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Tuesday, 2 June 2015

Communication


How fish school

During last week’s snorkel around this beautiful little lagoon did you happen to notice all the little fish swimming around near the surface? Ever wondered how they all manage to change direction at the same time? Yes, you can put your towel down and sunbathe now but just take a closer look at this couple of little fellows I’ve just netted. Pretty aren’t they? That dark line going from stem to stern is called the lateral line and it’s packed full of hair cells which can detect minute movements and vibrations in the water. These signals are then sent electronically to the brain giving the fish an extremely accurate picture of its environment even in dark and cloudy waters. They can locate prey, avoid predators and, of course, all turn together in a way that would make any synchronised swimming team give up and take an early shower.

Cardinal Butterfly
This is just one of the methods that animals and plants use to communicate with each other and while we’re sitting here enjoying the sun I thought we’d look at some of the other ways they do it. That stunning Cardinal Butterfly that’s just landed behind us for example. Easily recognisable by the way, from the greenish sheen to its hairs.  Bright coloured butterflies semaphore their colours to each other and even the comparatively plain female Cabbage White gives a brief flash of ultraviolet light on each downstroke of her wings when she’s ready for a mate. So, butterflies too have their flashers, not just the girls after a night out in the bars of Malia.

Blackbird
Birds, as we know, sing beautiful songs, particularly the males when they want to attract a mate but even that is not as simple as it seems. During the reproductive season the blackbird, famous for his ability to improvise and embellish his repertoire, actually sings a simplified, functional version of his song proclaiming ‘here I am’, ‘this is my territory’ ‘ready when you are’. All those twiddly bits and sound incorporations (I knew one once who managed to include a police siren into his song) come later when he has time to relax and experiment.





Now, if you could just move your towel a bit – no, it’s not in my way as such, it’s just that you’ve parked it on an ants’ nest that I wanted to talk about. You didn’t need to move it that far away – or quite so quickly. You’ve disturbed the ants now but still, you’ve created masses of communication in the nest. 

Ants have a sophisticated communications network
Ants are what are known as eusocial insects (which is like social but to a very high degree), living and working almost like a single entity. To get this level of coordination you need a pretty sophisticated communications network and the key to this is pheromones, chemical substances that can be detected by other ants through various sense organs such as their antennae.  Female moths use pheromones as well to attract males over long distances and so do we to a certain extent (ever wondered why you were inexplicably attracted to someone? Pheromones at work). But back to theses ants; as well as chemoreception (the technical term for communicating with pheromones) they are very touchy-feely creatures, passing information by stroking each other with their legs and antennae and they are also surprisingly vocal. We can’t hear them of course but they stridulate like crickets – that is, they rub parts of their bodies together, and produce high pitched chirps. Tree dwelling ants go one better, they also send vibration messages back to the nest by drumming their heads against the wood (the insect world not only has flashers but head bangers as well so when we say that certain disruptive elements in our society are “behaving like animals” maybe we should be more specific and say “behaving like insects.”). So what looks like a mass of confusion down there is a highly complex hub of smells, vibrations and sounds ensuring that every ant knows what it should be doing, and where and when it should be doing it. Amazing little animals, ants. Have you got them all off of your towel yet?

Mallow
But what about plants? The idea of plant communication was ridiculed for years (as in the old song parody: “I talk to the trees, [that’s why they put me away]”) but we are now investigating myriad ways in which plants pass messages to each other. I spotted a little drama unfolding amongst the mallows on our way down here so if you pack up your towel and sun-tan lotion I’ll show you on our way back.



Ant and Aphids ona Mallow leaf
Down here on the leaves we have some newly emerged green aphids and an ant. The aphids want to eat the plant and as they do so they will excrete a sugar rich substance called honeydew. This is what the ant is after. The plant doesn’t want to be eaten so it will mount a chemical defence and produce toxins to deter the aphids. It doesn’t necessarily stop there as we now know that some (maybe all) plants produce pheromones which shout the equivalent of  “APHIDS - INCOMING!” to  their neighbours who can then mount their own defences prior to an attack. The question that arises in my mind is – how does the ant just happen to be there as the aphids emerge? Could be he just stumbled across them but we know that the ants’ main method of communication is based upon pheromone chemoreception so, has the ant picked up the “APHIDS - INCOMING!” transmission? Military intelligence in action as it were. This would be counter productive to the Mallow as the ants will shepherd and protect the aphids from predators such as ladybirds. It’s possible that the plants are aware of the ants’ abilities and send out a scrambled pheromone message that the ants can’t decipher and this one did indeed just get lucky. Or maybe the ant has learnt to decipher the code? As always when we start looking at nature in action there are far more questions than answers.
                                                
Until next week – happy hunting and, as Sherlock Holmes would say: the trick is not just to look but to observe.




As always you can see all the pictures including insets in detail on Flickr
Add your own comments and observations by using the comments button at the foot of the page or find out more about Crete nature by following the links below.

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LINKS:
Naturalists (the facebook page that accompanies this blog)

 










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