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Posts Tagged animal diversity

‘slow life’ – corals and anemones strut their stuff Alison Campbell Mar 29

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When I was a kid we used to go to the beaches of the Mahia peninsula most weekends. (Well, memory says 'most weekends' – it might not have been that often!). Sometimes we'd stop at the sweeping sandy shores of Blue Bay, but on other days we'd go round to the exposed rocky coast & spend happy hours messing around in the rock pools. I used to love floating my fingers past the sea anemones & feeling the tiny tugs as we touched (at the time, of course, I had no idea that those tiny tugs were the anemones discharging nematocysts into my fingers!) And to me it seemed that these intriguing little animals, which retracted into blobs of jelly when touched less gently, didn't really seem to do much.

Similarly corals – when we've snorkelled around corals I've been amazed by the forms they take and – in living corals – by their colours. But it's hard to see much actually happening.

But tonight a friend of mine posted this video – "Slow Life" – on their Facebook page. It's gorgeous, visually stunning – and it shows the hidden life of cnidarians in glorious technicolour. Best on the big screen, I think; I'm looking forward to showing it to my first-year class next week.

Enjoy!

just like ‘alien’ – moray eels have *two* sets of jaws Alison Campbell Dec 19

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Around 14 months ago the husband & I were spending a lazy holiday in Rarotonga. We did quite a bit of snorkelling on the reefs, and especially enjoyed our experiences at Muri, where we saw a good range of reef fish in near-ideal conditions (as in, clear, calm, relatively shallow water). There were several moray eels, which were at first hard to spot – and then you saw them, loitering in a crevice, giving the impression of watching you rather closely and with their open mouths exposing some rather sharp, pointy teeth: “all the better to bite you with, my dears.” We viewed them with caution.

But when you think about it, that wide-mouthed loitering would seem to pose a problem for the eels. This is because most predatory fish feed by opening their mouths wide from a closed position: water floods into the lower-pressure area inside the mouth & dinner comes along for the ride. Sitting around with your mouth half-open doesn’t sound like a good strategy. I found the answer while reading The Book of Barely Imagined Beings by Caspar Henderson, under – you’ve guessed it – ‘E for Eel’. (This wonderful book was recently reviewed on Sciblogs by Siouxsie Wiles.)

 

As an aside, I love the way this chapter kicks off:

The Snowflake1 eel, a kind of moray, is harmless if you leave it alone and refrain from drinking its blood (which is toxic).

I was also fascinated to know that the morays’ genus, Echidna, derives from a rather unpleasant individual in Greek mythology; beside her, Henderson says, “the Snowflake and other Moray eels are pussycats” – yet people still fear them:

Part of the reason for this is surely their superficial resemblance to snakes… Another may be the eels’ mouths, which are constantly open, suggesting that they are ready to strike. But this is not, I think, the whole story. An eel’s eyes, bulging and unblinking, look like those of a corpse, and the way the animal moves its body … is disturbingly sensual. Saltwater eels are uncanny.

You can see, I hope, why I like the book; the writing is lovely. But anyway, back to those gaping maws.

Henderson explains how a moray’s hunting style more closely resembles the eponymous ‘Alien’, for these eels have two sets of jaws! The second set is found in the back of the throat – the ‘pharyngeal jaws’ -  but can be thrust forward extremely quickly and retracted equally rapidly, so that they “[pull] the prey down into the oesophagus as the animal closes its mouth.” You can see how this all works in the image below, from the National Science Foundation website.

Image credit: Zina Deretsky, National Science Foundation (after Rita Mehta, UC Davis)

The work of Rita Mehta, who’s been studying moray eels’ feeding anatomy, is featured in the following video, in which you can see those pharyngeal jaws move forward to grasp a ‘prey’ item. All the more reason to be fairly circumspect on the reef, methinks!

1 If you think ‘Snowflake’ is an unusual name for an eel, how about the ‘Rusty spaghetti’ version?

kiwi evolution – a new take on an icon’s ancient past Alison Campbell Dec 18

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‘The’ kiwi (Apteryx spp.) has always been a bit of an enigma, not least for the fact that it lays an absolutely enormous egg in comparison to its body size. In one of the essays in his book Bully for Brontosaurus (1991), Stephen Jay Gould argued that this differential in egg/body size was due to the impact of scaling: kiwi, he believed, had ‘downsized’ from a moa-like ancestor but had retained the large moa-type egg. This idea was quite widely accepted, even though later genetic evidence indicated that kiwi were in fact more closely related to the Australian emu than to NZ’s now-extinct moa. But new research suggests quite a different evolutionary trajectory – and I rather suspect that Gould, great scientist that he was, would be delighted to see his hypothesis robustly challenged :)

