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Every day, when the tide retreats, a secret world is exposed. | 0:00:05 | 0:00:09 | |
A magical and intriguing place, | 0:00:09 | 0:00:12 | |
full of remarkable and unusual characters. | 0:00:12 | 0:00:15 | |
SEAGULLS CALL | 0:00:15 | 0:00:17 | |
The rock pool is a cornucopia of life. | 0:00:17 | 0:00:20 | |
It's full of diverse animals. | 0:00:20 | 0:00:23 | |
Some we're familiar with, some we're not. | 0:00:23 | 0:00:25 | |
But this unique environment experiences some of the most | 0:00:25 | 0:00:29 | |
extreme conditions in the natural world. | 0:00:29 | 0:00:32 | |
My name's Professor Richard Fortey. | 0:00:34 | 0:00:36 | |
I just love rootling around in rock pools. | 0:00:36 | 0:00:39 | |
But I'm a palaeontologist, so for me, rock pools are more than | 0:00:39 | 0:00:43 | |
just a collection of wonderful and interesting animals. | 0:00:43 | 0:00:46 | |
They also provide a window into the past. | 0:00:46 | 0:00:49 | |
Part the weeds on any rock pool | 0:00:51 | 0:00:53 | |
and you open the curtains onto a life and death drama | 0:00:53 | 0:00:57 | |
that has been played out for hundreds of millions of years. | 0:00:57 | 0:01:00 | |
Some of the creatures that live here have outlived the dinosaurs, | 0:01:02 | 0:01:05 | |
and have evolved truly extraordinary adaptations to survive. | 0:01:05 | 0:01:09 | |
I want to show you how rock pool creatures have stood | 0:01:12 | 0:01:15 | |
the test of time. | 0:01:15 | 0:01:17 | |
This is the intertidal zone - | 0:01:29 | 0:01:31 | |
the land between the high and low tide marks. | 0:01:31 | 0:01:35 | |
Here, animals have to cope with extreme fluctuations in moisture, | 0:01:35 | 0:01:40 | |
temperature and salinity, as well as predators on land and in sea. | 0:01:40 | 0:01:45 | |
It is a hostile place in which to survive. | 0:01:45 | 0:01:49 | |
As the tide changes, so do conditions on the beach, | 0:01:53 | 0:01:57 | |
and this has a profound effect on all living things, | 0:01:57 | 0:02:01 | |
even the sea weeds. | 0:02:01 | 0:02:03 | |
For more than a billion years, | 0:02:03 | 0:02:05 | |
life on Earth was dominated by very simple single-celled organisms. | 0:02:05 | 0:02:11 | |
Slime, if you like. | 0:02:11 | 0:02:12 | |
This rock's covered in it. | 0:02:12 | 0:02:14 | |
But those organisms included photosynthesising blue-green | 0:02:14 | 0:02:19 | |
bacteria called cyanobacteria that formed living films and breathed | 0:02:19 | 0:02:24 | |
oxygen into the atmosphere, thereby transforming the early Earth. | 0:02:24 | 0:02:30 | |
And about 1.3 billion years ago, they were joined by much larger | 0:02:30 | 0:02:34 | |
multi-celled organisms - algae. | 0:02:34 | 0:02:37 | |
Doing the same job, still photosynthetic, | 0:02:37 | 0:02:40 | |
but these today dominate what we see on the beach and in the rock pools. | 0:02:40 | 0:02:45 | |
Of course, most people know it simply as seaweed. | 0:02:45 | 0:02:48 | |
With more than 9,000 species of seaweed in the UK alone, | 0:02:52 | 0:02:56 | |
the sheer variety and volume of them is staggering. | 0:02:56 | 0:03:01 | |
A quarter of the total global energy captured by photosynthesis is | 0:03:01 | 0:03:06 | |
fixed here in the intertidal zone. | 0:03:06 | 0:03:08 | |
So seaweeds are the basis of a rich and complex food chain. | 0:03:08 | 0:03:14 | |
Constantly changing salinity and exposure can have a dramatic effect | 0:03:16 | 0:03:20 | |
on their survival, and determine where they colonise the beach. | 0:03:20 | 0:03:24 | |
Distinct patterns from upper to lower shore can be seen. | 0:03:26 | 0:03:29 | |
This is known as zonation. | 0:03:29 | 0:03:32 | |
The intertidal zone can be divided into four vertical zones... | 0:03:32 | 0:03:37 | |
Each zone is exposed to moisture, temperature and salinity | 0:03:45 | 0:03:49 | |
in different ways, and this dictates what can survive. | 0:03:49 | 0:03:53 | |
Seaweed produce eggs and sperm. | 0:03:54 | 0:03:57 | |
After 24 hours, the fertilised eggs develop into embryos | 0:03:57 | 0:04:01 | |
which are extremely sensitive to the fluctuating levels of salinity | 0:04:01 | 0:04:06 | |
