Carnivalia, and an open thread

We just had one of these!

Well, just to flesh it out a little more with some random links, here are some photos. I was told the second one made someone think of me (warning: body modification!). And, jebus help me, for some reason I thought this photo was very sexy. Or appetizing. I don’t know, something in the midbrain flickered.

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Oh, and several of us sciencebloggers were interviewed for an article by Eva Amsen on “Who benefits from science blogging?” It doesn’t mention the benefit of people sending you pictures that tickle the cingulate.

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.

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.

Friday Cephalopod: Septopus!

Go ahead, count ’em. Since there were some comments about octopuses with an odd number of arms, here’s an example. Males of this species have a highly modified arm (the one they use for sex) that is tucked away in a pouch, so they have the appearance of a seven-armed octopus.

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Haliphron antlanticus, the seven-arm octopus

Figure from Cephalopods: A World Guide (amzn/b&n/abe/pwll), by Mark Norman.

What? No cephalopod genome project?

I was reading a review paper that was frustrating because I wanted to know more—it’s on the evolution of complex brains, and briefly summarizes some of the current confusion about what, exactly, is involved in building a brain with complex problem solving ability. It’s not as simple as “size matters”—we have to jigger the formulae a fair bit to take into account brain:body size ratios, for instance, to get humans to come out on top, and maybe bulk is an inaccurate proxy for more significant matters, such as the number of synapses and nerve conduction velocities.

There’s also a growing amount of literature that takes genomic approaches, searching for sequences that show the signatures of selection, and plucking those out for analysis. There have been some provocative results from that kind of work, finding some candidate genes like ASPM, but another of the lessons of that kind of work seems to be that evolution has been working harder on our testis-specific genes than on our brains.

The encouraging part of the paper is that the authors advocate expanding our search for the correlates of intelligence with another group of organisms with a reputation for big brains, but brains that have evolved independently of vertebrates’. You know what I’m talking about: cephalopods!

The Cephalopoda are an ancient group of mollusks originating in the late Cambrian. Ancestors of modern coleoid cephalopods (octopus and squid) diverged from the externally-shelled nautiloids in the Ordovician, with approximately 600 million years of separate evolution between the cephalopod and the vertebrate lineages. The evolution of modern coleoids has been strongly influenced by competition and predatory pressures from fish, to a degree that the behavior of squid and octopus are more akin to that of fast-moving aquatic vertebrates than to other mollusks. Squid and octopuses are agile and active animals with sophisticated sensory and motor capabilities. Their central nervous systems are much larger than those of other mollusks, with the main ganglia fused into a brain that surrounds the esophagus with additional lateral optic lobes. The number of neurons in an adult cephalopod brain can reach 200 million, approximately four orders of magnitude higher than the 20-30,000 neurons found in model mollusks such as Aplysia or Lymnaea. Cephalopods exhibit sophisticated behaviors a number of studies have presented evidence for diverse modes of learning and memory in Octopus and cuttlefish models. This learning capacity is reflected in a sophisticated circuitry of neural networks in the cephalopod nervous system. Moreover, electrophysiological studies have revealed vertebrate-like properties in the cephalopod brain, such as compound field potentials and long-term potentiation. Thus cephalopods exhibit all the attributes of complex nervous systems on the anatomical, cellular, functional and behavioral levels.

Unfortunately, the purpose of the paper is to highlight an unfortunate deficiency in our modern research program: there is no cephalopod genome project. The closest thing to it is an effort to sequence the genome of another mollusc, Aplysia, which is a very good thing—Aplysia is a famous and indispensable subject of much research in learning and memory—but it’s no squid. The authors are advocating additional work on another animal, one with a more elaborate brain.

A parallel effort on a well-studied octopus or squid should provide insights on the evolutionary processes that allowed development of the sophisticated cephalopod nervous system. For example, have cephalopods undergone accelerated evolution in specific nervous system genes, as has been suggested for primates? Have specific gene families undergone expansion in the cephalopod lineage and are these expressed in the nervous system? Are there clear parallels in accelerated evolution, gene family expansion, and other evolutionary processes between cephalopods and vertebrates? Answers to these and related questions will provide useful perspectives for evaluation of the processes thought to be involved in the evolution of the vertebrate brain.

I’m all for it—let’s see a Euprymna genome project!

Jaaro H, Fainzilber M (2006) Building complex brains—missing pieces in an evolutionary puzzle. Brain Behav Evol 68(3):191-195.