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Tuesday, 26 June 2012

Flatworms at a glance

Yes, been busy again.  The other day, though, I found a land planarian, so I thought I would dig out a section of the book that was cut, mainly because flatworms or planarians can be hard to find unless you know where to look. The one on the right is the type that lives in water,

These are just very small flat worms, and more common in fresh water than you may think. In the wild, flatworms that live in water avoid the light, so they are usually found attached to the under-side of stones or twigs, and they will often be in groups. They typically have a pointed tail-end and an arrow-shaped 'head' end, with two very primitive eyes, little more than two light-sensitive patches. Most of them are less than 10 mm long.

A land planarian looks sometimes looks like this, with a sort of "shovel" head. For some odd reason, people don't call them "land flatworms".  Posh people call them terrestrial planarians. (I put that in there for the search engines).

Land planarians have a much longer body, up to 300 mm long. They also have a shovel-shaped head, and they travel on a layer of slime like a snail or a slug. The slime is amazing stuff, because it hardens, and if a land planarian goes over a drop, the one species I have played with is able to lower itself down on a thread of hardened slime, like a spider descending on its web. The body gets much longer when it is stretched by gravity as it dangles. On the flat, they are about a third as long.

Land planarians will eat earthworms so they can sometimes be a problem in worm farms (which means you may find them in a worm farm!), but they also eat a wide range of other garden 'meat', including slugs. If you leave a small piece of meat in some leaf litter, inside some sort of cage to stop larger animals getting at it, you may attract a land planarian, though this has never worked for me. This one was on a brick wall and quietly consuming a small millipede. For scale, the picture covers a space about 10 mm high.

Notice the slime here (if you click on the picture, you should see it full-size). I think this is how they digest their food.

The last reliable count that I have seen, made in 1999, showed 822 species of terrestrial flatworm around the world. The world's greatest variety is seen in mainland Australia, Tasmania and New Zealand.

But why are flatworms flat? Probably, so they can breathe! With no lungs, blood or circulation, oxygen has to diffuse in through their skin to reach all of their cells, but the gas is all used up before it gets more than about 0.5 mm from the surface, limiting their thickness.

Flatworms will regenerate (grow back missing bits) if you chop them in halves through the middle with a sharp razor blade. It is also possible to split the "head" lengthways between their primitive eyes, and produce a two-headed flatworm. This requires a sure hand, and it is unkind. Both ends of a cut worm will grow the missing end, and both ends of a trained worm were once supposed to recall a lesson taught to the whole worm, though most people no longer believe this.

Flatworms are photonegative (light-avoiding) so they need to be kept in opaque containers with covers. With the water ones, change the water regularly, feed them once a week on chopped raw beef liver or hard-boiled egg yolk, and take out the left-over food with a pipette after a few hours. Apparently they do not often reproduce sexually in captivity, but do occasionally produce orange "cocoons" that hatch out a month or so later. They also reproduce by fragmentation, even when nobody chops them up.

I have caught aquatic planarians in the past by scooping up some drain mud and putting it in a white dish, then waiting for the mud to settle, at which point, they leave tracks in the mud that you can see. Happy hunting!

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This blog covers quite a few different things, so I tag each post. I also blog about history, and I am currently writing a series of books called Not your usual... and the first two have been accepted by Five Mile Press, The offcuts appear here with the tag Not Your Usual... . For a taste of Australian tall tales, try the tags Speewah or Crooked Mick.   For a miscellany of oddities, try the tag temporary obsessions. And language us covered under the tags Descants and Curiosities, while stuff about small life is under Wee beasties.

Thursday, 14 June 2012

Rashomon times 2 (or 2 plus 1)

OK, there was a bit of a hiatus there, mainly because I have been busy with Other Stuff.

In particular, I have been concerning myself with Australian history, in a work for younger readers. It's actually one of a series, written with the view that even complex issues can be handled by young minds, given the right presentation.

In Akiro Kurasawa's classic film, Rashomon, one story, about a murder, is told by four people: the bandit, the wife, the samurai and the woodcutter.  It is fictional.  Each version is different.

Well, I have a similar multi-version story, but it's from real life.  It involves an incident where nine versions are given by eight people, and they are all subtly different about the number and type of animal, the date (some are less specific) and in some cases, the owner(s) of the stock which were killed by a lightning strike, not long after the first white people came ashore in Sydney in 1788. The animals were in a pen (or shed) under a tree, and it seems they all perished: this was a bit of a disaster.

We are taught to pay attention to primary sources, but what are we to make of these discrepancies in first-hand accounts, written on the spot?  Perhaps some of it was due to editing or the careless making of "fair copies"?