in each zone. | 0:04:06 | 0:04:08 | |
Exposure to rainwater can have a dramatic effect. | 0:04:10 | 0:04:14 | |
It's dead. | 0:04:17 | 0:04:18 | |
The rainwater penetrates the cells by osmosis, | 0:04:21 | 0:04:24 | |
causing them to swell and burst. | 0:04:24 | 0:04:27 | |
And this is what determines where different species of seaweed | 0:04:30 | 0:04:34 | |
colonise the beach. | 0:04:34 | 0:04:36 | |
The environments in the different intertidal zones play | 0:04:36 | 0:04:39 | |
a vital role in controlling where an organism can survive. | 0:04:39 | 0:04:43 | |
Rock pool animals can go without food for a long time, | 0:04:48 | 0:04:51 | |
they can survive changes in salinity, they're extremely tough. | 0:04:51 | 0:04:56 | |
All this means they've evolved a whole series of adaptations | 0:04:56 | 0:05:00 | |
to cope with life in the in-between zone. | 0:05:00 | 0:05:03 | |
As the tide falls, life becomes very different for the creatures here. | 0:05:05 | 0:05:11 | |
The exposed shore is now subject to unpredictable changes. | 0:05:11 | 0:05:16 | |
Changes that depend on the weather, | 0:05:16 | 0:05:18 | |
the time of year, and the time of day. | 0:05:18 | 0:05:22 | |
Here, temperatures can range from freezing to baking, | 0:05:22 | 0:05:26 | |
oxygen levels fluctuate, | 0:05:26 | 0:05:28 | |
and salinity can increase or decrease, | 0:05:28 | 0:05:31 | |
causing body tissues to dehydrate or swell with water. | 0:05:31 | 0:05:35 | |
But before any of these changes even begin to come into play, | 0:05:35 | 0:05:40 | |
there is a more immediate problem. | 0:05:40 | 0:05:42 | |
There is now less room for everyone to live | 0:05:44 | 0:05:47 | |
and resources are diminished. | 0:05:47 | 0:05:49 | |
Everything is dictated by competition. | 0:05:51 | 0:05:54 | |
Finding a good position becomes a matter of life or death | 0:05:54 | 0:05:58 | |
for all the creatures here. | 0:05:58 | 0:05:59 | |
For anemones, it is important to have a good spot | 0:06:01 | 0:06:04 | |
to catch the most food. | 0:06:04 | 0:06:06 | |
Anemones appear sedentary, but they do move around very slowly. | 0:06:07 | 0:06:11 | |
To find, secure and defend the best spot, they have a secret weapon. | 0:06:14 | 0:06:19 | |
'And to shed some light on their lives, | 0:06:21 | 0:06:23 | |
'Dr Mark Briffa of the University of Plymouth has come into the lab.' | 0:06:23 | 0:06:27 | |
So, Mark, sea anemones are beautiful creatures, | 0:06:28 | 0:06:33 | |
but most people might think that they're pretty inactive, | 0:06:33 | 0:06:36 | |
they just sit there waiting for food to come along. | 0:06:36 | 0:06:39 | |
Yes, they are relatively slow-moving animals, but they are animals | 0:06:39 | 0:06:44 | |
and that means that they have to consume food, | 0:06:44 | 0:06:46 | |
and one of the things that sea anemones have to do | 0:06:46 | 0:06:49 | |
before they can consume it is to capture their food. | 0:06:49 | 0:06:52 | |
Can you see the feeding tentacles? | 0:06:52 | 0:06:55 | |
There are six rows of tentacles on the top of the animal, 192 in total, | 0:06:55 | 0:06:59 | |
and just by looking at them for a small amount of time, | 0:06:59 | 0:07:02 | |
you can see that the tentacles are moving about, | 0:07:02 | 0:07:05 | |
and these tentacles are there to trap food and bring it in | 0:07:05 | 0:07:09 | |
towards this structure in the middle of the animal. | 0:07:09 | 0:07:12 | |
This is the oral disc. | 0:07:12 | 0:07:13 | |
-Otherwise known as a mouth. -A mouth, yeah. | 0:07:13 | 0:07:15 | |
'Nematocysts are stinging cells | 0:07:16 | 0:07:18 | |
'common to all anemones and jellyfish.' | 0:07:18 | 0:07:20 | |
'When stimulated, they fire a venomous dart | 0:07:22 | 0:07:25 | |
'attached to a thread into their prey.' | 0:07:25 | 0:07:27 | |
We can look at the use of the tentacles to trap food | 0:07:29 | 0:07:32 | |
by taking a small piece of food - this is a little piece of limpet - | 0:07:32 | 0:07:37 | |
and dropping it over the ring of tentacles. | 0:07:37 | 0:07:41 | |
They kind of close in on it and pull it down. | 0:07:41 | 0:07:44 | |
Oh, it likes that. It likes that a lot. | 0:07:44 | 0:07:46 | |