The research reported in this news article from scoop.co.nz will be published in the Proceedings of the 8th International meeting of the Society of Avian Palaeontology and Evolution – you’ll find the abstracts of the conference papers here. A newly-described fossil, from what’s known as the ‘St Bathans fauna’ of Central Otago turns out to be a new genus and species of kiwi, but a tiny one by today’s standards. Paul Scofield, one of the paper’s authors, is quoted in the scoop report as saying that

[this] fossil from the early Miocene, about 20 million years ago, shows us that it’s a tiny bird about one third the size of a small kiwi today. It suggests the opposite [to Gould's hypothesis] is, in fact, the case – that the kiwi has developed towards a larger size, a trend that is seen in many birds from the early Miocene.

So, how would an ancestral kiwi have arrived in New Zealand? The suggestion is that they flew. This is based on the evidence that a) kiwi and emu are more closely related than kiwi and moa and b) the emu-ish early kiwi arrived here after NZ and Australia were separated by the developing Tasman Sea.

Finding the wing bones of this new fossil species would help to confirm/deny this proposal. Although – having read the abstracts for the conference, I can’t help wondering if a proxy might be the size of a part of the brain known as the ‘cerebellar flocculus’, as suggested in another presentation by Walsh et al. It’s an intriguing possibility, anyway! And I’m wondering – how may we then explain that anomalous kiwi egg?

I’ll look forward to getting hold of a copy of the paper by Worthy and his colleagues, once it’s published.

 

Gould, S.J., (1991) Of kiwi eggs and the Liberty Bell, pp 109-123 in Bully for Brontosaurus. Penguin Books, London. 

Walsh, S., Iwaniuk, A., Knoll, M., Bourdon, E., Barrett, P., Milner, A., Abel, R., & Dello Sterpaio, P. (2012) Can the size of the avian cerebellar flocculus be used as a proxy of flying ability in extinct birds? 8th Internat. SAPE Meeting, 11.-16. June 2012 Naturhistorisches Museum Wien

Worthy, T.H., Tennyson, A.J.D., Salisbury, S., Hand, S.J., & Scofield, R.P. (2012) A fossil kiwi (Apterygiformes) from the early Miocene St Bathans fauna, New Zealand. 8th Internat. SAPE Meeting, 11.-16. June 2012 Naturhistorisches Museum Wien

a glorious (but deadly) cephalopod Alison Campbell Nov 18

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Every now & then the husband goes on a fossil-fossicking expedition, in order to add to his collection of things long dead & turned to stone. There are a number of good sites in the Waikato region, and one of them has yielded quite a few belemnite remains: specifically, the bullet-shaped fossilised internal shells of one group of cephalopods. Plus he’s also found a few rather lovely ammonites, though nothing on the same scale as a giant specimen found near Kawhia Harbour in 1977. (Apparently the largest of all was found in Germany – its shell, if uncoiled, would be close to 11m long!).

The evolutionary history of cephalopods spans around 500 million years, and there’s a good overview of this on the UCMP(Berkeley) evolution website. I hadn’t visited this part of their site before, but was directed there by PZ Myers (who else?) & his use of this stunning image – too beautiful not to share :)

Beautiful, but deadly:

These little molluscs – members of the largest species grow to be about 15 cm long, head tip to tentacle tip – produce two different venoms. One, they use in hunting their usual prey1 of crabs and shrimps; the other is released when the animals are alarmed or agitated. While people certainly report blue-ringed octopus bites, it seems that the toxin may also be secreted directly into the water: the author of this website reports feeling localised neurological symptoms after putting his hand into a tank of seawater that had been used to transport a largish specimen. The venom contains the poison tetrodotoxin (TTH)2, also produced by a range of other organisms including a genus of newts, some harlequin frogs, snails, and worms from a number of different phyla. And, of course, the pufferfish, whose family name (Tetraodontidae) gives us the name of the toxin.

This poses an interesting question: why would members of so many different phyla evolve the same poison? It turns out that it’s not actually the animals who make the TTH: the job’s done by colonies of symbiotic bacteria living in their poison glands. Life really is more complex and more complicated than we can imagine.

1  Sometimes, the prey fights back:

2 It’s been suggested that TTH is the mysterious ingredient supposedly used in zombifying people – you’ll find an interesting discussion of this idea here on HowStuffWorks.

swimming as a sperm does Alison Campbell Nov 13

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It’s much harder for a sperm to swim, than it is for a sperm whale. Why? This excellent TEDed video explains:

I think I’ll use it next year, during the ‘reproduction’ section of my first-year biology paper :)

a creeping assassin Alison Campbell Nov 04

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The daughter & her friends play Assassin’s Creed from time to time. This little arachnid would fit right in:

Photo: Jeremy Miller

For this is an assassin spider, one of a number of species (in the superfamily Palpiamanoidea) that prey on other spiders.

