Tuesday Crustie: Baby pictures

If you look at someone’s baby pictures, you might have a hard time matching them to photos of that person as an adult. Recognize this person?

Or this one?

And you have it easy with humans. Humans don’t undergo metamorphosis or anything. Unlike this wee beastie:

This crustacean baby was described from the stomach of a dolphin way back in 1828. Just for perspective, Charles Darwin was still in university at the time, and his voyage on the H.M.S. Beagle was still a few years in the future. Because this species had these big horns and elaborately armoured exoskeleton, it was named Cerataspis monstrosa. You can probably recognize the second half of its name means “monster.”

At the time, it wasn’t clear that this was a larva, which obviously hindered a more definitive identification. But there was a bigger problem: it was just rare. So even as new genetic techniques were developed, Cerataspis monstrosa was not found in usable condition. Bracken-Grissom and colleagues, in a forthcoming paper, seem to have had just one Cerataspis monstrosa from to take DNA from. They used that DNA try figure out if it was a larval form of a better known crustacean.

The DNA work was tricky. They tried several times to use a sequence of DNA often used for barcoding, and failed repeatedly. Fortunately, other regions of the genome worked.

Thanks to Bracken-Grissom and colleagues, we now know that that turns into this:

This is Plesiopenaeus armatus, which is a very deep water living shrimp. Bracken-Grissom and colleagues give records of it living in waters of more than 1,000 m deep.

So what of Cerataspis monstrosa? Bracken-Grissom and colleagues recommend that the larva be given the adult name – Plesiopenaeus armatus. This is not a done deal, however. The larvae got their name first, and that would mean that it would normally take precedent. The authors note that they are applying for an exception to the rule on the grounds that the adult for the genus is much more often used, so renaming the genus from Plesiopenaeus to Cerataspis would cause unnecessary confusion.

Oh, and as for the human baby pictures above? They are, in order:

Harrison Ford, and...

Tobey Maguire.

Reference

Bracken-Grissom HD, Felder DL, Vollmer NL, Martin JW, Crandall KA. 2012. Phylogenetics links monster larva to deep-sea shrimp. Ecology and Evolution: in press. DOI: 10.1002/ece3.347

Larval photo from here; adult picture from here.

Harrison Ford pictures from here.