I have done some colour-coding in the text to help you spot the variations.
In February, the weather was sultry, with lightning, thunder, and heavy rain; this sort of weather continued for a fortnight, with few and very short intervals of fair weather; a flash of lightning fell one night near the camp, and struck a tree near to the post of a centinel, who was much hurt by it; the tree was greatly rent, and there being at the foot of it a pen in which were a few pigs and sheep, they were all killed. 
John Hunter: An Historical Journal of the Transactions at Port Jackson and Norfolk Island, chapter III

Ere we had been a fortnight on shore we experienced some storms of thunder accompanied with rain, than which nothing can be conceived more violent and tremendous, and their repetition for several days, joined to the damage they did, by killing several of our sheep, led us to draw presages of an unpleasant nature. 
Watkin Tench: A Narrative of the Expedition to Botany Bay, chapter XV.

The month of February was ushered in by a very violent storm of thunder and rain. The lightning struck and shivered a tree, under which a shed had been erected for some sheep, and five of those animals were at the same time unfortunately destroyed by it. 
Arthur Phillip, The Voyage Of Governor Phillip To Botany Bay, chapter VII.

2nd February. This morning five sheep, belonging to the lieutenant-governor and quarter-master, were killed by lightning under a tree, at the foot of which a shed had been built for them. The branches and trunk of the tree were shivered and rent in a very extraordinary manner. 
John White  Journal of a Voyage to New South Wales.

Abt. 12 o'Clock in the night one severe flash of Lightg. struck a very large tree in the centre of the Camp under wh. some places were constructed to keep the Sheep & Hogs in: it split the tree from top to bottom; kill'd 5 Sheep belonging to Major Ross & a pig of one of the Lieuts
Arthur Bowes Smyth, A Journal of a Voyage from Portsmouth to New South Wales and China - in the Lady Penrhyn, entry for February 6.

On the First Day of this Month, We had a vast deal of heavy Rain. Thunder & Lightning, and the next morning 5 Sheep, 1 Lamb. & 2 Pigs, were found dead, lying under a Tree, which was riven in a violent Manner by the Lightning... 
George Worgan, Journal of a First Fleet Surgeon, entry, Tuesday 5th February. (SEE NEXT!)

We have reason to apprehend that much Mischief may be done by Lightning here. Indeed we have experienced its fatal Effects since we have been here, for one Night 6 Sheep 1 Lamb, & 2 Pigs that were lying under a Tree, were all killed and the Tree violently riven. 
George Worgan, Journal of a First Fleet Surgeon, 'Climate'.

In the night of the 6th February, six sheep, two lambs, and one pig, belonging chiefly to the lieutenant-governor, having been placed at the foot of a large tree, were destroyed by the lightning. 
David Collins: An Account of the English Colony in New South Wales, Vol. 1, chapter I.

Thursday 7 where I went to Supper being ask my God how it did thunder and Lighting - was very much frightened for the Centinell before Majr. Ross markee while we were at Supper was knock down with it - I thought at first that he had been Struck by the lighting as he came running and making a great noise and fell flat dount at my feett but he was not hurt but I am Sorry to find that by the very hard clap of Thunder the lightning Struck one of the Trees near where we were at Supper and Kild Six Sheep 2 Labms and one Pigg belonging to Major Ross
Ralph Clark, Journal.

Before you ask, Major Ross was the Lieutenant-Governor.

The spelling, especially in Clark's case, represents what the writers wrote.  People didn't have the same hang-ups about spelling back then.

I think there are some interesting conclusions to be reached from studying this, but probably not in a book for 10-year-olds, so I am sharing it here.  If you are a teacher, please feel free to use this, any way you like.

Technical and teacherly matters
There is no copyright on any of this.  If you want to view good copies of the journals, most of these can be sourced from the University of Sydney's SETIS site.  Select the Browse—All link on the left, and then look for the ones where a PDF is available, and either read or save it.

Another source that I have used is Project Gutenberg. That has given me:

  • Arthur Phillip, The Voyage Of Governor Phillip To Botany Bay;
  • John Hunter: An Historical Journal of the Transactions at Port Jackson and Norfolk Island;
  • David Collins: An Account of the English Colony in New South Wales, Vol. 1;
  • David Collins: An Account of the English Colony in New South Wales, Vol. 2;
  • Watkin Tench: A Complete Account of the Settlement at Port Jackson;
  • Watkin Tench: A Narrative of the Expedition to Botany Bay;
  • John White  Journal of a Voyage to New South Wales;
  • George Worgan, Journal of a First Fleet Surgeon.
  • Ralph Clark, Journal.

I have cleaned all of these up, using macros in Word, and pasted them into a single file. Then I added these journals in whole or in part from transcripts on the State Library of NSW site: those may be copyright, but my copies are purely for personal research.

  • Smyth  (from State Library of NSW);
  • Bradley (part, from State Library of NSW);
  • Easty  (part, from State Library of NSW);
  • King  (part, from State Library of NSW);
  • Nagle  (part, from State Library of NSW).

These journals and extracts are all in the one big MS Word file (1300 pages, almost a million words).  Each volume has a Heading 1 header, the chapters are Heading 2, and extra markers (for example, when somebody reaches Rio) are Heading 3. This allows me to navigate using Document Map.

And search. The trick is, when I search on some key word like Wilson*, sheep, lightning or salt, I can quickly find the stuff I want.  I had noticed that there were several versions of the lightning strike, but I never expected NINE of them!