The assassin spiders have a long history: a combination of fossil & DNA evidence suggests that they go to before the supercontinent Gondwana began to break up under the slow but irresistable influence of plate tectonics. While there’s one fossil found in what’s now the northern hemisphere, all living species are found south of the equator, in Madagascar, South Africa, and Australia.

These strange little creatures are only a couple of millimetres long, but have a set of adaptations that allow them to strike their prey from a (reasonably!) safe distance. Their fang-tipped jaws are enormous – in the image above, the jaws holding the spider’s meal are about the length of the animal’s abdomen. The long ‘neck’ is an extension of the cephalothorax – the first of the 2 major sections of a spider’s body (the other is the abdomen, or opisthoma). The combination of neck & jaws means an assassin spider can impale another spider before the latter is within range to strike back. That’s after they’ve found their prospective dinner by following lines of thread it’s left behind, using their very long forelegs (which may also be used to lure the prey closer.

Which is probably quite enough for those of you who aren’t fond of spiders, not even itsy little 2mm-long spiders. But for those who want to find out more, try this video:

essays on our fascination with those who are different Alison Campbell Oct 08

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Book Review: The Two-Headed Boy and Other Medical Marvels 

by Jan Bondeson

Cornell University Press, USA (2004)

Paperback: i-xxii, 297 pages

ISBN: 0-8014-8958-X

RRP: US419.95

It's all Grant's doing, really. If he hadn't picked up on an off-hand comment of mine (relating to vipers in bosoms) & turned that into a catchy blog post, I quite probably wouldn't have gone looking for other books by Jan Bondeson, or found The Two-Headed Boy and Other Medical Marvels

This is a fascinating, saddening, and occasionally appalling book by a humane and extremely well-read author. The subjects of Bondeson's essays are those who are (or were, for these are historical essays) in someway very very different from the rest of us: the exceptionally tall, the enormously obese, the unnaturally hairy, the two-headed boys of the title. Those who in what we'd like to regard as a less-enlightened age would have spent their lives in what were then called 'freak' shows, for others to gawk and gape at. (Not that this horrified fascination with those who are different has disappeared. We just don't deem it appropriate to pay to indulge it.) And while the money may have poured in from the gawkers, all too often most of it made its ways into the pockets of 'managers', and not the afflicted individuals. (Although there were exceptions, which we'll come to shortly.)

One of the things I particularly enjoyed about the book was its interweaving of scientific and historical perspectives. Did Countess Margaret of Henneberg really have 364 – or was it 365 – children all at once? Today we'd immediately say, well of course not! But then, what are the origins of the tale described in Bondeson's essay, "The strangest miracle in the world"? The author examines the development of the legend over the years, noting with wry amusement that until quite recently childless women would wash their hands in the bowl in which the unlikely children were supposedly baptised – even though the original was destroyed long ago. And he shows how science has a part to play in the explanation: it's possible that the Countess delivered a hydatidiform mole. Although you'd think that the midwives might have had some experience of this condition, the mass of small blobby bits might have been seen by them as a large number of gravely undersized babies.

At least Countess Margaret wasn't displayed for money (although the local townsfolk must subsequently have made quite a lot out of tourists), but money's involved in most of the stories. (And attention, which may well have been the driver for the poor lady who pretended to lay eggs – a tale which also attests to the extreme gullibility of those in attendance at the delivery!) Both Daniel Lambert (for a time the fattest-known human, although more recently he has been outweighed by a man nearly double Lambert's 700+ pounds) and the 'Swedish Giant', Daniel Cajanus, parlayed their physical extremes into quite comfortable livings, for not only were they charming and intelligent men but they also had the sense to manage their own affairs. All too often that hasn't been the case, with children put on display out of desperation or greed on the part of parents or 'managers'.

Of those children, I sometimes wonder if our most awful fascincation might not rest on conjoined twins. Bondeson discusses several examples, including parasitic twins and two-headed children. Apparently dicephalus (two-headed) twins represent around 11% of conjoined twins, the great majority of whom die before or soon after birth; certainly a google search will produce more images than you may be comfortable with. I first heard of them when reading Stephen Jay Gould's essay on the twins Ritta-Christina, in which he not only discussed the children's short, sad lives but also the issue of what constitutes an individual. Bondeson also tells their story, but the two-headed boys of his title had a better time of it; in fact, he describes Giovanni and Giacomo Tocci as the "most celebrated pair of dicephalus conjoined twins of all times". While most dicephalus twins are short-lived, often due to other structural abnormalities in one twin or the other, the Tocci brothers were born in 1877 and lived at least into the second decade of the 20th century, at least in part because the boys were 'symmetrical' in that both seemed to have properly-developed hearts and lungs. Like all the dicephalus twins described in the book, the Toccis were two distinct individuals with different personalities and intellects.

