Cuttlefish tailor their defences to their predators

Blogging on Peer-Reviewed ResearchThe best communicators know to cater to their audiences, and cuttlefish are no different. A new study shows that these intelligent invertebrates can target their defensive signals to the hunting styles of different predators.

CuttlefishCuttlefish and their relatives, the octopuses and squid, are expert communicators whose incredible skins can produce a massive range of colours and patterns. Cuttlefish mostly use these abilities to blend into the background but they can also startle and intimidate predators by rapidly changing the display on their dynamic skins.

Keri Langridge and colleagues from the University of Sussex, watched young cuttlefish as they were threatened by three very different predators – juvenile seabass, dogfish (a type of shark) and crabs. A glass partition protected the cuttlefish from any actual harm but gave them full view of the incoming threats.

She found that the cuttlefish only ever used startling visual displays when they were faced by seabass, which hunt by sight. As the fish approached, the young cuttlefish suddenly flattened their bodies to make themselves look bigger and flashed two dark eye-spots on their backs to startle the predator. This pattern is called a ‘deimatic display’ and it was used in 92% of encounters with seabass.

There’s a video of the deimatic display after the jump…

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Chimps trump university students at memory task

Blogging on Peer-Reviewed ResearchWe humans aren’t used to having our intelligence challenged. Among the animal kingdom, we hold no records for speed, strength or size but our vaunted mental abilities are unparalleled. That is, until now. New research from Kyoto University shows that some chimps have a photographic memory that puts humans to shame.

Chimps trump university students at memory taskSana Inoue and Tetsuro Matsuzawa have found that young chimps have an ability to memorise details of complex images that is literally super-human. Boffin chimp Ayumu, outperformed university students in memory tasks where they had to rapidly memorise numbers scattered on a touchscreen and press them in numerical order.

This is the first time that an animal has outmatched humans in a mental skill. Recently, I’ve previously blogged about animals that show abilities once considered to be uniquely human, including jays that can plan for the future, rats that know how much they know, cultured chimps, tool-combining crows, and discriminating elephants.

But in all these cases, the animals merely showed that they could do similar types of mental feats to us. They never challenging our abilities in terms of complexity or scale. Simply put, a crow may be able to combine tools together, but it’s never going to be able to engineer a computer.

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Envious capuchin monkeys react badly to raw deals

Blogging on Peer-Reviewed ResearchIn my last post, I wrote about two studies which showed that even bacteria cooperate towards a common goal and can be infiltrated by cheating slackers. In one of the studies, cheaters were eventually weeded out through natural selection because their rise to prominence created such havoc for the group that each individual bacterium suffered.

Envious capuchin monkeys react badly to raw dealsIn this scenario, slacking wasn’t punished but merely reduced over time. But more complex creatures, like humans, have the capacity to actually recognise unfairness and punish it directly. It turns out that we’re very keen on doing that; so strong is our innate sense of justice that we’ll often punish cheaters at our own expense.

Two years ago, Sarah Brosnan and Frans de Waal at the Yerkes National Primate Research Center found that brown capuchin monkeys also react badly to receiving raw deals. Forget bananas – capuchins love the taste of grapes and far prefer them over cucumber. If monkeys were rewarded for completing a task with cucumber while their peers were given succulent grapes, they were more likely to shun both task and reward.

That suggested that the ability to compare own efforts and rewards with those of our peers evolved much earlier in our history than we previously thought. Of course, animal behaviour researchers always need to be careful that they’re not reading too much into the actions of the animals they study.

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Elephants smell the difference between human ethnic groups

It’s tempting to think that elephants have their own PR agency. Just last week, their mighty reputation was damaged by the revelation that they are scared away by bees but they have bounced back with a new study that cements their standing among the most intelligent of animals.

A wary elephant catches the scent of MassaiLucy Bates and colleagues from the University of St Andrews have found that African elephants (Loxodonta africana) can tell the difference between different human ethnic groups by smell alone. They also react appropriately to the level of threat they pose.

The Massai, for example, are a group of cattle-herders, whose young men sometimes prove themselves by spearing elephants. Clearly, it would pay to be able to sort out these humans from those who post little threat, like the Kamba.

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Clever New Caledonian crows use one tool to acquire another

You don’t have to be particularly intelligent to use tools – many animals do so, including some insects. But it takes a uniquely intelligent animal to be able to combine different tools to solve a problem. We can do it, the great apes can do it, and now the New Caledonian crow joins our exclusive club.

New Caledonian crows are very advanced tool users.Animals can use tools using little more than pre-programmed behaviour patterns that require little intelligence. But combining tools, or using one tool on another (a metatool, if you will), is a different matter entirely – that takes reasoning.

This type of intelligence has been the engine of human innovation. It allowed us to use simple tools to make advanced ones, or to combine different tools into increasingly complex machines.

