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Posts Tagged animal diversity

it’s the season for ‘best-of’ science compilations… Alison Campbell Dec 17

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… and so here are a couple of compilations.

The first is Sciencealert's top 10 animal videos for this year. They include a lone porcupine seeing off a pride of 17 (!) lions; an octopus 'walking' on land (which is really really strange: it must take an awful lot of effort to do this, unsupported by water, & to what end?); and – reminiscent of someone slurping down spaghetti – a giant red leech engulfing an even larger earthworm

Or, if 'cute' is your thing, then try the year's 'top 10 cutest animals in science' from the Washington Post. In a win for video instruction, it seems that marmosets can learn new tricks by watching the instructor on video. I must take a compass with me when walking the dog, so that next time nature calls I can see if he's lining himself up with the earth's magnetic field! But I think the little koala wins on the squee! factor :) (Image credit Reuters/Daniel Munoz)

from small beauties to a big one Alison Campbell Dec 07

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Is it a peacock? Is it a turkey?

Another in the occasional series of gorgeous creatures: the ocellated turkey :)

Image credit: backyardchickens.com

Over on Tetrapod Zoology, Darren Naish provides the detailed story of this species' biology & evolution.

Apparently they are difficult creatures to keep in captivity, so they won't be appearing on the Christmas menu any time soon. They're native to an area of about 130,000 square km across northern Belize, northern Guatemala, and the Yucatan peninsula.

When I first saw an image of this stunning bird (on FB, as one might expect) I thought I was looking at the male of a strongly dimorphic species. However, it turns out that both sexes share this spectacular colour pattern, although the colours may be somewhat muted in females. They're easier to distinguish in the breeding season, because the red & yellow lumps, or nodules, that dot the head & neck swell in males & become even more brightly coloured.

Sadly, as Matt Milner notes on the Cool Green Science blog

Most conservationists consider it near-threatened, with deforestation making the birds easier to kill by local subsistence hunters, a major factor in the species’ decline. 

The North American wild turkey got pushed close to the brink of extinction in New York state & has since bounced back due to careful management of the population and it's habitat, so there's hope for its gorgeous cousin if suitable conservation mechanisms can be identified & put in place.

 

rapid evolution in cane toads Alison Campbell Oct 27

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In her book Paleofantasy, Marlene Zuk discusses cane toads (Bufo marinus) as an example of just how rapidly evolutionary processes can work. These amphibian pests were introduced into Australia in 1935 to control borer beetles in sugar cane. Unfortunately the toads never got the memo about this expectation, and have spread rapidly across the continent, damaging a range of native ecosystems as they go. (They’re aided by the fact that they’re toxic, killing many of the predatory animals that might otherwise eat them.)

And it’s not just that the toads are and always have been fast hoppers. As this article says

When the toads were first introduced, they spread at a rate of about six miles (ten kilometers) per year. Today cane toads advance more than 31 miles (50 kilometers) annually.

In other words, they’re getting faster, with animals at the ‘invasion front’ moving up to 1.8km in a night. (The researchers were able to measure the toads’ speed by fitting them with miniature radiotransmitters, strapped to their waists.) Phillips & his colleagues (2006) point out that speed of movement in toads is correlated with leg length, and asked the question: is there a difference in average leg length between toads at the front of the amphibian wave spreading across Australia, and those at the back of the bunch? The answer:

As the toad invasion front passed our study site, we measured relative leg lengths of all toads encountered over a 10-month period. Longer-legged toads were the first to pass through, followed by shorter-legged conspecifics (order of arrival versus relative leg length: r = -0.34, n =552, P = 0.0001). Longer-legged toads therefore moved faster through the landscape.

And the evolutionary changes don’t stop there. In a paper just out, Brown, Phillips & Shine (2014) describe how the animals’ tendency to travel in a straight line has changed too:

Radio-tracking of field-collected toads at a single site showed that path straightness steadily decreased over the first 10 years post-invasion.