And this, of course, poses some serious ethical questions. While it is possible to separate some conjoined twins, depending on the degree to which they share organs and blood vessels, to do this for dicephalus twins means that either both would spend the rest of their lives incapable of independent movement & with significant post-surgical disfigurement, or one would be sacrificed that the other might live. To whom should this decision fall? (The parents of perhaps the most famous living dicephalus twins, Abigail & Brittany Hensel, never considered this option, & their daughters are now young adults.) 

Yes, this is a fascinating and thought-provoking book, not least because it offers a discomforting mirror in which to review how we see those who are so different from ourselves.

 

a beautiful nightmare Alison Campbell Sep 10

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A few weeks back I briefly mentioned the ‘bobbit worm’ – a rather large polychaete worm of scary appearance (a friend said ‘nightmarish’ was closer to the mark) and predatory habits. I’ve noticed on Facebook how interest in any particular subject seems to come in waves, and so it is with this creature.

For via FB I’ve come to Matt Simon’s interesting article – with Jenny Huang’s rather lovely photo – on wiredscience.

File:Eunice aphroditois.jpg

Image by Jenny Huang,via Wikimedia

A beautiful nightmare, then.

Apparently there’s not a lot known about them in the wild, but these worms can be a right pain in the proverbial for aquarium keepers: bring in some coral for your tropical marine tank, & it’s possible there’s a little bobbit worm hiding in there, ready to come out & pick off your fish when it’s feeling peckish. And growing bigger… up to 3 metres or more in length.

It’s possible that, like other similar polychaetes, bobbit worms reproduce in a distinctly odd manner: at certain times of year the rear part of each worms body, packed with gametes, breaks off and swims upwards to the surface in a massive, mass mating swarm. Which leaves Simon with the opportunity for a truly excellent punch-line for his story:

Hate to leave you with the image of a beautiful tropical ocean swarming with sex-crazed 10-foot-long worms with hair-trigger jaws, but that’s totally happening now.

a really strange sea urchin Alison Campbell Sep 01

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I mean, look at those really weird spines!

Image from Moorea Biocode via ScienceAlert

This unusual creature is Chondrocidaris brevispina, which appears to be much less spiny than the urchins we’re probably all more familiar with. Those pinkish pimply bumps towards the creature’s right-hand side are the bases of missing spines, which articulate with their bumps via a type of ball joint.

As the name ‘brevispina’ suggests, the spines are quite short. Those pink swellings on the end of each are apparently sponges, which leads me to wonder what restricts the sponges’ downward spread along each spine. Their lower limit seems very well defined. If this was a ‘normal’ urchin I’d wonder if that was due to the action of the structures known as pedicellariae, which are capable of nipping & crushing (& are sometimes venomous as well) – they’d certainly take care of an overgrowth of sponge!

Alas! Information on C.brevispina seems fairly scanty - a pity as I really would like to know more about those spines. Hopefully someone more learned in this area than I am can help me out :)

is this a coat of many colours? Alison Campbell Aug 21

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I had to look twice at this undersea Liberace-lookalike before recognising it as an octopus (more precisely, a blanket octopus, Tremoctopus sp.) These beautiful creatures live in the open ocean where they grow up to 2m long. The female in this image (thanks, Science Alert) has unfurled a sort of cape (called a ‘web’ in this Scientific American article) that may function in deterring potential predators – after all, you’d have to be fairly big to take on something of this apparent size. The web can be shed in sections, presumably acting as a distractor if the octopus is threatened by something large & hungry.

Interestingly, it’s only the females who can put on this impressive display (the cape’s rolled up when not in use), for the males are much smaller.  So small, in fact, that it was some time before one of the 2.4cm males was even identified. That’s a pretty extreme example of sexual dimorphism; in terms of the orders of magnitude between the size of the two sexes it must give some of the deep-sea angler fish a run for their money.

But also – it seems that small blanket octopuses (ie males & young females) use tentacles from Portuguese man-o-war jellyfish as defensive/offensive weapons, something that was first reported on back in 1963 (there’s an image here on the ToLWeb site). Presumably these cephalopods are immune to the jellyfishes’ stings.

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