It's closing all six rings, | 0:07:46 | 0:07:48 | |
it's pushed the food back down towards its mouth. | 0:07:48 | 0:07:52 | |
And they're not just for trapping prey, either. | 0:07:52 | 0:07:54 | |
In this species of sea anemone, | 0:07:54 | 0:07:56 | |
there are specialised tentacles simply for fighting... | 0:07:56 | 0:08:00 | |
..and these specialised tentacles appear as little blue beadlets | 0:08:01 | 0:08:06 | |
in a ring around the outside of the six rings of the feeding tentacles, | 0:08:06 | 0:08:11 | |
and they will use them in combat with rival anemones | 0:08:11 | 0:08:14 | |
of the same species, and therefore require exactly the same resources | 0:08:14 | 0:08:20 | |
in terms of a good place in the rock pool. | 0:08:20 | 0:08:22 | |
'Using a specialist time-lapse camera, | 0:08:25 | 0:08:28 | |
'we can speed these battles up to see what's really happening.' | 0:08:28 | 0:08:31 | |
'Twisting their flexible bodies, anemones take aggressive swipes | 0:08:33 | 0:08:37 | |
'at each other, tearing off ribbons of skin.' | 0:08:37 | 0:08:40 | |
'Losers have no choice but to find another place to settle.' | 0:08:44 | 0:08:48 | |
'We may barely give anemones a second glance, | 0:08:58 | 0:09:02 | |
'but their remarkable fighting behaviour has allowed them | 0:09:02 | 0:09:05 | |
'to colonise the most sought-after locations in the rock pool, | 0:09:05 | 0:09:08 | |
'and has helped them thrive on our beaches | 0:09:08 | 0:09:11 | |
'for around 540 million years.' | 0:09:11 | 0:09:14 | |
'Other creatures have dealt with the lack of space very differently.' | 0:09:16 | 0:09:20 | |
'They have left the pools altogether, taking up residence | 0:09:20 | 0:09:24 | |
'on the rocks where they are exposed at low tide.' | 0:09:24 | 0:09:27 | |
'Around 530 million years ago, molluscs developed hard shells | 0:09:29 | 0:09:34 | |
'to house their soft body parts, | 0:09:34 | 0:09:37 | |
'creating a microclimate into which they could retreat.' | 0:09:37 | 0:09:41 | |
And one of the first animals to do this is still with us. | 0:09:41 | 0:09:44 | |
It's a living fossil. The chiton. | 0:09:44 | 0:09:47 | |
The chiton has a number of plates which allow it to shuffle around | 0:09:48 | 0:09:52 | |
and grip tightly to the surface of the rock. | 0:09:52 | 0:09:55 | |
But an even more effective way of doing this is under a single shell, | 0:09:55 | 0:09:59 | |
and the mollusc that has done this most successfully | 0:09:59 | 0:10:02 | |
is still with us in every rock pool and on every rocky shore. | 0:10:02 | 0:10:05 | |
It's the limpet. | 0:10:05 | 0:10:06 | |
'Professor Stephen Hawkins of the University of Southampton | 0:10:09 | 0:10:13 | |
'is a limpet expert.' | 0:10:13 | 0:10:14 | |
I'm told that they vary in conicality | 0:10:16 | 0:10:18 | |
according to where they are on the shore. | 0:10:18 | 0:10:20 | |
Yes, and also with age. | 0:10:20 | 0:10:23 | |
I think as they get bigger and older, they tend to get more conical, | 0:10:23 | 0:10:27 | |
and it makes quite a lot of sense to be conical like this, | 0:10:27 | 0:10:29 | |
because the circumference is where water gets lost when the tide's out. | 0:10:29 | 0:10:34 | |
'Retaining moisture is vital if the limpet is to survive | 0:10:37 | 0:10:40 | |
'the drying effects of the sun.' | 0:10:40 | 0:10:42 | |
They've got a big extensive foot, you can see on this animal here, | 0:10:46 | 0:10:51 | |
and essentially, it's a very complicated | 0:10:51 | 0:10:53 | |
biological suction device. That's how it works. | 0:10:53 | 0:10:56 | |
'This adaptation allows them to hold on to the rock | 0:10:57 | 0:11:00 | |
'and resist the force of the waves.' | 0:11:00 | 0:11:02 | |
'Surprisingly, limpets are territorial. | 0:11:04 | 0:11:07 | |
'They create a depression in the rock known as a home scar.' | 0:11:07 | 0:11:10 | |
'As the tide starts to go down | 0:11:11 | 0:11:13 | |
'they return to this place and hunker securely down.' | 0:11:13 | 0:11:16 | |
'Territorial fights are common, and losers are prised off the rock.' | 0:11:21 | 0:11:25 | |
'As the tide covers them, | 0:11:28 | 0:11:29 | |
