Paedocypris

I saw on Muton, and several readers have mentioned it to me, this article about the world’s smallest vertebrate, fish of the genus Paedocypris. It’s a gorgeous translucent cyprinid, so is somewhat related to my favorite fish, Danio rerio. They live in cool, slow moving water in peat swamp forests of Southeast Asia. One female, only 7.9mm long, contained about 50 eggs, so they know it was sexually mature.

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Living Paedocypris progenetica, CMK 18496, (a, b) male, ca 9 mm; (c) female, ca 8.8 mm.

That size isn’t at all shocking—my zebrafish larvae at about that size are active hunters with functioning visual systems, capable of coordinated bouts of swimming, and they’re also very impressive animals…but they don’t have sex. It takes about 6 months for zebrafish to reach sexual maturity, and they are several centimeters long at that point. I would love to know how old these fertile Paedocypris were, but they were captured in the wild and virtually nothing is reported about their behavior or lifecycle. Ah, to have a fish colony that could be raised in a set of beakers, and could produce a couple of generations of crosses in a single semester…

One other clue that these are fully functioning, sexually mature adults are the presence of some pelvic specializations. Males have a hook and flange widget on their pelvic fins, and an odd prepelvic knob. Again, though, without knowing anything about their behavior, we don’t know how these are used in mating and courtship. Wouldn’t it be cool to put a pair under my Wild M3 scope and watch courtship and mating?

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(a) Paedocypris micromegethes, paratype male, ZRC 49869, 10.4 mm; pelvic fins, anteroventral view, showing hook and flange on anterior ray. (b) Paedocypris micromegethes, paratype, male, BMNH 2004.11.16.1-40, 10.9 mm, ventrolateral view on hypertrophied pelvic arrector and abductor muscles marked by asterisk symbols. (c) Paedocypris progenetica, paratype male, ZRC 43199, 8.5 mm, scanning electronic micrograph of pelvic region in ventrolateral view, arrow points to keratinized prepelvic knob.

Of course, in addition to not knowing their generation time yet, these fish have another drawback relative to zebrafish: tiny eggs. They extracted a range of sizes from the ovaries, but assuming the smallest are immature, they max out at around 0.3mm diameter. That’s respectable, but Danio eggs are about 1mm in diameter.

Can you tell I’d love to get my hands on a bunch of these little fish? Unfortunately, I’ve heard from fish importers that it is agonizingly expensive and time consuming to bring wild tropical fish into the country, and for good reason: to block invasive species, to prevent the spread of new fish diseases, and also to discourage the plundering of native populations. I may not ever see one of these animals, short of making a trip to Malaysia, and even then I won’t be bringing any home.

Comment problems?

I just got hit by a major wave of comment spam, and it took me while to puzzle out all the tools available in this MT system to purge them. I’m tinkering a little bit with comment settings to try and prevent it from happening again (tip: don’t put lots of links in comments, because they will get held up for my approval before posting), and I’ve clicked a few checkboxes in the settings on. If things get freaky and it doesn’t let you comment, send me an email and I’ll try to fix it.

Textbooks and Haeckel again

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[When I started this weblog, one of the hot topics in the Creationist Wars was Jonathan Wells, a Moonie who had trained as a developmental biologist and written a screed against evolutionary biology titled Icons of Evolution. This book purported to document serious flaws in some of the major examples of evolutionary biology, although what it actually did was parrot old creationist arguments and get much of the science wrong. One of the subjects he focused on was the pharyngula—the embryonic stage that exhibits a common morphology across all vertebrates. This fascinating developmental period has an unfortunate history, in that Ernst Haeckel published some fraudulent drawings of it, and also made exaggerated claims about it. One of Wells’ strategies was to condemn every biology textbook that illustrated homologies in pharyngula stage embryos, tarring them with the broad brush of Haeckelism. This got to the point where he was absurdly damning books that even included photos of embryos, and one of the things I’ve tried to do is document the way he misrepresents science teaching.]

I got a request to document some of Wells’ claims from his execrable book, Icons of Evolution. Specifically, Wells chastises several textbook authors for using modified versions of Haeckel’s drawings:

Starr & Taggart, 10th ed and this was mentioned in
Well’s testimony, p. 315, “slightly simplified version of
Haekel’s original fraudulent drawings”

Raven & Johnson, Biology, 6th ed

“modified version … exaggerates actual similarities” p. 450

I don’t have all of the textbooks he describes, but I do have the 5th and 9th editions of the above books, and I suspect the figures haven’t changed. Below, I’ve scanned in several of the figures that Wells finds objectionable, and for the most part, they aren’t bad at all, and actually make useful pedagogical points. I suspect that the real reason Wells and other creationists dislike them is that they reveal deep homologies that support evolutionary explanations of the origins of animal diversity.

[Read more…]

Another religious assault on education

Conservative religious groups are once again making grade school textbooks the battleground. In California, supremacists and revisionists are trying to make radical changes to kids’ textbooks, inserting propaganda and absurd assertions that are not supported in any way by legitimate scholars. The primary effort is to mangle history, but they’re also trying to make ridiculous claims about scientific issues.

Such as that civilization started 111.5 trillion years ago, and that people flew to the moon and set off atomic bombs thousands of years ago.

(OK, everyone, let’s all do our best imitation Jon Stewart double-take: “Whaaa…??”)

Yeah, these aren’t fundamentalist Christians, but Hindu nationalists with very strange ideas—still, it’s the same old religious nonsense. Two groups, the Vedic Foundation and Hindu Education Foundation, have a whole slate of peculiar historical ideas driven by their religious ideology, and are pressuring the California State Board of Education to modify textbooks. They want to recast Hinduism as a monotheistic religion, whitewash the caste system and the oppression of women, and peddle racist notions about Aryan origins.

This is what happens when religious dogma is allowed to dictate educational content—reality and evidence and objective analysis all become irrelevant. The earth is neither 111.5 trillion years old, nor only 6,000 years old, and the errors and misperceptions of old priests are not a sound foundation for science. It doesn’t matter whether those priests spoke Sanskrit or Hebrew, since their ideas are the product of revealed ‘knowledge’ rather than critical, evidence-based research, they don’t belong in a public school classroom.

Heck, what am I saying? It’s just another idea, right? Let’s teach the controversy and allow orthodox Hindu supremacists to battle it out with fundamentalist Christian dominionists in front of sixth graders. It should be exciting and enlightening.

(via Butterflies and Wheels)