Insects are (pan)Crustaceans and Crustaceans are paraphyletic.

[Kai]

The title is refering to a rather exciting paper which just appeared in Nature Journal a couple days ago. The authors have used 62 genes from 75 species representing all the major clades of arthropods (and therefore the greatest diversity of life on this planet) to infer a phylogeny of the Arthropoda.

The results are interesting, to say the least.

http://blogs.discovermagazine.com/loom/2010/02/10/blind-cousins-to-the-arthropod-superstars/ and

http://myrmecos.wordpress.com/2010/02/11/the-most-ambitious-arthropod-phylogeny-yet/

weigh in on the coolness of this whole paper. With the snow still on the ground outside, its like christmas for an arthropod systematist.


Some particularly interesting aspects of the phylogeny:

- Insects are clearly nested within the crustaceans, no way to bow out of it this time. We can infer that insects and other hexapods are simply terrestrial adapted crustaceans. The big problem with this for carcinologists is that it renders the crustaceans paraphyletic, so we can no longer talk about crustaceans but the clade Pancrustacea, which includes the insects.

-The closest living relatives of the insects seem to be the Xenocarida, the "strange shrimps". Time for the morphologists to go wild.

-The chelicerates, including spiders, are still a mess. I wouldn't trust any clades with bootstraps under 90 in this. The analysis has been done with maximum likelyhood, a phenetic, distance related measurement, and not parsimony. So, things like "paleoptera" I'm not willing to accept.

-It's interesting how the phylogeny largely vindicates morphologists in their earlier decisions. This seems to be a trend, and it speaks of the ability of molecular systematics to independently corroborate traditional systematics.

[Triple Zero]

insects, and creatures with exoskeletons in general, are AEWSOEM

[Kai]

Except abalone is a mollusk.

[Triple Zero]

YEAH MAN, ABALONE IS A MOLLUSK, SO YOU BETTER JUST MAN UP AND EAT IT DAMNIT

[Requia ☣]

Wait, mollusks aren't related to crustaceans?  Then why do I get nasty reactions from both of them?

[Kai]

Wait, mollusks aren't related to crustaceans?  Then why do I get nasty reactions from both of them?

They're both Bilaterian, but Arthropods (including Pancrustacea) are in Ecdyzoa, while mollusks are Lophotrochozoans, more closely related to Annelida than any of the Ecdyzoans like Arthropods and tardigrades. In other words, Mollusca is as closely related to Deuterostomes (ecinoderms, tunicates, Chordates) as it is to Arthropods, which is to say not that closely.

As for allergies, why are people allergic to only milk and fresh cut grass? *shrug*

[BabylonHoruv]

Wait, mollusks aren't related to crustaceans?  Then why do I get nasty reactions from both of them?

Maybe you are allergic to what they eat?

[Mesozoic Mister Nigel]

Wait, mollusks aren't related to crustaceans?  Then why do I get nasty reactions from both of them?

Because you're allergic to both of them?

[Bruno]

Because they hate you and wish you dead. Sinister is the mollusk.

NOOOOOO!!!! MOWWUSK WUUVZ UUUUUUU!!!
               \

[E.O.T.]

WHEN I WAS YOUNG

          It was damn fun catching AND eating crawfish.

AND NOW

          I leave the quick undesireables to my ground fowl.

THEY

          Kill. and let Cthulu sort 'em out.

[Iason Ouabache]

Awesome story, Kai. It always made sense to me that insects and arthropods were fairly closely related. I never realized that it was this close though. Seabugs, indeed!

This a bit of an awkward question to ask, but what is the most recent common ancestor between these hexapods and tetrapods? Did life start out with the 4 limbed design and then upgrade with another segment of legs to form hexapods? Or did both branch off of something more basic?

[Jenne]

mm....seabugs....dipped in garlic butter...

[Kai]

Except abalone is a mollusk.

well, they just changed Crustaceans and Crustaceans to be something else right? The horrid little fucker looks like a water snail to me D: I'm still using that line, because there is a 99.9 % chance they won't even understand it anyhow. Untill that .01 time when I try it on a biologist and get my ass handed back to me.

Yes. A mollusk. Not closely related to Pancrustacea, or Arthropoda. That understanding hasn't changed.