Wednesday, 20 July 2011

Learning about inter-tidal invertebrates

School visit today with the live marine invertebrates I collected yesterday. I would be working with one class year groups year 5 and 6. This visit was part of a larger project that the children were studying called "Oceans Alive" and would provide a local context to the Great Barrier Reef which the children had been learning about.
We started with an introduction to the nature reserve and about how the local coastline was formed.
I also included pictures and information about the beach and tide pools the invertebrates were collected from to set the scene.

Then I worked with each year group separately, observing and discussing the live animals as I demonstrated them one at a time.
I put each invertebrate one at a time underneath the video microscope and the image was projected onto a large screen.
The beadlet anemones are always popular. I put them under while they are closed and then add sea water and they open up. This is how they survive in-between the tides.

We spoke about how they catch their food – which I demonstrated with a piece of food I placed in the tentacles. The anemone reacted immediate firing thousands of stinging cells to paralyze its prey. Without eyes it reacts this way to anything that touches its tentacle, even us but our skin is too thick to harm us.

I demonstrated four crustaceans.
I started with an amphipod and we discussed its body type, where it lives, its senses and what it feds on.

Next the shore crab with its armored shell with jointed limbs like a suit of armour.
The children discussed what they thought the crab might eat and I gave it a small piece of seafood which it held in its pincers and it proceeded to shed into smaller pieces. Shore crabs shed their protective shell when they grow but this also gives them the ability to re-grow a lost limb.
Juvenile shore crabs often have markings that help them to camouflage with their surrounding. This one has white blotches that match the pebbles.
I don’t usually take prawns into schools but as it was a very local school this was not a problem. Being transparent means it is camouflaged where ever it is and you can see some of its internal organs such as the brain.
It picks up bits of food with its delicate pincers and constantly sweeps its surroundings with its long antennae.

A surprise crustacean is the barnacle.
Although it looks like a molluscs, the barnacle spends a moth as a free swimming larvae living in the plankton before it changes shape and sticks itself to a suitable hard surface, a rock a sea defense or even another animal in this case a mussel.

Once secured to the rock it cannot move around. It lives by catching food with its feet (once used for swimming).

I also demonstrated some tiny copepods, no bigger than a large sand grain, these are part of the zoo plankton.

I brought several molluscs, one clam was too big so I kept it in a container.
You can see the siphons used to suck water and food into the shell, the food is filtered out and the water passes over the gills so it feed and respires at the same time.
You can also see the large fleshy foot that is used for burrowing in the sand.

Cockles are small enough to show under the microscope and like the clam they burrow in sand and silt
I also showed a piddock which came from the chalk. The piddock burrows into the chalk by rotating its shell.
Safe inside its burrow the piddock can extend its siphon to feed while still protected by the chalk.

This was a lucky find, a loose piece of chalk and a piddock protruding from the bottom. (When finished I carefully put it back into its burrow.

This mussel has attached itself to the Petri dish by strong threads called byssus which the mussel uses to attach itself to rocks and man-made structures.
On this mussel you can clearly see its foot which is not usually visible.

Edible periwinkle glide along on their foot, this is a gastropod as it only has one shell.
All the above molluscs are bivalves as they have two halves to their shell.

Last of all I showed a small rock pool fish, a blenny.
Like the prawn, I don’t usually take a fish to schools but being very close this was not a problem. This juvenile has extra large pectoral fins making it look like a flying fish.
This small fish can even survive out of the water at low tide as long as it is hidden somewhere cool and damp.

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