blog post from Robert Krulwich of RadioLab fame. Earlier this year RadioLab (one of my favorite podcasts) aired an entire episode on color (Link to Episode on Color here). Which brings me back to the topic of crustaceans because there is yet another amazing adaptation of these crazy looking creatures. It seems that one group of crustaceans, called mantis shrimp- can see a much wider array of the light spectrum than we can. Whereas we have three different color cones in our eyes mantis shrimp have 16 different kinds of color receptors in their eyes.
To give us a small sense of how much more information there might be in being able to see such a wide range of colors the RadioLab team enlisted a choir to sing the range of frequencies that we can hear as a kind of auditory translation of the rainbow. And then, since we humans are such visual creatures the RadioLab crew were nice enough to also post a video about working with the choir in making this episode- and check out near the end their version of Handel's Messiah - rewritten to fit for the Mantis Shrimp. -Hallelujah Mantis Shrimp
And THEN - this great RadioLab program on color and the many colors a mantis shrimp can see inspired a artist/cartoonist/storyteller named Matthew Inman to create "an ode to an animal that he freely admits isn't charming, isn't nice, isn't gentle, isn't even good — which is why it melts his heart."
Part 2) If you haven't already gone directly to the cartoon from the Oatmeal mentioned in Krulwich Wonders post - then click on the link below and you will then want to share it with all the Gr 3-4 students that you know....I think this might have been written with 8-10 year olds in mind.....Here is the link to the cartoon that you must read-
But there is MORE!
Let me direct you now to a research team at the UC Berkeley Museum of Paleontology run by
Roy Caldwell . His group has been studying stomatopods for over 30 years. (Stomatopods is the scientific word for mantis shrimp). Here is the link to their research-
This group found some more interesting information about their vision. Here is a short list of some of their findings:Stomatopod eyes are unusual for several reasons:
- they have stereo vision with just one eye;
- each eye is up on a stalk, with a wide range of motion;
- stomatopods have up to 16 visual pigments (in contrast, we humans have three—red, blue, and yellow);
- stomatopods can also see ultra-violet and infra-red light, and some can even see polarized light
The eyes of a mantis shrimp
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| The eyes of a mantis shrimp |
Can you believe that? They not only see many more colors than we do - some of them have polarizing filters on their eyes!
"Researchers….have just recently demonstrated that they had polarizing filters in their eyes……The images in the animation above were taken using a polarizing filter—we wouldn’t see the flashing red and white signals with only the naked eye. Based on his observations, Dr. Caldwell thinks that these stomatopods may use patterns visible only with polarized filters for communication."
Click here to watch the short video that illustrates how the mantis shrimp can signal each other. But, only an animal with polarizing lens would be able to see these signals. So, it would be like have a secret code that none of the other members of underwater ecosystem would be able to see.
In most stomatopod groups, after mating with a male, the female stomatopod lays eggs in her burrow. However, in one group ofspearers, the males and females are monogamous (meaning they stay together and share a burrow)…..The male and female live in the same burrow, but have different “jobs”—the female takes care of the eggs and the male hunts for food for both of them! Note that the male in the image at right has much larger eyes and raptorial appendages."
So clearly both the excellent eyesight and the large front claws are related adaptations for hunting for food. Which makes one wonder - which came first - the amazing eyesight or the killer front claws?
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Example of a modern mantis shrimp, Odontodactylus scyallarus. It is well known for using heavily calcified clubs as weapons. Natural History Museum.
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The Museum of Natural History has a short posting on its website that says "the description of new material means that our understanding of the evolution of proto-mantis shrimp is in flux. Several fossil localities from the Carboniferous in Europe and North America have yielded particularly important material that has shaped our understanding of the diversity of the group….
One of the most interesting topics the fossils shed light on is the evolution of the pair of specialised ballistic claws that modern mantis shrimp use to catch their prey. It turns out that this specialisation had already developed in some archaeostomatopods of the Carboniferous."
Which is using a lot of long words to say - we have found some very interesting fossils that date back 300 million years and they show that those raptorial front claws were already developed by then. So, there were mantis shrimp clubbing their prey even back in the Carboniferous seas. But, that says nothing about the amazing eyes. What it does tell us is that this adaptation has stood the test of evolutionary time. They work well!
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Someday I will write a whole post on this blog dedicated to hyenas but for now I have to leave to it here - so here are a few Hyena links that might be of interest -
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