Useful information for training your cephalopods

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Everyone knows the story of Konrad Lorenz and his goslings, right? It was a demonstration of imprinting: when young animals are exposed to a stimulus at a critical time, they can fix on it; Lorenz studied this phenomenon in geese, which if they saw him shortly after hatching, would treat him like their mother, following him around on his walks. Similarly, many animals seem to experience sexual imprinting, where they acquire the sexual preferences that will be expressed later on.

I just ran across a charming short letter about imprinting in cephalopods, and somehow the story seems so appropriate. Imprint a young, freshly hatched cuttlefish on something, and they don’t treat it like Mom, and they don’t later want to mate with it—they want to eat it. Lorenz was lucky he was working on birds rather than cephalopods.

The experiment is straightforward. Cuttlefish normally prefer to eat shrimp over crab. If, the day after hatching, small crab are put in the tank with the hatchlings for at least two hours, and then removed (the crabs are not eaten), then 3 days later when tested again, the cuttlefish will prefer to kill and eat crabs over shrimp. The procedure is very specific: they have to be exposed to crab for at least two hours, within 2 hours after sunrise on their first day after hatching.

The paper has a good, succinct description of why many animals would have this mechanism:

Precocial animals, like domestic
chicks and cuttlefish, which are
independent within hours of hatch
or birth and which receive no
posthatch parental care have
two options for acquisition of
information: bring it into the world
with you (unlearned preferences
for food, sexual partners and so on)
or pick up the information as you go
(trial and error learning). Imprinting
allows something in between:
a certain degree of flexibility in
response, useful for learning
information for which the timing is
likely to be predictable—food
seen in first few hours of life,
sibling/parents seen during
juvenile stages—but in which
specifying the exact details of
the experience is not useful.

An evil man could think of many nefarious things to do with this bit of information, I think.

Healy SD (2006)Imprinting: seeing food and eating it. Curr Biol.16(13):R501-502.

House jumps the shark

True confession: I try to watch the medical drama House when I can. It’s lead character is an acerbic and brilliant atheist M.D. (played by Hugh Laurie, a comedic actor—which was a smart casting decision), and the humor is snarky and dark. That’s just the kind of thing I enjoy. It’s been going downhill, I think, because the episodes have gotten far too predictable—there’s always a weird illness which is handled via increasingly wild semi-random diagnoses that always, and I definitely mean always, ends with the complete cure of the patient. The infallibility is wearing a little thin.

Last season’s finale almost made me give up. They turned the gross-out factor up to 11 (exploding testicles and eyeballs popping out), and resolved everything with the lamest, laziest television cliche: it was just a dream. I hoped it was just an aberration.

Last night’s episode, though, blew it. I have lost faith in House. <spoilers below>

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Developmental Biology 4181: Week 2

This week, my students are thinking about SIDS,
aging,
Christiane Nusslein-Volhard,
oncogenes,
hunger,
individuality,
worm movies,
obesity,
sunscreen, and whether to
divide or die. A fairly typical set of undergraduate concerns, right?

They’ve all also been reading chapters 3 and 4 of Carroll’s Endless Forms Most Beautiful, and their summaries are here: α,
β,
γ,
δ,
ε, and
ζ.

If you missed it, here’s Last week’s digest and a brief explanation of what it’s all about.

Patterning the nervous system with Bmp

I’m a little surprised at the convergence of interest in this news report of a conserved mechanism of organizing the nervous system—I’ve gotten a half-dozen requests to explain what it all means. Is there a rising consciousness about evo-devo issues? What’s caused the sudden focus on this one paper?

It doesn’t really matter, I suppose. It’s an interesting observation about how both arthropods and vertebrates seem to partition regions along the dorso-ventral axis of the nervous system using exactly the same set of molecules, a remarkable degree of similarity that supports the idea of a common origin. Gradients of a molecule called Bmp may be the primitive mechanism for establishing dorso-ventral polarity in animals.

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A new bathtime dilemma

Both Proper Study of Mankind and Thoughts in a Haystack have summaries of this bizarre paper that was published in Science last week, showing a connection between a sense of cleanliness and ethical thought. I guess it’s not surprising that physical sensations impinge on unconscious decisions, but it is interesting in that it hooks into some cultural rituals. I’m not at all clear on what it means, though: should I skip out on taking a shower so I’ll feel more compelled to do good in thought and deed to compensate, or should I do pre-emptive washing so I won’t be hindered from skullduggery?

How to make a tadpole

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I’ve been tinkering with a lovely software tool, the 3D Virtual Embryo, which you can down download from ANISEED (Ascidian Network of In Situ Expression and Embryological Data). Yes, you: it’s free, it runs under Java, and you can get the source and versions compiled for Windows, Linux, and Mac OS X. It contains a set of data on ascidian development—cell shapes, gene expression, proteins, etc., all rendered in 3 dimensions and color, and with the user able to interact with the data, spinning it around and highlighting and annotating. It’s beautiful!

Unfortunately, as I was experimenting with it, it locked up on me several times, so be prepared for some rough edges. I’m putting it on my list of optional labs for developmental biology—3-D visualization of morphological and molecular data is one of those tools that are going to be part of the future of embryology, after all—but it isn’t quite reliable enough for general student work. At least not in my hands, anyway. If one of my students were to work through the glitches and figure out how to avoid them, though, it could be a useful adjunct to instruction in chordate development.

If you want to play with it, I’ll give you a quick overview of what’s going on in the dataset. A paper by Munro et al. has used these kinds of data to summarize key events in the transformation of a spherical ball of cells into an elongate, swimming tadpole larva.

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Alien planets and cephalopodoids

The latest issue of Science has a fascinating article on Exotic Earths—it contains the results of simulations of planet formation in systems like those that have been observed with giant planets close to their stars. The nifty observation is that such simulations spawn lots of planets that are in a habitable zone and that are very water-rich.

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(click for larger image)
Final configuration of our four simulations, with the solar system shown for scale. Each simulation is plotted on a horizontal line, and the size of each body represents its relative physical size (except for the giant planets, shown in black). The eccentricity of each body is shown beneath it, represented by its radial excursion over an orbit. The color of each body corresponds to its water content, and the inner dark region to the relative size of its iron core. Orbital values are 1-million-year averages; solar system values are 3-million-year averages. Note that some giant planets underwent additional inward migration after the end of the forced migration, caused by an articial drag force. This caused many hot Earths to be numerically ejected, but had little effect outside the inner giant planet.

Dynamics of Cats has a better summary than I could give, and it leads in with this lovely illustration of an hypothetical alien organism on one of these hot water worlds.

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The only thing cooler than a cephalopod has to be a tentacled alien cephalopodoid. There’s a high-res version of that image at Dynamics of Cats—and I’ve got a new desktop picture.