Do spiders dream of arthropod sheep?

You ever watch a sleeping cat or dog, and see their little paddy-paws twitching and their legs all curled up? Cute, isn’t it? You can just imagine they’re dreaming.

Spiders do it, too.

Jumping spiders are special because, unlike most arthropods which have fixed eye positions — they have to turn their heads to change their field of view — they have telescope eyes which can swivel, so you can actually see their eyes move while they are presumably sleeping. This has led some investigators to suggest they have a kind of REM sleep.

Sleep and sleep-like states are present across the animal kingdom, with recent studies convincingly demonstrating sleep-like states in arthropods, nematodes, and even cnidarians. However, the existence of different sleep phases across taxa is as yet unclear. In particular, the study of rapid eye movement (REM) sleep is still largely centered on terrestrial vertebrates, particularly mammals and birds. The most salient indicator of REM sleep is the movement of eyes during this phase. Movable eyes, however, have evolved only in a limited number of lineages—an adaptation notably absent in insects and most terrestrial arthropods—restricting cross-species comparisons. Jumping spiders, however, possess movable retinal tubes to redirect gaze, and in newly emerged spiderlings, these movements can be directly observed through their temporarily translucent exoskeleton. Here, we report evidence for an REM sleep–like state in a terrestrial invertebrate: periodic bouts of retinal movements coupled with limb twitching and stereotyped leg curling behaviors during nocturnal resting in a jumping spider. Observed retinal movement bouts were consistent, including regular durations and intervals, with both increasing over the course of the night. That these characteristic REM sleep–like behaviors exist in a highly visual, long-diverged lineage further challenges our understanding of this sleep state. Comparisons across such long-diverged lineages likely hold important questions and answers about the visual brain as well as the origin, evolution, and function of REM sleep.

If this were happening in a cat or a dog we’d easily assume the behaviors were a reflection of whatever they were dreaming about. It would be nice to imagine this was just as true of spiders, but I’m going to be slightly skeptical of the idea that the behavior is indicative of “dreaming” or even analogous to REM sleep. The authors are cautious, too.

The complex visual and cognitive behaviors of salticids and their relatively small nervous system facilitate experimental tests of the role of visual experience in REM sleep–like retinal movements. Eye movement patterns during REM sleep have been hypothesized to be directly linked to the visual scene experienced while dreaming—begging the deeper question of whether jumping spiders may be experiencing visual dreams. This raises a unique opportunity to test this “scanning hypothesis” in jumping spiders, where retinal movements can be observed. Since visual input can be controlled in jumping spiders early on (unlike in humans), retinal responses to repeated visual stimuli presented during the day might partially reappear during REM sleep–like states.

The problem I have is that we don’t know all that is going on in the brains of humans during dreaming or REM sleep — so how can we compare that to what spiders experience? A deeper analysis of the activity of the nervous system would be needed to do a good comparison, and this paper is only looking at behavior.

An alternative to “dreaming”: spiders go through waves of alertness during sleep. At some levels, they are awake enough to monitor their environment, so those eye movements aren’t a consequence of dreams — that’s the spider doing sentry duty, scanning what’s around it to search for prey or threats. The movements tell us nothing about the inner life of a spider, only that it wants to eat or avoid being eaten. You know they don’t have eyelids, right? They aren’t as blind as we are while sleeping.

That doesn’t mean the behavior lacks any homology with vertebrates. Maybe our REM sleep is also a consequence of the evolution of rising and falling levels of alertness, and dreaming is just a side effect of brains randomly invoking patterned activity on top of all that.

If spiders dream, though, I do wonder what bloodthirsty scenarios are playing out in their heads. That may also be similar to vertebrate dreaming — I don’t think my cat dreams of frolicking in fields of dandelions, but of ripping the heads off smaller mammals. But that’s my psycho cat.

It doesn’t work on spiders

Mary told me I should mention this app, Merlin Bird ID, in case you don’t already have it. You fire it up, click on a button, and it just listens and tells you what birds it hears. I got it a while back because the crazy early morning bird cacophony was bugging me — at least I ought to know who’s shrieking at me early in the morning. I can sit in my office and have it inform me what all the noise is about. This morning it was black-capped chickadees chattering away, blue jays and redwinged blackbirds making a ruckus, and an American robin fussing about. It’s not as bad as it was earlier this summer, because we also have a Cooper’s hawk hanging about in the neighborhood. When it squeaks, it gets quiet, briefly.