The research team found that this behavioural change had a genetic underpinning. The progeny of toads from the invasion front moved in straighter paths than the offspring of toads from older, well-established populations to the east. In addition, “offspring exhibited similar path straightness to their parents.” Brown & his colleagues concluded that

The dramatic acceleration of the cane toad invasion through tropical Australia has been driven, in part, by the evolution of a behavioural tendency towards dispersing in a straight line.

G.P.Brown, B.L.Phillips & R.Shine (2014) The straight and narrow path: the evolution of straight-line dispersal at a cane toad invasion front. Proc.R.Soc. B 281(1795) doi: 10.1098/rsph.2014.1385

B.L.Phillips, G.P.Brown, J.K.Webb & R.Shine (2006) Invasion and the evolution of speed in toads. Nature 439: 803. doi: 10.1038/439803a

Teachers: there’s an open-access summary of the 2006 paper here.

fluffy the dinosaur Alison Campbell Aug 11

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Over the last 20 years quite a bit of evidence has accumulated indicating that at least some dinosaurs were feathered, much of it in the form of beautiful fossils from China. Up until now all the feathery dinos have been members of the carnivorous theropods, but this new paper by Godefroit et al (2014) extends that fluffiness in its description of a herbivorous dinosaur, Kulindadromeus zabakialicus. (The full paper is behind a paywall but the BBC offers a good general summary.)

It’s now generally accepted that birds evolved from a theropod lineage (Michael Benton discusses the evolutionary changes that this entailed, here), although there is still debate around the origins of things like wings, feathers, and when birds/dinos first took to the air. Most people are probably familiar with at least the name of Archeopteryx, but since 1994 those Chinese fossils have shown us that many more theropods were feathered, and that feathers evolved well before the first bird-like creatures took to the air. Godefroit & his colleagues comment that

fully birdlike feathers orginated within Theropoda at least 50 million years before Archaeopteryx.

and there’s even discussion around whether the fearsome T.rex may have been feathery/fuzzy.

But Kulindadromeus wasn’t a theropod – it was a ‘neornithischian’ – an early member of the ‘bird-hipped’ dinosaurs, a group that includes Stegosaurus and Triceratops. (This nomenclature can get a bit confusing, especially when you consider that birds evolved from ‘saurischian‘, or ‘lizard-hipped’ dinos.) And while it didn’t have the sort of feathers that we’re familiar with today, it did have a range of other structures in addition to the usual scales:

monofilaments around the head and the thorax, and more complex featherlike structures around the humerus [upper forelimb], the femur [thigh], and the tibia [lower leg].

It’s early days yet. But if other ornithischians are found with  feathers, then then this would raise the possibility that the common ancestor of both dino groups also had some sort of feathery structures on its body, and would support the authors’ suggestion that

feathers may thus have been present in the earliest dinosaurs.

In other words, feathers may well be much, much older than we’ve thought.

 

P.Godefroit, S.M.Sinitsa, D.Dhouailly, Y.L.Bolotsky, A.V.Sizov, M.E.McNamaram M.J.Benton & P.Spagna (2014) A Jurassic ornithischian dinosaur from Siberia with both feathers and scales. Science 345: 451-455 . doi: 1126/science.1253351

one of the largest living insects? Alison Campbell Jul 23

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If you don’t like spiders then you probably wouldn’t like this either: from China come reports of what’s claimed to be the largest known aquatic insect. (I can’t find any actual published scientific descriptions of the creature; it will be nice to see the claim confirmed – or denied! – as it’s a pretty impressive specimen.

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My first thought on seeing this image was, a dobsonfly! I’ve not ever seen an adult specimen, but the aquatic larvae I encountered when running a macroinvertebrate lab class (way back in my Massey days) have equally impressive mandibles – hence the nickname of ‘toe biters’. Given that the adult Megalopteran pictured here has a 21cm wingspan (!), I wouldn’t care to encounter its larvae when paddling in a stream.

