Which animals do not have a brain?

You need a brain to live, right?  Nope!  Well, you do, but there are a fair number of Animal Kingdom cousins who don’t.  Let me introduce you to some of them!

Photo by Daniel Battershell

 

If I only had a brain…

First, a quick definition of what kind of thinking organ we’re looking for. 

The thinking that happens in our brain (conscious and otherwise) is carried out by neurons – nerve cells that process information by sending signals wherever they need to go.  A bunch of neurons gathered together directing traffic as part of the central nervous system is considered to be a brain.

A bunch of nerve cells clustered together is called a ganglion, and if it’s part of the peripheral nervous system (as opposed to central) then it’s not officially a brain.  (As a note, part of our brain is called the basal ganglia, but it’s argued that this region should be called the basal nuclei to be less confused with non-brain ganglia.)

Regardless, while some of the animals on our list may have ganglia controlling some of their functions, most of the animals here don’t even have any ganglia at all!

 

Tunicate

Commonly known as the sea squirt (that’s the cutest name!), this marine filter feeder looks and functions like a blobby straw.  It’s been around since the Cambrian Period, so it has done well for itself without a brain.

But get this – only the adult sea squirt has no brain.  A baby squirt, which is a tadpole-looking larva, actually has a tiny brain and one eye, and it can swim around but it can’t eat.  When the juvenile gets hungry enough to become a grown-up, it finds a place on the ocean floor to settle in for a filter-feeding and stationary adult life.  Once rooted, the baby squirt grows and absorbs all the parts it no longer needs, including its tail, eye, and brain!  These useless bits turn into new parts as the sea squirt becomes fully grown…and brainless.

Trichoplax adhaerenes

This creature is only a millimeter wide and it sucks up food with its underside, so we’re going to give it a break and totally excuse it for not having a brain.

This creature doesn’t have a cute nickname as of yet, but the phylum name (placozoa) means “flat animals.”  So far, trichoplax is the only species in the phylum, but we may discover more species in there as we look more closely down the road.

Trichoplax looks like a teeny, grayish, almost transparent, shapeshifting pancake.  It also needs a cute name.  Squirmy Cake, perhaps?



Photo by Bernd Schierwater …of a squirmy cake

Echinoderms

These are our good friends the sea stars, urchins, sea lilies, and sea cucumbers.  A few have ganglia, but nobody here has an actual brain.  There’s no planning ahead in the echinoderm’s daily life.

Sea lilies are rooted to the ocean floor and gather food via their five pairs of feathery arms, no thinking necessary.  The others, like the urchins, creep around looking for their food.

Sea stars have no ganglia at all, yet they have some sense of touch, smell, sight, and so forth.  Apparently, if one of the sea star’s arms smells something good, it stages a coup over the other arms’ initiatives and starts pulling the creature towards the food source. 

Sea cucumbers may be brainless, but their defense mechanisms are genius.  They can disgorge their guts and internal organs, startling and grossing out a would-be attacker.  They also can eject long sticky tubes from their anus which can ensnare and permanently disable a predator.  Disgusting but effective, which seems pretty smart to me.

Jellyfish

Instead of having a brain or even ganglia, jellyfish manage to get their business done by virtue of a neural net – a system of connected neurons interwoven around the animal’s body.

Like the humble squirmy cake, jellies can be 1 mm wide …but the big ones can get you with 100-foot-long tentacles, and some of the little ones can kill you with relative ease, so brain or not, it’s best not mess with that whole phylum.

Corals and Anemones

Like the jellies, corals and anemones lack a centralized nervous system and instead have a neural net of sorts initiating movement around the body as needed.

By the way, sea anemones, corals, and jellyfish have all digestive chambers with a single opening, which serves as both the mouth and the anus.  Just thought I’d share that.  (And put these on the list of things I’d rather not be reincarnated as.) 

Sea Sponge

Perhaps the most famous for not having a brain, the sea sponge doesn’t even have a digestive, nervous or circulatory system.  Instead, it has a bunch of unspecialized cells that can migrate around the animal’s body and transform into whatever type of cell is needed at the time.  How cool is that? 

And check it out – sponges can sneeze.  And while our human sneezes are fleeting, a sea sponge sneeze can last for 30 to 60 minutes!  This impressive feat is explained in an article here which notes, “Sponges are the only multicellular animals without a nervous system. They do not have any nerve cells or sensory cells. However, touch or pressure to the outside of a sponge will cause a local contraction of its body.”

Bivalves

These are your clams, oysters and mussels, which don’t have brains but do have ganglia, so in the company of all these other brainless creatures we can go ahead and give the bivalves some little graduation caps.

Honorable Mention for Slime

Slime mold is not a member of the Animal Kingdom and so can’t be included in this list, but it deserves mention in the annals of brainless function because, according to a study by the University of Sydney, this mold has memory!

This single cell organism leaves a trail of slime to tell where it’s been, and research has shown that slime mold is capable of anticipating periodic events and even solving mazes.  Biologist Chris Reid admits, "I, for one, welcome our new gelatinous overlords."