Hey, I’ve noticed fewer squirrels making pests of themselves lately. I wonder if I should play recordings of a Cooper’s hawk when they start climbing the bird feeder and scrabbling at my window. (Before you say squirrels are pretty clever and will just learn to ignore the noise, that’s part of the plan: they’ll become more vulnerable to hawks then.)

If you’re more of a visual person, I’ll also recommend Seek from iNaturalist. Put that on your phone, aim it at any organism, and it’ll use the iNaturalist database to let you know the scientific name of what you’re seeing. It’s very handy. It even works on spiders, unlike the Bird ID program.

Metabolism First! And the origin of life

Two and a half weeks until classes resume, so I’m shifting brain gears to get excited about cell biology again. One of the tools I use to get into the right mindset is reading more biochemistry, and lately that means reading more Nick Lane, who is one of those biochemists who is obsessed with evolution and does a marvelous job of integrating the finicky little details electrons and protons and small molecules and chemistry with the big picture of where all this comes from and how it has shaped life.

I’ve read and reread Lane’s latest book, Transformer: The Deep Chemistry of Life and Death, and recommend it highly. I’ve been struggling with how to explain it’s contents, and it’s not easy — in my class, I spend weeks just gradually building up the background needed to understand the chemistry of the cell, which makes it hard to dump on a blog or a single video as anything but a huge indigestible bolus. And of course it took Lane 400 pages in a densely packed book to cover it all.

I should have known I could just let Nick Lane do all the hard work.

“KREBS CYCLE” is not a phrase that usually gets students excited — I know from experience — but this is juicy stuff. The talk itself covers a huge amount of ground, giving the basics of metabolic cycles and going into the origins of life and the great leap forward provided by mitochondria in endosymbiosis, and the diverse ways various organisms have taken the basic toolkit of the Krebs cycle and used it in novel ways. That’s all good solid science, and I don’t understand how anyone can have any doubts about the general chemistry that leads to life (well, I sorta do — they don’t know any biochemistry. All the YouTube debates about the origin of life are a waste of time, given that creationists are disgracefully ignorant of even the most rudimentary understanding of biochemistry).

Near the end, he gets farther out into weeds with speculation about aging, cancer, and consciousness. It’s interesting and he could very well be right — he’s a smarter man than I am — but the ideas range from very likely (metabolic shifts as agents of senescence and cancer), to potentially revolutionary but still on the fringe (the role of calcium and membrane potentials in Alzheimers), to some that, well, sound like how a biochemist would view neuroscience, for instance claiming that consciousness is a product of the electrical potential across the membrane of a cell, which is rather too reductionist for me.

Watch the video, though. If there are bits that you find heavy slogging, or just too out there to grasp, let me know in the comments. That’s information I can use to present these ideas to a class of second year students. And if you find it really deeply enlightening, go out and read Transformer. It contains a lot of the ideas about cellular metabolism I’d like to get across to my students.

It would make my life a whole lot easier if I could just show a one hour video that explains everything, then say, “Well, that’s all done then. We spend the rest of the semester reading poetry and dancing and playing video games! Yay!” I suspect I should probably fill in a lot more background and talk about the details, but maybe the video would be a nice dessert for the end of the semester. I’ll have done my job if all the students can watch it and say they already knew all that, but that Lane did a fine job of tying it all together.

Sorry, everyone

You like me! You really like me!

Yesterday’s short video clip of maggots has turned out to be surprisingly popular, second only to my most recent video about Jordan Peterson. This means that I seem to have found my YouTube niche: making videos about horrible, repulsive creatures that make viewers want to vomit. I’ve also gotten requests to make more. This was not expected.

Making more Jordan Peterson videos is too much for my stomach, so now I’m thinking about ways to lower a good camera into the slime pit without risking wrecking a good lens. Maybe a cheap old kit lens with some extension tubes? I’m also going to have to puzzle out a way to adapt a tripod to look downward, because I don’t want to do it hand-held for a half hour.

