Sunday, 4 January 2015

Moss Animals - Prefab Sprouts Of The Animal Kingdom?

Further to yesterday's conversation about oysters, a brief exchange about jellyfish ensued and I suddenly remembered these:

"Flustra foliacea" by Hans Hillewaert - Own work. Licensed under CC BY-SA 4.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Flustra_foliacea.jpg#mediaviewer/File:Flustra_foliacea.jpg

You'll probably have seen these washed up on beaches and thought they were a kind of seaweed.  They're really, really not.  This is hornwrack, Latin name Flustra foliacea, and despite its name it's a colony of small animals, about the size of mites, known as a moss animal, bryozoan or ectoproct.

They also live in fresh water.  Here's Cristatella mucedo:

"Cristatella mucedo 2014 11 10 a14" by Lamiot - Own work. Licensed under CC BY-SA 4.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Cristatella_mucedo_2014_11_10_a14.JPG#mediaviewer/File:Cristatella_mucedo_2014_11_10_a14.JPG

This is often mistaken for a string of pond snail eggs, and in fact I may just possibly have made that very mistake.  Again, it's a colony of small animals related to hornwort.  Unlike hornwort, though, the whole colony can creep along very slowly.

Some other ectoprocts look like this, but are less blurry:



(I can't attribute this image as the author of the book didn't).

These animals are about as far as you can get from something looking like a sloth or an aardvark, which might be why they tend not to be thought of as animals at all, and they do various things quite like the way plants do as well.  They are also very strange in a variety of ways, one of which is the way they excrete waste.  Whereas many animals produce stools which they then expel from their bodies, and incidentally that's not pure excretion because some of that has been eaten and hasn't changed, ectoprocts do something quite different.  Oddly, because "ectoproct" refers to the fact that they have an anus outside a ring of tentacles on each little animal, or "zooid", rather than inside it like the entoprocts:

(My drawing, sorry it's such a mess.  Incidentally, although I haven't used the technical terms for the labels, I have in fact labelled them as what they are).

An ectoproct colony is a collection of these.

You can see the anus clearly labelled.  However, rather than using that normally, what zooids actually do is fill up with excrement until it poisons them, then they die, then a new animal grows around the stool/corpse and ends up pushing it out through its anus.  Therefore, in a way ectoprocts give birth to the dead bodies of their parents.  I find this delightfully bizarre.

Other somewhat surprising things about ectoprocts mainly relate to how they're plant-like.  They capture sperm in their flower-like rings of tentacles which then fertilise their internal eggs, which I think is pretty similar to pollination of flowers.  They also overwinter as little seed-like forms called statoblasts, from which new colonies grow in the spring.  I mean let's face it, these animals have a bit of an identity issue, haven't they?  They seem to have forgotten they're animals at all and when people see them they think they're something other than what they are, such as strings of snail eggs or seaweeds.  However, they are in fact animals.  There's also another lot of unrelated animals like these called the entoprocts, which do the same kind of thing, and it took people a long time to realise they weren't just the same kind of animals, but they aren't.  Then again, if they're both animals masquerading as plants, plants are pretty distantly related to either of them, so maybe it's not that surprising that if one lot of animals ends up like this, a completely different lot will too.

What that means, in fact, is that somewhere in the space of ways in which living things can be, there's a kind of "planthood", and therefore we can probably expect other planets to host the likes of flowers, moss, seaweed and the like, except that on those other planets it might be that that they're all animals while the vegetables rampage about the landscape munching them up for dinner.  Nonetheless I won't be having them for dinner, partly because I doubt they're good conversationalists, oh, except that the entoprocts actually phone each other up, but that's another story (I'm not kidding by the way) and one which is only slightly more interesting than one of their interminable phone calls, so I'll leave it for now.

If there is some kind of abstract blueprint for plant-like things out there somewhere in the mind of the Atheon, who knows what else there might be.  Maybe a gender stereotype blueprint?  Or a pinkprint even?

Anyway, that wasn't what I was going to talk about with moss animals.  This is.  As a child, I can remember seeing hornwrack on the beach and wondering how it managed to make food considering it wasn't green, red or brown and of course the answer was that it didn't make food because it wasn't seaweed.  More confusingly though, another thing I did as a child, before I was veggie obviously, was to fish what I thought were strings of snail eggs on river weed out of the water and look at them under the microscope to see what I thought were snail embryos.  But did I?  How do I know I wasn't looking at moss animal zooids?  My memory is good enough for me to recall that the things I was looking at were dark against a light background and moving in a manner I thought suggested they had hearts, but for all I know they might have been zooids.  I doubt they were, but that's because it's too interesting, so that's like doubting the sound of hooves is zebras rather than donkeys.  So for me, this is partly about memory being unreliable and my resistance to the temptation to believe I experienced something more exotic than I really did.

Talking of exotic, another thing about ectoprocts is that they're the largest minor phylum.  A phylum is the largest classification of animals below the animal kingdom itself, not counting all the "sub" and "super" things like subkingdoms and superphyla.  It generally represents a broad body plan, so for example vertebrates are a subphylum and molluscs are another.  In keeping with something like the 80:20 rule I've mentioned before, there are a few really big phyla and loads of really small ones.  The really big phyla are the chordates (including the vertebrates), echinoderms, annelids, molluscs, arthropods, nematodes, platyhelminthes, cnidaria and the porifera (sponges) - I don't think I've missed any, but fewer than ten anyway.  Then there are the so-called minor phyla, of which there are probably about forty or fifty.  Some of these are really tiny, such as the priapulids, which have maybe eight species altogether compared to, say, more than a million species of arthropods, although they used to be more common.  There's a big gap between the big phyla and the minor phyla in terms of numbers.  One of the minor phyla, the brachiopods, used to be one of the big players before it got successfully competed with by the incredibly similar bivalve molluscs, and the priapulids used to be quite common too, but the rest always seem to have been small.  Of the minor phyla, the biggest is in fact the ectoprocts.

Naturally, I find ectoprocts interesting, and this reflects something about the way my brain works because of course ectoprocts are a minor phylum, albeit one big enough for a child to come across fairly regularly.  In fact, I find I always do this in other areas of my life.  The musical equivalent of moss animals seems to be Prefab Sprout, and like moss animals their music tends to be associated with irony.  Somehow, I always seem to back the loser, with the result that my interests tend to be obscure and arcane despite my best efforts.  This pervades my whole life.  I don't actually care, although it can be mildly annoying, but nor do I understand how it happens.  Birdwatching, for example, I find very boring because birds are too ordinary to be interesting.  Bryozoa, on the other hand, I find utterly fascinating.  The Beatles are good, and of course I like Abba, but I also like Prefab Sprout and Steely Dan, and I cannot see why others don't.  In science fiction, well, I've read a bit of Heinlein but my real favourite is Olaf Stapledon.  With painting, I don't particularly like Picasso but I love Roberto Matta.  And I am not doing this on purpose, honestly.  What's that about?