'limpets leave their home scars and begin to feed.' | 0:11:29 | 0:11:32 | |
'Limpets are very important grazers on the seashore. | 0:11:34 | 0:11:37 | |
'However, there is intense competition.' | 0:11:37 | 0:11:40 | |
'To see exactly what impact this has, | 0:11:41 | 0:11:43 | |
'we have to go to the laboratory.' | 0:11:43 | 0:11:46 | |
I collected these this morning at low tide | 0:11:46 | 0:11:48 | |
just as the tide was about to come over them, | 0:11:48 | 0:11:50 | |
so we should be able to stimulate them to set off on | 0:11:50 | 0:11:54 | |
their foraging excursions to go off feeding, if we put them in the tank. | 0:11:54 | 0:11:57 | |
It doesn't take long before they sense they're surrounded with water. | 0:12:05 | 0:12:09 | |
Little tentacles coming out? | 0:12:09 | 0:12:12 | |
Yes, they have these fantastic sensory tentacles | 0:12:12 | 0:12:14 | |
all the way round the edge of the shell. | 0:12:14 | 0:12:16 | |
The big ones, the primary tentacles, actually match with those rays | 0:12:16 | 0:12:20 | |
you can see on the shell, and there's smaller tentacles | 0:12:20 | 0:12:23 | |
in between, and that gives lots of information about the physical | 0:12:23 | 0:12:27 | |
and biological environment when they're out foraging. | 0:12:27 | 0:12:30 | |
And foraging means scraping algae and other things | 0:12:30 | 0:12:34 | |
off the surface of the rock. | 0:12:34 | 0:12:35 | |
That's right. They feed by scraping the rock surface | 0:12:35 | 0:12:38 | |
using their radula, yes. | 0:12:38 | 0:12:39 | |
'The radula of the limpet is a ribbon-like tongue | 0:12:41 | 0:12:44 | |
'covered in teeth. | 0:12:44 | 0:12:45 | |
'It moves back and forth, scraping algal slime from the rocks.' | 0:12:46 | 0:12:49 | |
'The limpet's radula is tipped with haematite, | 0:12:51 | 0:12:53 | |
'an extremely hard material that allows the limpets | 0:12:53 | 0:12:56 | |
'to graze on hard surfaces.' | 0:12:56 | 0:12:58 | |
Stephen's research has shown that limpets have a profound effect | 0:13:00 | 0:13:03 | |
on the ecology of the seashore. | 0:13:03 | 0:13:05 | |
When they're off foraging, and this is where I fenced the rock | 0:13:05 | 0:13:09 | |
to keep limpets out, | 0:13:09 | 0:13:10 | |
and all the rest of the area here is where limpets were able | 0:13:10 | 0:13:13 | |
to forage freely, and just six months later... | 0:13:13 | 0:13:15 | |
Wow. | 0:13:15 | 0:13:16 | |
Yes, it's amazing, isn't it? | 0:13:16 | 0:13:17 | |
Six months later there's a really dense growth of seaweeds, | 0:13:17 | 0:13:21 | |
bladder wrack, fucoids, covering the rock in the absence | 0:13:21 | 0:13:25 | |
of the limpet grazing, so basically, | 0:13:25 | 0:13:27 | |
the limpets, through their radulae, really control the algae. | 0:13:27 | 0:13:30 | |
'So although limpets appear to be immobile and stuck to the rocks, | 0:13:32 | 0:13:36 | |
'in fact, they have a much more complicated life cycle | 0:13:36 | 0:13:40 | |
'that plays an important part in the ecology of the intertidal zone.' | 0:13:40 | 0:13:44 | |
'The rising tide gives animals an opportunity to hunt for food, | 0:13:49 | 0:13:54 | |
'but this also means they can become the hunted.' | 0:13:54 | 0:13:56 | |
'Starfish belong to a phylum of animals called the echinoderms, | 0:14:00 | 0:14:04 | |
'which first appeared in the fossil record | 0:14:04 | 0:14:05 | |
'more than 500 million years ago.' | 0:14:05 | 0:14:07 | |
'Starfish have macabre eating habits. | 0:14:08 | 0:14:11 | |
'Using their strong sticky tube feet, | 0:14:13 | 0:14:15 | |
'they force open the shells of molluscs and then, | 0:14:15 | 0:14:19 | |
'pushing their stomach out through their mouth, | 0:14:19 | 0:14:21 | |
'they digest the animal inside.' | 0:14:21 | 0:14:23 | |
'Limpets have been locked in an arms race with starfish for millions | 0:14:31 | 0:14:35 | |
'of years, and have evolved their own way of dealing with them.' | 0:14:35 | 0:14:39 | |
So what are we looking for here? | 0:14:41 | 0:14:44 | |
What happens, usually, is that the limpets get agitated | 0:14:44 | 0:14:48 | |
when they sense a predator in the area and then, | 0:14:48 | 0:14:50 | |