Becky Crew has a great take on this creature on her Running Ponies blog, including some fascinating info on other giants of the insect world.

if fish had nightmares, these spiders would feature in them Alison Campbell Jun 19

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If asked, “what do spiders eat?”, my answer would probably include insects, spiders, other arthropods, and maybe birds. I’d never have thought of fish!

And yet it seems that fish-eating by spiders is, if not common, then not exactly rare, although other food items still account for most of the spiders’ diets. In a paper just published in PLoS ONE, Nyffeler & Pusey (2014) present evidence – from an extensive literature review – for eight-legged piscivores on every continent other than Antarctica, although they’re more often found in tropical & sub-tropical regions. And it seems they’re not alone: the authors list a number of other arthropods with similar tastes, including water scorpions, backswimmers, caddis flies and water boatmen.

The spiders involved were mostly from the genera Dolomedes & Nilus ie they are large (as spiders go: a big female Dolomedes can have a leg-span of 6–9 cm and weigh ~0.5–2 g) and semi-aquatic, spending a lot of time at the water’s edge. Here’s an image of a female Dolomedes from the UK, settling in to consume a stickleback:

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Image: Nyffeler & Pusey (2014) doi:10.1371/journal.pone.0099459.g007

Incidentally, while we have spiders of this genus in New Zealand, it seems our small freshwater fish have little to worry about. Nyffeler & Pusey report that

only the largest of New Zealand’s three species of Dolomedes (Dolomedes dondalei) was capable of catching fish in laboratory experiments whereas the two smaller species (Dolomedes aquaticus and Dolomedes minor) were not.

When hunting fish – & for most spiders the researchers note that fish are a relatively rare component of the diet – the arachnids seem to use touch (mechanoreception) rather than vision. They sit at the water’s edge with their front pairs of legs spread out & resting on the water surface, and the others anchoring them to a rock or a plant. In some cases, especially when the water is calm, it seems that the spiders may detect their prey from ripples in the water, but in others their attack is triggered by the fish’s dorsal fin actually contacting one of their legs. And while spiders usually eat other animals smaller than themselves, in the case of fishing spiders their prey may be more than twice as large as the predator, which means that there’s quite a lot of effort involved in subduing dinner (usually done by biting the fish behind the head). and then dragging it out of the water to feed.

Nyffeler & Pusey cite experimental evidence showing that spider venom is quite capable of killing small fish, although it may take 20 minutes or more to do so. In the wild, that would be a long time to hang onto a wriggling fish. And why then drag it out of the water? Perhaps because the digestive enzymes injected into the prey would otherwise be diluted – remember that spiders are ‘liquid feeders’ who must wait until the prey’s innards have been liquified by those enzymes before slurping up the resultant soup.

While the fish these spiders eat are a large prey item, & capturing them must incur some risk, the researchers argue that such hunting may well be advantageous at times when other prey items are rare. However, they conclude that

Complete piscivory is probably rare and restricted to those occasions when semi-aquatic spiders gain easy access to small fish kept at high density in artificial rearing ponds or aquaria or in small shallow waterbodies.

Owners of home aquaria and fish ponds may never view Dolomedes in quite the same way again…

Nyffeler M, Pusey BJ (2014) Fish Predation by Semi-Aquatic Spiders: A Global Pattern. PLoS ONE 9(6): e99459. doi:10.1371/journal.pone.009945

a bunch of fascinating animals you’ve never heard of… Alison Campbell May 30

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… unless you’ve been following this blog for a while, in which case you may already have read about the sarcastic fringeheads (who are not members of a rock band, despite the wonderful name!).

The dumbo octopus, the pacu (a fish with teeth like nutcrackers, an attribute that has given rise to an urban myth guaranteed to alarm men), the pink fairy armadillo – yes, really! – visit the IFLS webpage and read all about them!

fascinating stories of dna, and the kiwi’s close cousin uncovered Alison Campbell May 28

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On Monday I was lucky enough to attend a lecture by Alan Cooper, director of the Australian Centre for Ancient DNA and one of the authors on a very recent paper that provides a new view of kiwi evolution (Mitchell et al., 2014). It was a fascinating & wide-ranging talk that started with a bit of a travelogue, as Cooper told his audience about some of the places he’s visited on his search for ancient DNA (aDNA).

