Tardigrades have Hox genes. They’re just missing some, and the colinear array has been scrambled around. It’s unlikely that tardigrades are the primitive condition, because that would mean that chordates, annelids, and arthropods would have had to have independently generated that middle bank of Hox genes.
The picture at the top looks like a colorized SEM micrograph. I’ve seen them in my light microscope, and they’re sort of transparent, so when you see that kind of solid look, you can trust that it was made with an em technique.
Reginald Selkirksays
I’ve seen a video of a tardigrade moving around and it looks remarkably like an electron microscope video – is this what it truly is?
got a link? EM methods work much better with vacuum, which is not especially compatible with active life.
madtom1999says
#9 Reginald – That’s what I thought but the video (which I cant find at the moment – our internet is really slow at the moment) had the EM quality – my dad was a Uni Prof in biology so I’ve seem millions of the bloody things* and they have that ‘everything in focus’ look about them and as PZ pointed out above they are see through in visible light. But it was solid and moving – seemingly quite happily – so I guess it was in an EM in a pretty perfect vacuum.
* we also had the best ever mirror in our reflecting telescope as he could use the vaporiser that was normally used to coat specimens to re coat the mirror when the coating got a bit duff!
Decades ago, our EM tech did some pretty cool observations of live insects in an SEM — it can be done, briefly. He didn’t even sputter-coat the animals, which is done in part to allow you to bleed off the accumulation of electrons that would obscure the image. You’ve only got a short time to work with the specimen, though.
Aw. Nothing about how the general hardiness of waterbears (and similarly hardy organisms, not closely related, like bdelloids) appears to be the result of adapting to desiccation.
Freaking DNA repair, how does it work?
lpetrichsays
Seems like a case of neoteny, becoming mature in what is otherwise an immature state. Most animals add segments on their rear ends, so having only a few segments is rather obviously immature state. Indeed we see that in some crustaceans. They have a larva called a nauplius that is only a few segments. It does have some legs, which it uses to swim with. As the animal grows and makes more segments, the nauplius becomes the head and its legs become antennae.
Fruit flies, like other dipterans, make their segments all at once, presumably to speed up development. I think that that is a good illustration of a risk of model systems: they may have unrepresentative features.
And for your listening pleasure while PZ prepares his video: Cosmo Sheldrake’s “The Tardigrade Song”
I love this, thanks PZ!
Zardoz! Featuring Sean Connery’s most magnificent performance!
i guess the lack of Hox Genes in Tardigrades can’t be a primitive condition?
Very nice video PZ!
Your delivery has improved a lot!
DonDueed — So your saying Sean should have made more movies in red nappies?
I’ve seen a video of a tardigrade moving around and it looks remarkably like an electron microscope video – is this what it truly is?
Tardigrades have Hox genes. They’re just missing some, and the colinear array has been scrambled around. It’s unlikely that tardigrades are the primitive condition, because that would mean that chordates, annelids, and arthropods would have had to have independently generated that middle bank of Hox genes.
The picture at the top looks like a colorized SEM micrograph. I’ve seen them in my light microscope, and they’re sort of transparent, so when you see that kind of solid look, you can trust that it was made with an em technique.
got a link? EM methods work much better with vacuum, which is not especially compatible with active life.
#9 Reginald – That’s what I thought but the video (which I cant find at the moment – our internet is really slow at the moment) had the EM quality – my dad was a Uni Prof in biology so I’ve seem millions of the bloody things* and they have that ‘everything in focus’ look about them and as PZ pointed out above they are see through in visible light. But it was solid and moving – seemingly quite happily – so I guess it was in an EM in a pretty perfect vacuum.
* we also had the best ever mirror in our reflecting telescope as he could use the vaporiser that was normally used to coat specimens to re coat the mirror when the coating got a bit duff!
Decades ago, our EM tech did some pretty cool observations of live insects in an SEM — it can be done, briefly. He didn’t even sputter-coat the animals, which is done in part to allow you to bleed off the accumulation of electrons that would obscure the image. You’ve only got a short time to work with the specimen, though.
Here’s a short article on imaging live organisms in the SEM.
Aw. Nothing about how the general hardiness of waterbears (and similarly hardy organisms, not closely related, like bdelloids) appears to be the result of adapting to desiccation.
Freaking DNA repair, how does it work?
Seems like a case of neoteny, becoming mature in what is otherwise an immature state. Most animals add segments on their rear ends, so having only a few segments is rather obviously immature state. Indeed we see that in some crustaceans. They have a larva called a nauplius that is only a few segments. It does have some legs, which it uses to swim with. As the animal grows and makes more segments, the nauplius becomes the head and its legs become antennae.
Fruit flies, like other dipterans, make their segments all at once, presumably to speed up development. I think that that is a good illustration of a risk of model systems: they may have unrepresentative features.
Looking for Tardigrade 2. It ended so abruptly!