Google googol for lots of 0s

photo by Gerd Altmann

Kids around here recently celebrated their 100^th day of the school year by partaking in various activities revolving around the number 100.  In honor of that auspicious event, we are checking out what happens when you get 100 zeros to play follow-the-leader with a 1.

Googol!

In 1938, mathematician Edward Kasner was searching for a name for a number he had in mind to illustrate the thought-level difference between infinity and numbers that are not actually infinite but just seem to go on forever by virtue of being ridiculously huge.

The number he envisioned was 1 followed by 100 zeroes, which you can either write all the way out, or express like this: 10¹⁰⁰.  But what to name this crazy big number?

As Kasner was out on a stroll with his 9-year-old nephew Milton Sirotta, he asked the youngster for an opinion.  Milton – proper purveyor of nine-year-old wisdom (don’t underestimate it!) – thought that a pretty ridiculous number should have a funny-sounding name, so he fatefully suggested “googol.”  And it stuck.

How big is that, really?

Let me tell you, googol is big.  Googol is greater than the number of atoms in the known universe.  If you labeled the universe’s subatomic particles with sequential numbers, you’d run out of matter bits before you got to googol.

If you started counting by ones at the moment of the Big Bang and spoke one number per second from then until now, you would only be about halfway to counting to googol.

Be glad for that big number, though, for around googol is the number of years we expect to pass before the heat death of the universe -- a ridiculously long existence expressed by a ridiculously large number.

But googolplex knows what from big!

Young Milton went on to suggest an even bigger number – googolplex – which he described as writing a 1 followed by zeroes until you get tired of writing.  Kasner thought there should be a little more definition there, but googolplex ended up being plenty big indeed – it’s defined as a 1 followed by a googol of zeroes.

How much is a googolplex?  I’ve seen it described thus: take the universe and pack it full with specks of dust.  Give each speck a number assignment (1, 2, 3, etc.).  Now reassign each speck a new number.  Keep going…the amount of different numbering combinations you could get out of a speck-stuffed universe is approaching the range of a googolplex.

How about Google?

Word has it that the search engine giant got its name during a meeting when its founders were brainstorming and looking for available domain names.  To give an impression of the company’s hoped-for far-reaching web presence, someone suggested “googol,” and the person typing in potential domain names typed “google” – presumably just an outright misspelling – and that’s where Google comes from. 

Similarly the folks at Google thought it would be cute to call their headquarters the GooglePlex.  Yeah, it’s cute.

And finally…

There’s a video here that reviews all this and then shows how a universe that’s googolplex meters wide would be so big that the subatomic particles would run out of possible arrangements of themselves before running out of space to arrange in, and would therefore have to repeat some permutations exactly, resulting in your ability to have tea with yourself…if you could find yourself in a googleplex-meter-wide universe, that is.

Which extinct animals could be cloned right now?

photo by Nancy Steffens

This question draws forth images of children heading off to school each morning, riding on their saber-tooth cats, pet moas stalking along behind, dodging roaming mammoths along their way.

What is cloning, really?

Cloning is a process that makes genetically identical copies of an organism.  There is such a thing as natural cloning – this occurs with some plants and single-cell organisms which copy themselves without fertilization, and identical twins are also natural clones.  As for artificial cloning, there are three basic types – gene, therapeutic and reproductive.

Gene cloning makes copies of genes or DNA, and therapeutic cloning makes stem cells for creating new tissues.  But here we’ll be talking about reproductive cloning -- the method by which an animal can be created from material cells, such as those from skin and hair. 

The basic process is this: an egg is taken from a living animal and the cell’s nucleus is removed.  To review, the nucleus is where the DNA hangs out, which instructs the cell as to what to do with itself.  Then a cell is taken from the animal to be cloned, and its nucleus is removed and put into the host egg.  This is done either by just sucking it out with a syringe and inserting it into the egg, or by joining the two with an electric pulse.

Now you have a living animal’s egg containing a nucleus from another (could be dead) animal.  The egg is spurred into action with electricity, and after it grows to embryo size in a lab, it is placed into the womb of a related species. 

There’s a handy illustrated fact sheet about the process here.

Now you could have a kitten growing in Cat C that came from the egg of Cat B and a skin cell of Cat A.  Or a saber-tooth baby going for a ride in a lion.  Or even a Tasmanian tiger, the genes of which have been made to be produced in the fetus of a mouse -- not that the mouse in this case carried a tiger to term, but it illustrates that you don’t need to have the same kind of animal to recreate age-old genes.  Surrogate mothers for full-term, fully-formed creatures should, however, be at least somewhat related to the original species.

So thanks to the existence of elephants, we could find a surrogate mother for a mammoth, and recreating the passenger pigeon via a rock pigeon’s egg would be easy (as easy as cloning is, that is.)  But the lack of availability of a suitable womb would postpone the de-extinction of some species, notably the giant ground sloth, which will have to wait for an artificial womb because its closest living relative – the 8-kg two-toed sloth – would have a mighty hard time birthing a 1,000-kg ground sloth baby.