I am hoping that with this hint, I may get a few people using IT in a cleverer way to make genuinely new discoveries.

Anyhow, that's why it's been a while (there's also another rather different book in the works, but I'm not discussing that just yet—unless I mentioned sheep wearing Viking helmets so people will mistake them for mad cows and not eat them—shhhh!).  Next week, I'll get back to posting some off-cuts from Australian Backyard Naturalist.


* Wilson, or Bun-bo-e was a convict who, when his time expired, went to live among the Aborigines and became an initiated man. I am exploring his story at the moment as well.

Saturday, 2 June 2012

Thinking about slugs and snails

Rule 1 of being a naturalist: the most interesting questions are your own questions!

These are some random thoughts about snails that were left over from the book.  Waste not, want not!

Snail home.
Slug home.
I was inspired by the fact that I have had a snail living in a jar on my desk since the start of the year.

If you read my book, Australian Backyard Naturalist, you will learn that the shot on the left is of a slug that lived in that jar for ten months, given regular feeds of lettuce, spinach and bok choy, before I let it go. The photo on the right shows a snail with a damaged shell that has been living in the jar since the start of 2012.

I don't want to let it go, because, with a big panel of shell missing, it won't last long, so I am waiting to see if it can repair its shell.  I don't think it can.

You may like to try conducting some snail races.

You might like to try using light or dark to get snails to go in a single direction, or you might like to see if snails can be attracted by a favourite food—assuming you can identify the favourite foods of snails!

Some foods you might like to try: basil, lettuce, almost any young and tender seedling shoots. Try planting three or four types of seed in a single tray. After a week, when the seedlings are shooting nicely, add several snails, cover the tray, and then come back the next morning to see which seedlings were eaten first.

Be careful not to jump to conclusions until you have tested a few other possibilities!

I have a theory that some hairy or spiny leaves may be less attractive to snails and slugs. Can you test that?

Are snails faster than slugs?

Snails come out when it rains
This makes them excellent for rainy day investigations like these:

To observe snail movement, put a snail on a piece of flat glass, and hold it up to look from below.

To record snail trails, you will need a snail, a clean sheet of paper, and a supply of pepper. Put your snail in the middle of the paper, and leave it alone. After a while, the snail will start to travel across the paper. If there is a slime trail, sprinkle pepper on the trail before the slime goes hard.

Can you invent snail art?

How do snails react when they cross the slime trail of another snail? Does the age of the trail make any difference to the way they react?

How long does it take for a slime trail to go hard?

How many days does a trail last?

Where does it disappear to?

You may care to see whether you can get a slime trail like those of land snails from slugs and marine shellfish. I have never tried this: I predict that marine shellfish do not make a slime trail, but that slugs do. Perhaps you might like to work out why I think this, and then test it.

What use would a snail trail be to a predator? From this, can you make some predictions about the smell or taste of the slime trail? How would you test your predictions? Do so.
These shells were all attacked by predators that bored the shells.

You will need a large supply of bored shells of one species of seashell. Examine the shells to see whether the boring predators go for any particular part of the shell in a given prey species, or if they just bore at random. You will need to think about how you analyse your data.

As a follow-up, you may need to study the anatomy of the selected species to see what the borers aimed at. Some of the victims are bivalves, shellfish with two shells, which are more distantly related to the snails. Think about where the muscle is thet holds the shells together.

When a garden snail is threatened, it pulls back into its shell and often produces bubbles of mucus. My guess is that these bubbles taste bad or are poisonous, but I have never tried a taste test, and I don't recommend the experiment! Incidentally, snails are edible, but don't eat garden snails, in case one of your neighbours is using some sort of snail poison.

Just watching a snail move can be fun. This one is from the
Margaret River area, and I shot it in late afternoon sun.
Why do so few slugs get eaten? One way to find out might be to try eating a slug, but this is not a good idea. What if it has just eaten snail and slug poison or makes its own poisons (and how can you be sure?). What effects would these poisons have on the wildlife in your garden?

By the way, at least one sea slug, found on New Zealand beaches, carries a deadly poison, tetrodotoxin, but no Australian deadly sea slugs are known. Tetrodotoxin is the same poison found in the Japanese fugu fish and the deadly Australian blue-ringed octopus.

These land snails were all gathered on the Swan River at
North Fremantle.  Take a close look, and see how many
different species I found. I think there are three or four.
By the way, if you click on any picture, you see a larger form.
How does a snail's speed vary with size and weight? Does it go faster at a certain temperature or humidity?

Put ten snails in the middle of a black plastic sheet at night, and make a circle of bricks, with 5–10cm gaps between them, all round the snails. The next morning, check for trails and decide whether snails can see or not? Run the same test during daylight and compare the results. If you learn nothing, does that tell you something?

What senses do snails have? Do they react to sights, sounds, smells, or touch? How can you tell the difference between a snail reacting to the touch of a puff of air and a snail reacting to the smell carried in that puff of air?

If people worshipped the Giant African Land Snail, would this be an escargot cult?

Why don't people worship writers who make bad puns?