Trilobites are not isopods

Prof. PZ Myers at Pharyngula attended a talk by Kent Hovind at a U.S. college, Cloud State University. Among other things, Dr. Myers had this to say:

And the lies were just so painfully blatant: as an example, he claimed that trilobites weren’t old and they weren’t extinct, and to ‘prove’ his claim, he showed a picture of an arctic isopod and announced that there it was, alive and crawling, proof that the biology professors have all been lying to you.

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My comments:
Young-earth creationist Kent Hovind includes in his talks an assertion that trilobites are still around because he has—ta-da!—a picture of an isopod. That’s like saying that horseshoe crabs live in the Prairies because you found a grasshopper. But “Dr.” Hovind seems unaware of his mistake. It’s almost as if Hovind’s attitude towards God’s creations is, “If you’ve seen one bug, you’ve seen them all.” Is it a lie if you don’t care?Isopods are only distantly related to trilobites. Allow me to introduce Hovind to the Tree of life page for arthropods.

The further apart the names are in the list, the more distantly related they are. Trilobites are distinguished by the three lengthwise sections of the body. (Harvard University shows a nice selection of trilobite species.) They are also extinct, as shown by the little dagger beside their name. I know of no living crustaceans with bodies divided into three lengthwise lobes. Here is a fossil of a trilobite:
Here is an isopod:

You’ve seen them, because sowbugs and pillbugs are isopods. Sowbugs and pillbugs are those little, segmented grey bugs that hide in damp places. Pillbugs curl into a ball when you pick them up; sowbugs just run away. I remember learning in school that they are crustaceans and breathe with gills, so they must live around moisture.

Both trilobites and isopods are in class Arthropoda (“jointed legs”). To call them the same is like saying or that a clam is the same as an octopus. (Both are in class Mollusca.) To find the isopod branch of the arthropod tree, click on Crustacea, then Malacostraca, then Peracarida, then Isopoda. (The middle picture on the Isopod page shows a parasite that enters the mouth of a fish, then eats the tongue and lives in its place.)

But what is Hovind’s point? Even if an old form persists, “cousin” groups could still have evolved from their common ancestors, and evolutionary pressures continue to operate today. Is it simply a chance for him to laugh at the foolish scientists who can tell the difference between a crustacean or a trilobite? Besides being a cheap shot, it’s a remarkably useless one.

More links:

• Here’s a very large picture of the tongue-replacement isopod, Cymothoa exigua, mentioned above.
• Here’s an article about the Giant Isopod, Bathynomus giganteus.
• Incidentally, in another group of crustaceans, the Remipedia, there’s a family called Godzillidae.

Teaching the controversy in evolution

Notoriously, over the last several years the U.S. Ohio State Board of Education tried to weaken or discredit the teaching of evolution. Deborah Owens-Fink made the original motion to teach a “two model” approach, naming evolution and intelligent design as the two models. However, scientific criticism discouraged a frontal attack. Instead, the Board proposed an educational benchmark that required,

“Describe how scientists continue to investigate and critically analyze aspects of evolutionary theory. (The intent of this benchmark does not mandate the teaching or testing of intelligent design.)”

Still, finding suitable lessons was a long process. Dr. Steve Rissing reviewed the original sample lesson considered by the board. However, most of his recommendations were ignored, and thus he came to offer the lesson at the link instead:

On 13 January [2004] I testified to the state board of education that many points in [lesson] L10H23 remained false and uncorrected even after the outside review process and that in general, the lesson was hopelessly flawed.

At the request of some members of the board, Dr. Rissing then wrote a sample lesson draft lesson plan that taught real scientific controversies that are being debated in evolution.

In a Panda’s Thumb online discussion, Richard B. Hoppe comments on the exercise:

The response was effectively (though not explicitly) that they don’t want genuine scientific “critical analysis”; they want specific canards drawn from the creationist literature. On request from several Ohio Board members, we prepared a lesson plan incorporating genuine scientific questions in evolutionary biology. It fell into a black hole in the department of Education.

So the scientifically valid lesson was quietly dropped. This is where Good Management policies and procedures would be handy for the Board. For example, one could require that the school board respond to submissions within a certain time; must give reasons for acceptance or rejection; or even must follow the advice of their expert groups unless they can state a compelling reason why not.

Relative risks

I’ve been saying this for twenty years. Women get in a panic about the risk of stroke or some other rare complication caused by contraception and stop using their contraception—thus exposing themselves to far higher risks from pregnancy and childbirth.

The Well-timed Period puts it all into perspective.

Cephalopod links

I once saw a TV show in which an octopus was presented with a globular glass jar, stoppered by a cork, with a crab inside. First the octopus dived at the crab; but when it bounced off the glass, it wrapped three arms around the glass and two aroud the cork. In about three seconds it had twisted off the cork and was happily inside, eating the crab.

Not bad for an organism with no manufactured products, no tools, no hands, and no experience of glass! … and a relative of the lowly clam.

• Octopus links
• Enchanted Learning: Octopus
• Quick (wiki) on Octopus
• Giant Pacific Octopus
• octopus news online
• octopus eats shark (Google video)
• Cephpod, the cephalopod database
• Cuttlefish mystery

The link below is to vintage pulp magazines with covers featuring an octopus.

Tags: cephalopods, squid, octopus, shark, predation, octopus intelligence, molluscs, pulp magazines,