when the starfish is in contact with the limpet, | 0:14:50 | 0:14:53 | |
the limpet tends to raise up | 0:14:53 | 0:14:54 | |
and then it will often stamp down on the starfish and maybe drive it off. | 0:14:54 | 0:14:59 | |
'In a rock pool, | 0:15:05 | 0:15:06 | |
'there is nothing quite as sinister as a marauding starfish.' | 0:15:06 | 0:15:10 | |
'Small limpets have no choice but to flee.' | 0:15:22 | 0:15:25 | |
'A lucky escape.' | 0:15:28 | 0:15:30 | |
'Large limpets, however, stand their ground.' | 0:15:34 | 0:15:37 | |
'Using the edge of the shell, a limpet can push the starfish away | 0:15:43 | 0:15:47 | |
'to prevent it climbing on top.' | 0:15:47 | 0:15:49 | |
Look at that! | 0:15:49 | 0:15:51 | |
'Continually scraping at the arm can damage the tube feet, | 0:15:51 | 0:15:54 | |
'deterring an attack.' | 0:15:54 | 0:15:56 | |
I don't think I'd like to be approached by a great battery | 0:15:58 | 0:16:01 | |
of wiggly tube feet, if I was a limpet. | 0:16:01 | 0:16:03 | |
There he goes. Look at that. | 0:16:03 | 0:16:05 | |
It's really very agitated. | 0:16:06 | 0:16:08 | |
Well, we can't say that rock pools lack drama. | 0:16:08 | 0:16:11 | |
'Unseen by us, | 0:16:17 | 0:16:18 | |
'there are many battles being fought beneath the waves.' | 0:16:18 | 0:16:21 | |
'Over time, predators and prey have developed a range of adaptations | 0:16:22 | 0:16:27 | |
'to attack and defend.' | 0:16:27 | 0:16:28 | |
This is a dog whelk. | 0:16:29 | 0:16:32 | |
A fearsome predator in the rock pools. | 0:16:32 | 0:16:34 | |
'This carnivore has devised an ingenious way | 0:16:36 | 0:16:39 | |
'of hunting other molluscs... | 0:16:39 | 0:16:41 | |
'..and one of its favourite prey are mussels.' | 0:16:43 | 0:16:46 | |
'Mussels are filter feeders sieving off the abundant food | 0:16:50 | 0:16:53 | |
'that drifts in the upper ocean.' | 0:16:53 | 0:16:54 | |
'They attach themselves to the rock surface by strong threads | 0:16:57 | 0:17:00 | |
'which they secrete through their muscular foot.' | 0:17:00 | 0:17:03 | |
'These threads enable them to cling to the rocks, | 0:17:05 | 0:17:08 | |
'despite the relentless pounding of the ocean waves.' | 0:17:08 | 0:17:11 | |
However, the stationary mussel | 0:17:13 | 0:17:16 | |
is an easy target for prowling dog whelks. | 0:17:16 | 0:17:19 | |
Their lethal weapon is a radula. | 0:17:21 | 0:17:24 | |
A short, horny ribbon containing many rows of teeth, | 0:17:25 | 0:17:28 | |
which are used like a file in combination with an acid secretion, | 0:17:28 | 0:17:32 | |
to drill through the shells and tear the flesh of the mussel. | 0:17:32 | 0:17:36 | |
It's a gruesome attack. | 0:17:38 | 0:17:39 | |
Mussels, however, can turn the tables on a dog whelk. | 0:17:42 | 0:17:45 | |
Sensing a nearby attack, others in the colony | 0:17:46 | 0:17:49 | |
start to produce more and more sticky threads. | 0:17:49 | 0:17:51 | |
If they make contact, it can spell doom for the dog whelk, | 0:17:53 | 0:17:56 | |
which will starve to death. | 0:17:56 | 0:17:58 | |
The hard shell of molluscs like the dog whelk | 0:18:03 | 0:18:07 | |
persist long after the soft parts of the animal itself have decayed away, | 0:18:07 | 0:18:12 | |
but these empty shells don't go to waste. | 0:18:13 | 0:18:15 | |
In the rock pool, when one species dies or moves on, | 0:18:19 | 0:18:23 | |
another takes over. | 0:18:23 | 0:18:24 | |
Empty shells are put to good use | 0:18:27 | 0:18:28 | |
by one of my favourite rock pool creatures - hermit crabs. | 0:18:28 | 0:18:33 | |
Hermit crabs use shells as a very effective defence against predators, | 0:18:34 | 0:18:38 | |
and their bodies have evolved to fit them perfectly. | 0:18:38 | 0:18:42 | |
Unlike other crabs, their abdomen has become soft | 0:18:43 | 0:18:46 | |
and asymmetrical, and their back legs are very reduced, | 0:18:46 | 0:18:49 | |
allowing them to fit inside shells. | 0:18:49 | 0:18:52 | |
The asymmetry of their claws also allows them to close up | 0:18:53 | 0:18:57 | |
the entrance to the shell as a defence against predators. | 0:18:57 | 0:19:00 | |
The crab's shell must not only be tough enough to withstand an attack, | 0:19:03 | 0:19:07 | |