To do their aDNA work, he & team use well-preserved organic material – usually found  in rather cold dry places. One of these was Mylodon Cave in Patagonia, named for the extinct ground sloth, Mylodon, whose remains littered the cave – in fact, much of the floor of the cave is apparently covered with balls of ground sloth dung! In the images we saw, much of the cave looked like a bomb site: it seems this impression was close to the mark as in the past local farmers had used dynamite to excavate fossils for sale to museums.

Cooper’s also worked – in the summer – in permafrost zones in northern Alaska looking for remains of mastodon & bison,  and finding mammoth bones along the way. (He didn’t sound very impressed about it!) Everything they found had to be carried down braided rivers by inflatable kayaks (which don’t have a good centre of gravity & makes travel a real challenge).

He’s certainly got some pretty wide-ranging research interests:

  • mammoth blood: looking at changes in their DNA that might be associated with haemoglobin function. With some mammoth tissue samples, a bit of genetic tweaking, and a vat full of bacteria the team were able to express mammoth haemoglobin & then look at its functioning. The oxygen-carrying protein turned out to be temperature-insensitive, releasing O2 at a steady rate regardless of temperature. This raises the possibility that in mammoths, their ears, legs & feet could cool right down without this drop in body temperature interfering with haemoglobin’s ability to deliver oxygen.
  • megafaunal ecology;
  • other extinct animals such as the thylacine, sabre tooth lion, dodo, and Falkland Islands wolf;
  • human evolution, including examining the remains of our own relatives: Neandertals and Homo floresiensis (aka the ‘hobbits’ – in the talk, he suggested this species may have become extinct closer to 50,000 years ago rather than the original date of around 13,000 years before present.)
  • South American mummies, gaining information on human migrations & cultural changes.
  • animal domestication – including using data from animal remains as a proxy for patterns of human migration & cultural change.
  • evolution of disease – eg calcified bacteria, or dental calculus, on human teeth (including on australopiths) gives a record of all bacteria in an individual’s mouth & allows us to track the human microbiome through time.
  • palaeoenvironments and metagenomics: using information from things like stalactites, sediments, and coprolites (fossil dung eg from moa) to reconstruct ancient ecosystems.

With any work involving DNA, researchers have to avoid contamination of their samples from other sources of DNA (including themselves). When it’s aDNA the problem is magnified enormously, because the initial samples are so small that the ancient signals would be swamped in the ‘noise’ of modern contaminants. This meant that the research team have to do all this work away from any labs regularly working with cloning and PCR, and so they work in purpose-built lab facilities, away from the main university campus. Positive air flow in the labs prevents dust etc entering. Staff can’t bring anything in that’s been at the university and must don gowns, masks & hoods with even more care than a surgeon (at this point I couldn’t help feeling that the folks working there would need excellent bladder control, since gowning is a lengthy process & one must perforce leave the lab & ungown in order to seek a little excretory relief). Any goods coming in are ‘fried’ by a UV oven. The rooms where the actual research is done are ‘still-air labs’ within the positive pressure environment: people must move around rather slowly to minimise the creation of air currents that would spread aerosol droplets with potential to contaminate between samples. This must be a cause of some perplexity &/or amusement to those able to view the scientists from the gardens outside :)

Then we moved on to the ratite birds, or palaeognaths: the latter name refers to the structure of their palate, a feature that unites the tinamou, ostrich, rhea, cassowary, emu, and kiwi, along with extinct species such as moa and elephant birds. This means that there are extinct & living ratite species on all the southern continents (apart from Antarctica – but then they would be rather hard to find there given its present ice-covered state). The tinamou is unusual – it’s the only living ratite that can fly.