As for animals that have no existing relatives, there is still hope.  As recently as 2007, a method was found for reverting adult cells into embryo-like stem cells, which could then be made to produce any kind of tissue call.  So finding an egg to host is not necessarily necessary, but the technology still has a ways to go before it becomes particularly efficient.

Does it work?

Most of the time, actually, no.  Cloning has a very low success rate compared with good ol’ regular reproduction.  The first animal successfully cloned from an adult cell – the famous Dolly the sheep, born in 1996 – followed 276 failed attempts. 

While cloning from adult cells of living creatures has gradually gotten more successful, the overall baby production process is still way less efficient than letting the animals reproduce naturally, not to mention that clones have a higher propensity for health problems than non-clones. 

So as far as, say, producing livestock, cloning makes no sense.  But in the case of extinct animals, it is the only way.

So whose DNA do we actually have available to clone right now?

Creatures that died off more than a few tens of thousands of years ago are gone for good; their DNA has broken down by now.  However, animals that have gone extinct during or after the last ice age stand a chance if some of their tissue was preserved.  Ice-age creatures have been found preserved in -- no surprise -- ice, as well as tar pits, and animals that died more recently have been collected by curators of museums and labs.

The San Diego’s FrozenZoo has cells from over 1,000 different species, including critically endangered species like the northern white rhino.  Around the globe, cells are on hand that could possibly be reborn into a number of extinct species, including the recently extinct Tasmanian tiger and passenger pigeon, the giant moa, the Irish elk, and yes, saber-tooth cats and mammoths.

Also in the lineup for de-extinctable species are – ready for this? – Neanderthals.  Recent evidence has suggested that those beefy cave-dwellers were actually much more intelligent and articulate than previously believed, and it turns out that they’re not so separate of a species from us after all.  In fact, interbreeding certainly occurred, and still does, sort of – it so happens that a lot of us have Neanderthal DNA in us right now!  My own uncle recently got confirmation that he’s 2% Neanderthal, so I guess I’m in the club.  Does that explain why I lumber around so much before I get coffee?

 

Has anyone brought an extinct species back?

Yes, indeed – but sadly, not for long.  In 2003, scientists cloned a Pyrenean Ibex, the first to exist on Earth since the species’ presumed extinction in 1999.   Unfortunately, the youngster died soon after birth from a malformation in its lungs.

Still, hope is in the air, and plans are ever afoot to clone lost creatures, especially the iconic mammoth.  Japan’s Dr. Akira Iritani claims he will produce a mammoth by 2016…which is pretty optimistic, considering the general failure rate and the fact that the critter will have to gestate for a good year and a half at least.

It seemed like a good idea at the time

So should we really be doing this?

When faced with the question of whether the dinosaurs in the movie Jurassic Park should exist, Jeff Goldblum’s character Dr. Malcolm says, “Your scientists were so preoccupied with whether or not they could that they didn't stop to think if they should!”

There are those who believe that we owe resurrection to creatures that humans drove to extinction.  This excerpt from a NationalGeographic article shows the stance nicely:

“If we’re talking about species we drove extinct, then I think we have an obligation to try to do this,” says Michael Archer, a paleontologist at the University of New South Wales who has championed de-extinction for years. Some people protest that reviving a species that no longer exists amounts to playing God. Archer scoffs at the notion. “I think we played God when we exterminated these animals.”

There is also the belief that we should carry on with cloning because, well, we can.  As Insung Hwang of the Sooam Biotech Research Foundation says, “The thing that I always say is, if you don’t try, how would you know that it’s impossible?”

Some reasons to reconsider just up and cloning everything include concern about the survival of the animals once they’re back on Earth.  For some species, their former habitat is greatly reduced or entirely unavailable.  Alternately, some species whose habitat is intact may pose a threat to the ecosystem that has established itself since the animals’ departure, making the extinct species now an invasive one.

Others believe that resources would be better spent focused on the preservation of existing endangered species.  Cash goes a lot further in environmental preservation efforts than it does in the realm of low-success-rate cloning.  Proponents of the focus-on-the-now crowd also see cloning as better used to preserve tissues and attempt to clone living endangered animals before working on those that are already extinct.

The seven-year-old who brought up this question thinks that science should certainly try to clone some extinct species, but cautions against reviving the “dangerous” species of the past.  “Wooly mammoths could be stomping on and destroying everything…and saber-tooth tigers would do damage to alive creatures.”  I can see some wisdom in that.

Truth, bro.

But really, pros and cons aside, wouldn’t it just be neat to see some ice age megafauna cruising around in the flesh?  Hank Greely, a leading bioethicist at Stanford University, agrees:

“What intrigues me is just that it’s really cool,” Greely says. “A saber-toothed cat?  It would be neat to see one of those.”

Especially if we could ride it to school.