it must also afford it some camouflage. | 0:19:07 | 0:19:09 | |
So these shells are obviously a protection. | 0:19:11 | 0:19:14 | |
That's right. | 0:19:14 | 0:19:15 | |
But are the crabs even choosier | 0:19:15 | 0:19:17 | |
about which types of shells they pick up? | 0:19:17 | 0:19:20 | |
The crabs are incredibly choosy about what they want. | 0:19:20 | 0:19:24 | |
They'll spend a lot of time and effort deciding | 0:19:24 | 0:19:27 | |
whether to change shells, whether a potential new shell is a good one. | 0:19:27 | 0:19:31 | |
I mean, they're also known to be particular about the colour of the | 0:19:31 | 0:19:36 | |
shell, at least in terms of if it's contrast against the background. | 0:19:36 | 0:19:42 | |
We can run a little experiment here, so what I have are two containers | 0:19:42 | 0:19:45 | |
with a dark coloured substrate, | 0:19:45 | 0:19:47 | |
and I have some littorina obtusata shells. | 0:19:47 | 0:19:52 | |
These are called citrina and dark reticulata. | 0:19:52 | 0:19:55 | |
The only thing that's really different about them is the colour. | 0:19:55 | 0:19:59 | |
What I'm going to do is place these shells, so you can see straight away | 0:19:59 | 0:20:03 | |
that, to our eyes at least, the citrina shells really stand out, | 0:20:03 | 0:20:08 | |
and the dark reticulata shells don't stand out so much. | 0:20:08 | 0:20:11 | |
So I'm going to take four crabs in the citrina shells... | 0:20:11 | 0:20:14 | |
..and give them the option to move into the empty black shells. | 0:20:17 | 0:20:23 | |
Now, the other half of the experiment | 0:20:23 | 0:20:25 | |
is to take four crabs in dark reticulata shells. | 0:20:25 | 0:20:28 | |
So I'll find those. | 0:20:28 | 0:20:29 | |
If you fish out four crabs in dark reticulata shells. | 0:20:29 | 0:20:32 | |
One, two, three, four. There we go. | 0:20:32 | 0:20:36 | |
We'll put them into here, | 0:20:36 | 0:20:37 | |
and these guys have the option of moving into citrina shells. | 0:20:37 | 0:20:40 | |
So these crabs can move into shells that blend in, | 0:20:40 | 0:20:43 | |
and these crabs can move into shells that stand out. | 0:20:43 | 0:20:46 | |
Very particular about moving into new shells. | 0:20:46 | 0:20:48 | |
They want to make sure that a new shell is absolutely better | 0:20:48 | 0:20:51 | |
than the shell they're coming out of. | 0:20:51 | 0:20:53 | |
I think he's going to come out. There he goes. | 0:20:53 | 0:20:55 | |
Swapped shells, there we go. Gone from yellow into dark, | 0:20:55 | 0:21:00 | |
and I can count here that three of the crabs are in dark shells. | 0:21:00 | 0:21:04 | |
And blending in well with the background. | 0:21:04 | 0:21:09 | |
'Whereas the ones in the dark shells stay where they are.' | 0:21:09 | 0:21:12 | |
What it shows overall if we'd run this experiment lots and lots | 0:21:13 | 0:21:16 | |
of times, the overall trend would be that significantly more crabs | 0:21:16 | 0:21:21 | |
would be in the darker coloured shells, and that just goes to show | 0:21:21 | 0:21:24 | |
how important blending into the background is for these animals. | 0:21:24 | 0:21:27 | |
'Choosing their shells carefully is a matter of survival | 0:21:29 | 0:21:32 | |
'for the hermit crab, | 0:21:32 | 0:21:34 | |
'as this affords it the camouflage and protection it needs | 0:21:34 | 0:21:37 | |
'to hide from roaming predators.' | 0:21:37 | 0:21:39 | |
'Anticipating tidal change | 0:21:45 | 0:21:47 | |
'is a problem all rock pool creatures face.' | 0:21:47 | 0:21:50 | |
'Dr David Wilcockson of the University of Aberystwyth | 0:21:52 | 0:21:55 | |
'is going to show me how animals are adapted to cope with this.' | 0:21:55 | 0:21:58 | |
So the tide is out, | 0:21:59 | 0:22:01 | |
and the question is how do the organisms on the beach | 0:22:01 | 0:22:05 | |
know when it is coming in? | 0:22:05 | 0:22:06 | |
That's actually a very good question, | 0:22:07 | 0:22:09 | |
because all organisms, including ourselves, | 0:22:09 | 0:22:12 | |
have biological clocks which enable us to anticipate changes | 0:22:12 | 0:22:16 | |
in our environment such as night and day, | 0:22:16 | 0:22:19 | |