You never know when someone might want some good quality B-roll of maggots, you know!

The most horrible video I’ve ever made

This will be popular, sure.

My compost bin is extraordinarily productive in producing maggots, which makes the spiders living in there very happy. The resolution here isn’t great — I used my el cheapo camera, since I was plunging it down in close to the writhing mass of larvae. If anyone insists, I suppose I could redo this with a reasonably good macro lens.

Everything is real time — no time-lapse. That’s how fast they move! Also, listen carefully and you can hear them eating. It sounds a bit like soggy rice krispies.

It’s only a minute long, so don’t worry, it ends quickly. If anyone also insists, I could record a much longer video.

No one will insist.

I know this will make some people queasy, so I’m hiding it below the fold.

[Read more…]

A different perspective

Many spider papers feature detailed closeups of their genitalia, because genitals are often diagnostic of the species. They’re often weird and twisty and convoluted, which is pretty cool. Unfortunately, they often focus exclusively on the palps, the male genitalia because they’re entirely external and easy to see and the female side of things get short shrift. It’s the same for humans!

So here you go! If you ever wondered about the internal shape of the vagina, it’s been done.

How strange. It’s roomier than I expected. There’s also a series of photos that show the variations. Neat!

For those who missed it yesterday

Here’s that image from the NASA press release yesterday.

That’s spectacular, even as reduced for the blog. You can see the whole full sized image at NASA.

What’s amazing about it is that the gravitational lensing is so obvious that even a biologist can see it. Notice those stretched and curved galaxies that form a kind of whorl around the center of the image? That’s not a camera artifact, it’s caused by a galaxy in the foreground bending light making the 4 billion light-year trek from the source to the telescope. This is beautiful stuff. Phil Plait explains it far better than I can, even if in that article he’s using a blurry image from Hubble. Blurry compared to this one, that is.

Unfortunately, I didn’t learn that from the press conference. I picked it up from all the astronomers and physicists talking about it on Twitter. The press conference was incompetence personified.

After 45 minutes of waiting with the most irritating hold music NASA could produce, the screen opened on a group of people with a poorly resolved black square in the background, the image above. You couldn’t see much of anything, because most of the screen space was dedicated to making sure you could see the old people talking about it. Kamala Harris and Joe Biden said some platitudes that mainly amounted to being so proud that the speckled black square in the distance was the product of American ingenuity, while NASA Administrator Bill Nelson talked about how very far away those lights were. It was soul-deadening stuff that told me nothing about what I was looking at. See that short paragraph about lensing that I scribbled out above? Pitiful as it is, that says far more about the image than anything in the press conference.

I watched a little bit of NASA TV before they put me on ear-grating hold, and one thing I learned is that a bunch of engineers, politicians, and administrators are terrible at putting on a show. I’ve seen better production values from amateurs (not me, of course, I suck) putting home-produced videos on YouTube. They also seem to think that crackly fuzzy flattened audio on everything makes them sound authentic.

A suggestion to NASA: next time you advertise a dramatic reveal of some gorgeous discovery, tell all the bureaucrats to stay home. Don’t book any of the politicians, who won’t know what they’re looking at, and will think it’s reasonable to delay the whole event for some other issue of statecraft (they should do that, and shut up about science). Instead, bring on a small team of scientists who will express their blissful joy at what they see, and will help us understand why this is so cool.

That’s Science Communication 101. NASA doesn’t get it. It’s a bit embarrassing how bad they are at it.

Looking forward to seeing stuff from the [PLACEHOLDER] Space Telescope today

This afternoon (2pm PT, 5pm ET) NASA will reveal the first images from their new space telescope. You can see them on their live stream (this is a continuous stream, and you could start watching right now for six hours before you’ll see the expected stunning images).

Now I don’t know what to call the Giant Space Widget. It’s been officially named after an administrator and homophobe, rather than a scientist, and I’d rather not use that name at all. To see why, maybe you could fill some of the time you’re waiting by watching this video:

I’m looking forward to the images, but I’m going to have to refer to it as the [PLACEHOLDER] Space Telescope, unless someone has a better name. Why is it named after a homophobic bureaucrat anyway?