The majority of animals lack the ability to manipulate tools in this way and in primates, the line is drawn at the great apes – they can (mostly) do it, but monkeys struggle. So it may come as a surprise that a humble bird has now been found to use metatools to the same standard as our ape cousins – the New Caledonian crow.

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Simple sponges provide clues to origin of nervous system

The possible origins of the nervous system have been found in the simple sponge, an animal with no nervous system of its own. Sponges carry the genetic components of synapses, which may have been co-opted by evolution as a starting point for proper nerve cells

Sponges are the most primitive of all animals. They are immobile, and live by filtering detritus from the water. They have no brains or, for that matter, any organs, tissues or nervous system of any sort. If you were looking for the evolutionary origins of animal intelligence, you couldn’t really pick a less likely subject to study.

Over time, evolution co-opted the early PSD of the sponge and used it to craft true nervous systems.So it was with great surprise that Onur Sakarya from the University of California, Santa Barbara found that sponges carry the beginnings of a nervous system.

With no neurons to speak of, these animals still have the genetic components of synapses, one of the most crucial parts of the nervous system. And their versions share startling similarities with those of humans.

Synapses (and proto-synapses)

Synapses are junctions between two nerve cells that are allow the cells to pass on signals to each other. Signals are carried by molecules that cross the synaptic gap called neurotransmitters. When they reach the receiving cell, they come across an elaborate tangle of proteins called the post-synaptic density (PSD; labelled in red below). The PSD processes the neurotransmitters, among many other important roles, and allows the receiving cell to respond appropriately to the nervous signal

Sakarya searched for equivalents of the human PSD proteins in the genomes of other animals. For a start, he found an almost complete set in the starlet sea anemone (Nematostella vectensis). The anemone (like its cousins, the jellyfish) is one of the Cnidarians, a group of animals that have the most rudimentary of nervous systems. Finding PSD genes in them is surprising but reasonable.

The synapse relays signals from one cell to another.But Sakarya was really surprised when he found the vast majority of the PSD assemblage in the sponge Amphimedon queenslandica, an animal that doesn’t even have a nervous system! The sponge’s PSD proteins bore remarkable resemblances to those of humans and other animals, and were built of similar arrangements of domains.

One in particular, the PDZ domain, allows PSD proteins to recognise one another and assemble correctly. When Sakarya compared the structures of the human and sponge PDZ domains, he found that at the atomic level, the parts they used to interact with other proteins were almost 90% identical. So not only does the sponge have the full set of PSD parts, it can assemble them into a fully-functioning whole.


So what is the PSD, part of the nervous system, doing in an animal without one? Sakarya believes that the PSD is an example of exaptation, a process where evolution co-opts an existing structure for another purpose. Bird feathers are a good example of this – they evolved in small dinosaurs to help them regulate their body temperature, and were only later used for flight.

Exaptation can explain how complex, integrated structures like the nervous system can evolve. Rather than building the whole thing from scratch, evolution took ‘off-the-shelf’ components, like the PSD, and put them together in exciting new ways.

Sponges are the simplest of animals but even they have genetic components of synapsesIn the same way, the PSD of sponges is switched on in a type of cell called the ‘flask cell’. Flask cells are only found in sponge larvae, which, unlike the adults, are free-swimming. These cells could help the larvae to sense their environment, and could well have been a starting point for the evolution of neurons.

Sakarya cautions that there could be another explanation. Sponges could be degenerate relics of a more advanced branch of animals, that stripped away their complexity in favour of life in the (very) slow lane. In this scenario, the flask cells are evolutionary remnants of neurons proper.

Nonetheless, under both scenarios, these findings strongly suggest that the common ancestor of all living animals already has an early working version of the PSD. This practically pre-adapted it for the evolution of nervous systems. With minimal additional evolutionary steps, this early scaffold could have been transformed into the functional synapses that drive our thoughts today. The ancestor was pre-adapted to a future with neurons.

It’s worth noting that this discovery was only made possible because the genome of Amphimedon has been fully sequenced. In an age where genome sequencing could start to be taken for granted, this drives home the importance of sequencing a wide variety of living things that represent crucial junctures in evolution.

Reference: Sakarya, Armstrong, Adamska, Adamski, Wang, Tidor, Degnan, Oakley & Kosik. 2007. A post-synaptic scaffold at the origin of the animal kingdom. PLOS One 6, e506: 1-7.

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Related stories about evolution:
Of flowers and pollinators – a case study in punctuated evolution
Natural selection does a handbrake turn – quick evolution at work
Salamander robot walks, swims and sheds light on evolutionary step from sea to land
Human cone cell lets mice see in new colours
Living optic fibres bypass the retina’s back-to-front structure

Related stories about nervous systems:
Maternal hormone shuts down babies’ brain cells during birth
No new brain cells for you – settling the neurogenesis debate
Bats create spatial memories without making new brain cells

Cultured chimps pass on new traditions between groups

Chimpanzee groups have their own cultural traditions. Now, scientists have shown that chimp groups can transmit new behaviours to each other, by seeding new behaviours into a group and watching them spread.