and in this case, the incoming and outgoing of the tides, | 0:22:19 | 0:22:21 | |
and this organism we have buzzing around in these tanks | 0:22:21 | 0:22:25 | |
is the marine equivalent of the woodlouse. | 0:22:25 | 0:22:28 | |
It's an animal called Eurydice pulchra, | 0:22:30 | 0:22:33 | |
and Eurydice has a very good 12.4 hour, or tidal clock, | 0:22:33 | 0:22:38 | |
whereas ours is run on a 24-hour basis. | 0:22:38 | 0:22:41 | |
And they come out of the sand and swim when the tide is in, | 0:22:41 | 0:22:45 | |
and feed and breed, and then what they'll do | 0:22:45 | 0:22:47 | |
before the tide goes out is actually bury back into the sand | 0:22:47 | 0:22:51 | |
so they maintain their preferred position on the shore. | 0:22:51 | 0:22:54 | |
'Maintaining the best position on the shore | 0:22:55 | 0:22:57 | |
'is essential for survival.' | 0:22:57 | 0:22:59 | |
'To best illustrate tidal rhythms, | 0:23:00 | 0:23:02 | |
'David has devised a unique experiment.' | 0:23:02 | 0:23:05 | |
So what we have here, Richard, is activity monitors, | 0:23:05 | 0:23:09 | |
and in each tube is a little bit of sand and some seawater, | 0:23:09 | 0:23:13 | |
and there is an individual Eurydice in each of these tubes | 0:23:13 | 0:23:16 | |
and they are all inactive at the moment, | 0:23:16 | 0:23:18 | |
because currently they are expecting it to be low water. | 0:23:18 | 0:23:21 | |
When they expect high water, they will start to swim, | 0:23:23 | 0:23:26 | |
and across each tube is a little infrared beam, | 0:23:26 | 0:23:29 | |
and when they swim through that beam, the beam is broken | 0:23:29 | 0:23:33 | |
and the beam break is recorded on the computer. | 0:23:33 | 0:23:37 | |
I see. | 0:23:37 | 0:23:38 | |
We can actually turn those recordings into plots, | 0:23:38 | 0:23:40 | |
so we can visualise the activity, | 0:23:40 | 0:23:42 | |
and this is a plot from one individual Eurydice, | 0:23:42 | 0:23:47 | |
and you can see these black bars here | 0:23:47 | 0:23:49 | |
represent beam breaks or activity periods, | 0:23:49 | 0:23:52 | |
and these bouts of activity are occurring every 12.4 hours. | 0:23:52 | 0:23:55 | |
On the nail. | 0:23:55 | 0:23:57 | |
A very precise 12.4 hour rhythm, | 0:23:57 | 0:23:59 | |
so we can actually show they have a tidal rhythm, | 0:23:59 | 0:24:01 | |
and the important thing is that this rhythm will continue | 0:24:01 | 0:24:04 | |
in the absence of any tides. | 0:24:04 | 0:24:06 | |
'The tide outside has now risen, and there is a definite change | 0:24:15 | 0:24:19 | |
'in activity of our subjects.' | 0:24:19 | 0:24:20 | |
Well, there's an amazing sight. | 0:24:22 | 0:24:23 | |
It's been a few hours since we looked at them last, | 0:24:23 | 0:24:26 | |
and we can see now that they think it is high tide, | 0:24:26 | 0:24:28 | |
or they're expecting it to be high tide, | 0:24:28 | 0:24:30 | |
and they're zooming up and down, crossing the infrared beam. | 0:24:30 | 0:24:34 | |
I can see the numbers going up. | 0:24:34 | 0:24:35 | |
That's right, and those beam breaks are being recorded | 0:24:35 | 0:24:38 | |
on the monitor here. | 0:24:38 | 0:24:40 | |
So, in nature, this is when they'd be feeding and on the hunt. | 0:24:40 | 0:24:43 | |
That's right, yeah. | 0:24:43 | 0:24:44 | |
But obviously this internal clock needs some controls on it. | 0:24:44 | 0:24:49 | |
I mean, are there things in the natural environment | 0:24:49 | 0:24:52 | |
that help set those controls? | 0:24:52 | 0:24:53 | |
There are. What happens is that each individual animal, | 0:24:53 | 0:24:57 | |
its clock will be slightly different to the next one. | 0:24:57 | 0:25:01 | |
-Their clocks drift out of phase... -Right. | 0:25:01 | 0:25:04 | |
..with the natural cycle, if we remove it | 0:25:04 | 0:25:06 | |
from its natural environment. | 0:25:06 | 0:25:08 | |
So the incoming and outgoing tide | 0:25:08 | 0:25:10 | |
actually re-synchronises their clock. | 0:25:10 | 0:25:13 | |
Life in rock pools is more complicated than we thought. | 0:25:13 | 0:25:16 | |
I think it's far more complicated than we thought, yes. | 0:25:16 | 0:25:19 | |