Early ideas about ratite evolution cast them as ‘primitive’ species that only survive on the Gondwanan land masses because they’d been outcompeted everywhere else, and with their flightlessness as an ancient characteristic. (The tinamou, of course, was something of a feather in the ointment for this viewpoint.) Ratites became poster chicks for continental drift, because the data then available suggested that ratite adaptive radiation seemed to fit with the sequence of continental movement: Africa was the first continent to separate and ostriches were the ‘oldest’ of the birds.

Alan Cooper has had an interest in this story for a long time: he began his research career working on moa remains, aiming to extract & amplify mtDNA from mitochondria. (This is much easier to get than nuclear DNA (nDNA). It’s also inherited down the maternal line, and he characterised it as usually neutral with respect to the overall evolution of a group of species.) Eventually he sequenced the entire mtDNA genome of two moa, and also got fragments of the genome from Madagascar’s extinct elephant bird. At the same time he found that the kiwi was more closely related to cassowary & emu than to the moa, & his fragmentary data for the elephant bird also suggested that it was relatively closely related to kiw. How could this be?

Then in 2010 new research using nDNA found that tinamous were not the ‘outgroup’ for ratites (ie only distantly related to the rest of the species in this group), but were instead most closely related to moa (Phillips et al., 2010). Not only did this study place ostriches as the outgroup for the ratites; it also concluded that flightless had been lost independently in the various species – it was not an ancestral feature. This suggested that the various ratites must have dispersed by flying, & subsequently lost that ability.

This research didn’t include elephant birds, for which there are very few skeletal remains. Most authors think there were around 7 species, but Cooper suspects they are not taking into account sexual dimorphism. This has been well documented in moa, where females are much larger than the males (a realisation that saw a reduction in the number of moa species we recognise). And large elephant birds weighed around 275kg – about 40kg heavier than the largest moa. Cooper says he spent ages looking for remains that were likely to yield DNA, eventually going back to the specimens from Te Papa that he’d used in his original research. His research team designed suitable molecular probes – short sequences of DNA based on the mtDNA of modern ratites. They also obtained a ‘library’ of all the elephant bird DNA that they could sequence, recognising that this probably also contained contaminants from various microbes. The probes and the elephant bird sequences were mixed, which allowed the probes to ‘hybridise’ wherever their sequences matched those from the birds. The hybrid mtDNA could then be pulled from the mix, thus leaving behind DNA from bacterial & fungal contamination. The result of all this was a very good coverage of elephant bird mtDNA (apparently as good as what is returned from work on modern human DNA).

These sequences were then compared to data from all other living ratites. The results identified elephant birds as the closest relatives of kiwi: they are sister taxa. The data also confirmed the moa-tinamou grouping, again placed ostriches as the outgroup for ratites, and gave relatively recent divergence dates for the various ratites that don’t match the timing for the break-up of Gondwanaland; ie the order in which the Gondwanan continents separated has nothing to do with ratite distribution. Also, the additional support for the moa-tinamous sister relationship reinforces the idea that ratites were originally flighted. Cooper suggests that flying ratites were spreading around the continents following the end-Cretaceous mass extinction event that saw off the dinosaurs (and many other groups besides), and subsequently – in the absence of large mammalian predators and competitors – converged on the giant flightless form, filling the ‘large herbivore’ niches left vacant by the dinosaurs. (The subsequent adaptive radiation of large mammals prevented the more recent ‘neognath’ birds from also following this path.) In other words, it’s highly likely that the ancestors of both kiwi and elephant bird came from ‘somewhere else’, most likely Antarctica.

The talk finished with a possible answer to the question: why is the kiwi so small, & its egg so large? The genetic data indicate that the ancestors of modern kiwi arrived in New Zealand well after the moa had expanded into the large-herbivore niche, and took on the role of a nocturnal insectivore. Similarly, tinamous arrived in South America well after the rheas had evolved. With no mammalian predators, kiwi lost the ability to fly – unlike the tinamou, in a land with a variety of mammals present. And the egg? Stephen Jay Gould suggested that kiwi had shrunk but that there was some selective advantage in retaining large egg. Cooper’s explanation proposes that with a number of large avian predators around (eg Haast’s eagle, laughing owl), newly-hatched ground-living kiwi chicks would be in some danger of becoming a meal. He feels that the adaptive significance of the unusually large egg is that it allows a kiwi chick to stay in the burrow for at least a week after hatching, so when it leaves the burrow’s protection it’s already very active and perhaps better able to avoid predation.