For humans, our culture is a massive part of our identity, from the way we dress, speak and cook, to the social norms that govern how we interact with our peers. Our culture stems from our ability to pick up new behaviours through imitation, and we are so innately good at this that we often take it for granted.

Chimpanzee groups can learn new traditions from each other.We now know that chimpanzees have a similar ability, and like us, different groups have their own distinct cultures and traditions.

Now, Andrew Whiten from the University of St Andrews has published the first evidence that groups of chimpanzees can pick up new traditions from each other. In an experimental game of Chinese whispers, he seeded new behaviours in one group and saw that they readily spread to others.

Chimp cultures

Many animals have their own cultural traditions. Songbirds, for example, copy their parents’ melodies, and small variations lead to groups with different dialects. But chimpanzees have by far the richest cultures so far observed.

These scope of their culture first came to light in 1999, when Whiten, together with Jane Goodall and others, carefully documented at least 39 cultural behaviours among wild chimpanzees. Many of these were a matter of course in some populations, but completely absent in others.

Some groups use sticks to extract honey, others use them to retrieve marrow from bones, and yet others use them to fish for ants. Some get attention by rapping their knuckles on a branch, while others noisily rip leaves between their teeth. Some groups even have a rain dance.

Whiten has previously published three studies which demonstrated different sides of chimp cultural transmission. The first showed that trained individuals can spread seeded behaviours within a group. The second showed that cultures trickle through the generations as parents teach their children new behaviours. And the third showed that arbitrary conventions such as gestures and displays can spread as easily as skills involving tool use.

Now, together with an international team of researchers from the University of Texas and Yerkes National Primate Research Center, including primate expert Frans de Waal, Whiten has produced the first experimental evidence that cultural transmission can happen between different groups.

Seeding behaviours in groups

Whiten worked with six groups of captive chimps, each consisting of 8-11 individuals. They lived in large but separate enclosures arranged in two rows of three and each group could observe its neighbours, but not interact with them.

Whiten trained one chimp from groups one and four to solve two difficult tasks – the ‘probe task’ and the ‘turn-ip’ task – in order to get some food hidden inside a box. Each chimp was taught to use a different technique.

The probe taskIn the probe task, the chimp could move a lever at the top of the box to open a hatch, and use a stick to impale the food (A). Alternatively, it could use another lever at the side to lift an opening, giving it enough room to manoeuvre a stick inside and push the food out (B).

The turn-ip taskIn the turn-ip task (C), food items were dropped down a pipe, where they were blocked by a disc. The disc had a hole in it, that would allow the food to fall through when it was properly aligned. The chimps could turn the disc either by rotating an exposed edge or using a ratchet. Once the food dropped through, the chimps could get at it by pressing or sliding one of two different handles.

Group transmission

Once the student chimps had mastered their new methods, they were returned to their respective compounds and the whole group was allowed to try its hand at the tasks. Before the training, none of the chimps managed to successfully get at the food. But after just one chimp was taught the technique, most of the others in the group quickly picked it up.

The boxes were then moved to a different position, where chimps from the second pair of groups could watch chimps from the first pair solving the task. After a time, it was moved to another position where the third pair of groups could watch the second one.

Whiten found that the techniques were accurately and quickly transmitted between the different chimpanzee groups. His experiment clearly shows that chimps have an immense capacity for learning new behaviours from their peers. They do this accurately and different groups can acquire and maintain several varied cultural traditions.

Different chimpanzee groups have distinct cultural traditions.In light of this evidence, the regional behaviour patterns seen in chimp groups across Africa are, without a doubt, the result of cultural transmission. In the wild, rival groups are often hostile towards each other and it is unlikely that chimps sit down in jungle conferences to share new ideas. But females do move between groups and Whiten believes that they carry new cultural traditions with them.

How exactly the new behaviours spread is still a matter for debate. Some scientists have suggested that the chimps learn by ‘emulation’, meaning that they focus on the results of actions rather than the actions themselves. But other studies found that chimps don’t respond to ‘ghost’ lessons, where task machinery is operated by remote and not by another chimp.

The most likely explanation is that chimps imitate the actions of other chimps and are very good at learning from each other. In all likelihood, the common ancestor that we share with chimps had the same ability, and also had strong cultural streams running through its populations.

Find out more: If you’re interested in chimp intelligence and evolution, have a look at some of my previous posts on chimp gestures and the evolution of language, the chimp Stone Age and the evolution of tool use, and their use of tools for hunting.

Reference: Whiten, Spiteri, Horner, Bonnie, Lambeth, Schapiro & de Waal. 2007. Transmission of multiple traditions within and between chimpanzee groups. Current Biology 17: 1-6.

Images: Image of experimental apparatus taken from Cell Press.

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