Creatures of the rock pool provide one of the most sensitive | 0:25:26 | 0:25:29 | |
barometers to monitor the way our natural environment is changing. | 0:25:29 | 0:25:34 | |
'Like all intertidal animals, barnacles have to deal with | 0:25:36 | 0:25:40 | |
'fluctuating conditions on both a daily and seasonal basis.' | 0:25:40 | 0:25:43 | |
'However, recent research suggests that barnacles and other creatures | 0:25:46 | 0:25:50 | |
'have to cope with changes over a much bigger timescale. | 0:25:50 | 0:25:54 | |
'Changes that we may be responsible for.' | 0:25:54 | 0:25:57 | |
'Nova Mieskowska of the Marine Biological Association | 0:25:59 | 0:26:03 | |
'has been analysing long-term data on barnacles here in Devon.' | 0:26:03 | 0:26:08 | |
We've found over the many decades that we've been studying barnacles | 0:26:09 | 0:26:13 | |
all around the UK, but especially down in the southwest here, | 0:26:13 | 0:26:17 | |
that the warm water barnacles, which you can see around here | 0:26:17 | 0:26:20 | |
with the slightly more greenish tinges, they're kite-shaped. | 0:26:20 | 0:26:24 | |
These warm water barnacles have become a lot more abundant, | 0:26:24 | 0:26:27 | |
especially over the last 20, 25 years since climate change | 0:26:27 | 0:26:30 | |
really started to take hold. | 0:26:30 | 0:26:33 | |
Their northern limits are in Scotland | 0:26:33 | 0:26:34 | |
for the warm water barnacles, | 0:26:34 | 0:26:36 | |
and they go all the way down south, | 0:26:36 | 0:26:38 | |
past the Mediterranean and slightly into north Africa | 0:26:38 | 0:26:41 | |
whereas the cold water barnacles, | 0:26:41 | 0:26:43 | |
these are the ones that are slightly whiter. | 0:26:43 | 0:26:46 | |
Here's one. You can see. This is Semibalanus Balanoides here. | 0:26:46 | 0:26:49 | |
Oh, I can see now, yes. You have to get your eye in, don't you? | 0:26:49 | 0:26:52 | |
Their northern limits go way up into the Arctic Circle, | 0:26:52 | 0:26:56 | |
but their southern limits have been cut back and back further north. | 0:26:56 | 0:26:59 | |
They used to be in northern Spain around the Bay of Biscay, | 0:26:59 | 0:27:02 | |
where there has been a big trimming northwards | 0:27:02 | 0:27:04 | |
because it's just plainly too warm for them to live there any more. | 0:27:04 | 0:27:08 | |
And we're even seeing the effects here in the southwest. | 0:27:08 | 0:27:11 | |
We've seen a massive decline | 0:27:11 | 0:27:12 | |
in the survival of these cold water barnacles. | 0:27:12 | 0:27:16 | |
And have we got their natural predators | 0:27:16 | 0:27:17 | |
dotted around on the surface? | 0:27:17 | 0:27:19 | |
Yes. You can see that we've got some marauding dog whelks, | 0:27:19 | 0:27:23 | |
and these dog whelks do preferentially | 0:27:23 | 0:27:25 | |
eat the cold water barnacles Semibalanus Balanoides, | 0:27:25 | 0:27:28 | |
so it will be very interesting to see whether, | 0:27:28 | 0:27:30 | |
when we lose these for good in the southwest, | 0:27:30 | 0:27:33 | |
whether the dog whelks will actually be able to change | 0:27:33 | 0:27:35 | |
and then feed entirely on the warm water barnacle or not. | 0:27:35 | 0:27:39 | |
Well, I guess the story of evolution is often change or die. | 0:27:39 | 0:27:42 | |
Yes. | 0:27:42 | 0:27:43 | |
It is alarming to think that we might be responsible | 0:27:46 | 0:27:48 | |
for affecting the survival of the creatures we know and love so well. | 0:27:48 | 0:27:53 | |
However, because they have adapted to one of the toughest places | 0:27:56 | 0:27:59 | |
on Earth, rock pool animals have outlived many other species | 0:27:59 | 0:28:04 | |
they shared the seas with. | 0:28:04 | 0:28:06 | |
'As a palaeontologist, I marvel to think that their ancestors | 0:28:06 | 0:28:10 | |
'lived alongside fossil species I have studied, | 0:28:10 | 0:28:13 | |
'but whose lives I can only really imagine.' | 0:28:13 | 0:28:15 | |
'And rock pool animals may well outlive us. | 0:28:17 | 0:28:21 | |
'For if anything has got what it takes to endure, it is them, | 0:28:21 | 0:28:25 | |
'for they are masters of an ever-changing environment.' | 0:28:25 | 0:28:28 | |
Subtitles by Red Bee Media Ltd | 0:28:52 | 0:28:55 |