It was a fascinating tale, well told.

 

K.J.Mitchell, B.Llamas, J.Soubrier, N.J.Rawlence, T.H.Worthy, J.Wood, M.S.Y.Lee & A.Cooper (2014) Ancient DNA reveals elephant birds and kiwi are sister taxa and clarifies ratite bird evolution. Science 344 (6186): 898-900. 10.1126/science.1251981

M.J.Phillips, G.C.Gibb, E.A.Crimp & D.Penny (2010) Tinamous and moa flock together: mitochondrial genome sequence analysis reveals independent losses of flight among ratites. Systematic Biology 59(1): 90-97. doi: 10.1093/sysbio/syp079

something reassuringly disgusting… Alison Campbell May 04

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This post's title comes from Something Fishy where, talking about sea cucumbers, Illya wrote "But there's something else they can do. Something reassuringly disgusting. Something totally Sea Cucumber." I was mildly let down to find he was talking about bioluminescence, & not self-evisceration.

Yes, that's right. When threatened (or repeatedly prodded by some uncouth human in a wetsuit), some types of sea cucumber can forcibly expel part of their gut (& other organs) through the body wall – not the cloaca, but various points on the body wall. I knew that the self-evisceration happened, but not how it happened. For that, I went to the most excellent echinoblog, and you should too, for not only is there an excellent explanation but there are pictures

And so I have learned that holothurians have got this really weird connective tissue that they can soften very quickly indeed, so that the gut's normal connections to other internal bits & pieces is weakened, fast. At the same time regions of the body wall also weaken, and then strong muscle contractions expel parts of the body that would normally never see the light. 

The adaptive significance of all this? (You might regard the practice as a fast track to evolutionary oblivion, but these extraordinary animals are able to regenerate the missing bits.) The 'standard' explanation has been that it's a defence against predators, but echinoblog offers another option: that it's a means of getting rid of excretory byproducts that would otherwise build up to harmful levels in the body. This is borne out by the observation that some sea cucumbers expel their innards – & regenerate them – on an annual basis.

There's the potential to learn a lot from these unusual creatures.

 

another see-through animal (& a rather lovely image) Alison Campbell May 02

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I saw this little critter a while back, over on Pharyngula, & put it on the list of Things To Blog About. Somehow, it took me a while to actually get onto it, but we've got there in the end :)

Image credit: Laurence Madin, Woods Hole Oceanographic Institution/CMarZ, Census of Marine Life

I was a bit puzzled when first I saw this picture – the animal has a vague flavour of jellyfish to it, but I knew it couldn't be one due to its tubular gut. (Jellyfish and their relatives have a sac-like gastrovascular cavity, where a single opening serves as both mouth and anus). So I read on, and found out that it's actually a sea cucumber, in the same phylum as starfish, sea urchins, brittle stars, and the less-familiar feather stars and sea lilies.  It belongs to the genus Enypniastes, but has been dubbed the 'headless chicken fish' in this most entertaining blog over at Something Fishy.

I was surprised to find that Enypniastes is able to swim (although apparently this behaviour isn't all that unusual), something it does v-e-r-y s-l-o-w-l-y using the cape of tentacles at its anterior end. It feeds on detritus in the deep ocean, and like all sea cucumbers, the contents of its digestive tract exit the body through a cloaca, a 'multipurpose' structure. In the case of the holothuroids, this multipurposing includes gas exchange, using complex 'respiratory trees branching off from the cloaca. A while back I wrote more about these structures, which may also serve as both anti-predator devices and homes for small fish…

I think perhaps I should add the see-through Enypniastes to the list of creatures for my next talk on the weird and the wonderful :)

 

 

 

 

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