Gooseneck barnacles and Barnacle Geese

One of the joys of biology lies in appreciating how strange and varied the world is. When humanity starts to feel claustrophobic, you can imagine the life of an albatross, aloft over the ocean for most of her life, searching out schools of delicious fish by their scent; or a cuttlefish, flashing colored signals at his companions as he shoots through the currents, flexible tentacles waving. When the world feels narrow and limiting, you can remember that clownfish change sexes depending on their place in the dominance hierarchy, with males becoming female when they advance to the position of top dog.

Yet—amazingly—biology used to be even wilder. Before satellite tracking and genetic analysis, before “biology” was a recognized science at all, natural philosophers looked at a perplexing natural world and invented some truly outside-the-box explanations for what they saw.

Some of these are fairly well known: for example, the idea that there is a “homunculus”—a tiny human—inside the head of each human sperm cell.

preformation

As drawn by N. Hartsoeker in 1695. Public Domain, https://commons.wikimedia.org/w/index.php?curid=635170

To be fair, we now know that sperm (and eggs, etc.) contain the genetic blueprint for building a human, which isn’t all that far off from containing a tiny human.

But my favorite old science myth involves—of course!—birds.

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Animal accomplishments that have caused my students to break into applause

I’m teaching an Animal Behavior course this semester. The lectures are 80 minutes long and exactly during the sleepiest time of the afternoon; I enjoy the challenge of getting a reaction from the students under these circumstances. Videos of baby animals in peril always get attention (some good ones: marine iguana, barnacle goose, water buffalo), but they’re so reliable it almost feels like cheating.

My students have actually broken into applause during lecture three times so far. One of these will not be discussed in detail (it involved the recitation of poetry), but the other two were in response to two quite different animal accomplishments, which I thought I would share.

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Hidden worlds: whale falls

I like to read science fiction. I particularly enjoy a good alien world, like Neal Asher’s world of hyper-aggressive invertebrates or Lois Bujold’s planet of radially symmetric beasts. Still better than these, however, are the alien worlds right here on Earth, hidden in plain sight. (Well… if “on the same planet” counts as “in plain sight.”) The hidden world I’d like to talk about today is that of whale falls.

A “whale fall” is just a nice way of saying a dead whale: when a whale dies in the ocean, it sinks—falls—to the bottom, and you have a whale fall. Whale falls are different from other dead animals in two big ways. First, they are, well, big. No other living animal gets as big as our biggest whales. When one of those dies, that’s a lot of dead whale.

Also, whale falls are pretty cool in their pre-fall form.

Also, whale falls are pretty cool in their pre-fall form.

Second, when they fall to the ocean floor, they change the environment on the ocean floor dramatically. A dead animal in a forest or jungle or lake is a piece of dead meat in a habitat already full of other kinds of food: leaves, berries, insects, fish, etc. Some animals in these habitats will scavenge on the dead meat, but many other animals will ignore it. The deep ocean floor is not like a jungle. It is barren, with no sunlight to support plants or plankton, which are generally the food sources that the rest of a food chain depends on. The only organic food sources near the deep sea floor are the dead things that fall down from the water column above, picturesquely named “marine snow;” and that water column is filled with creatures trying to eat anything they can find, so not a lot makes it all the way to the bottom. When a dead whale lands on the ocean floor, it is the equivalent of an enormous banquet being dropped into the middle of a desert.

When a whale falls, it gives rise to an entire ecosystem by itself.

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Is that a friendly (woolly, stingy) face I see?

Humans see faces everywhere. We see a face in the craters of the moon, in wall sockets, sideways in punctuation :-) and just about anywhere else two dots and a line are arranged in even approximately the same positions as two eyes and a mouth.

Don't those drawings of outlets look like faces?

Don’t those drawings of outlets look like faces?

Once we recognize something as a face, we process it differently from other visual stimuli. Certain parts of the brains are triggered preferentially by faces. We are especially good at perceiving faces: we can pick out matching faces faster than matching abstract patterns, and distinguish non-matching faces more easily than other images. This only works, however, when our brains recognize the faces as faces: if you flip faces upside-down, they no longer trigger the “face” switch for us, and we become much worse at distinguishing them. The same thing happens if you digitally scramble facial features, so that there’s an ear in the middle and an eye on the chin and a mouth slanting across the forehead, or any other mix-up that makes the face no longer be arranged like a face. Our brains are specialized to perceive face-shaped patterns much better than other patterns.

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Nudibranchs defend themselves with their food

Nudibranchs, or sea slugs, are descended from animals with protective shells like those of modern snails. Nudibranchs have lost that shell, leaving them potentially vulnerable: squishy morsels in an ocean full of hungry things. But nudibranchs have some tricks to avoid becoming someone else’s meal: they use their own food to protect themselves.

Hermissenda crassicornis may not have a shell, but he is well-defended. Photo by M. LaBarbera

Hermissenda crassicornis may not have a shell, but he is well-defended.
Photo by M. LaBarbera

One trick is to steal the defenses of your prey. Many nudibranchs eat stinging animals like hydroids and anemones. These animals use specialized stinging cells to catch their own prey and to defend themselves.

Hydroids. The stinging cells are on the ends of the long tentacles, waiting to catch prey. Photo by M. LaBarbera

Hydroids. The stinging cells are on the ends of the long tentacles, waiting to catch prey.
Photo by M. LaBarbera

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