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To Ponder: Meant to be Naturalists

20150909_142132-1“It would be well if all we persons in authority, parents and all who act for parents, could make up our minds that there is no sort of knowledge to be got in these early years so valuable to children as that which they get for themselves of the world they live in.  Let them once get touch with Nature, and a habit is formed which will be a source of delight through life.  We are all meant to be naturalists, each in his degree, and it is inexcusable to live in a world so full of the marvels of plant and animal life and to care for none of these things.”  — Charlotte Mason (I.61)

Out & About: Water Striders

water striderWhat an adventure we had today!  We started out in a sunny field full of wildflowers and grasshoppers and ended up soaked to the skin but oh-so-joyful!  Our Nature Study class met beside a meandering stream at a friend’s farm to learn about an amazing aquatic insect:  The Water Strider.

OBJECT LESSON:

Also known as “Jesus Bugs,” water striders  literally walk on water!  They use something called the “surface tension” of the water to their advantage.  Water molecules are attracted to each other and like to stay together, especially on the surface where there is only air above.  Since there are no water molecules above the surface for them to hold onto, the molecules at the surface cling extra tightly to the molecules beside them and under them — so tight, in fact, that a “skin” seems to form on the surface.  Water striders walk on this thin membrane.  Here’s a cool slow-motion video of them in action:  https://www.youtube.com/watch?v=RphuMEUY3Og

But water striders have another secret for walking on water — their legs!  The legs have tiny hairs that repel water and trap air.  By repelling water, the tiny insects stand on the water’s surface and the trapped air allows them to float and move easily — almost as if they were skating!

And finally, water striders are very, very lightweight.  So much so that they are able to float.  Lily pads and twigs float because the water is pushing up on them, but a rock dropped into the water sinks rapidly because it’s so heavy for its size that it overcomes the “push” of the water.

Using a large bowl filled with water, I asked the class to predict from their size, weight and shape whether these items would sink or float:  Paper clip, straight pin, bottle cap, coin, cotton ball, rubber band.  Only the bottle cap and cotton ball floated (and the cotton ball sank when it finally became saturated).

Using the surface of the water like a trampoline, water striders can jump into the air to avoid predators or catch prey!  Jumping requires a large amount of force on the starting surface.  Easy enough on terra firma, right?  But jumping on water is much more difficult because too much force will break the surface tension.  Recently mechanical engineers from Seoul National University have developed a robotic insect that can jump on water, too.  Researchers say this technology could someday be used in surveillance missions.  Watch! https://www.youtube.com/watch?v=Z83l347rh6E

Water striders can live for many months, and adults can overwinter by crawling inside a plant stem when it gets too cold.

FIELD WORK:

Like all insects, water striders have six legs, and each set has a different use.  I asked the students to observe water striders in the stream and try to determine to what use the insects puts each set of legs.  (They use their front legs to catch and hold prey, their middle legs to row, and their hind legs to steer.)

If there is time, observe what water striders eat and how they eat it.  (Water striders are carnivorous and use their piercing mouth parts to inject a chemical that liquifies the prey’s internal structure so they may then suck them dry.  They will eat whatever falls into the water (other insects, worms, honeybees) and use their front legs to find food by sensing ripples made by struggling prey, then grab and hold it while they drink its life juices.  Here’s a not-gross video of water striders catching and enjoying a meal:  https://www.youtube.com/watch?v=SVoG0Uy_uQ8

Try to determine what preys on water striders.  (fish, frogs, salamanders)

WRAP-UP:

A violent thunderstorm with dangerous lightning caused our class to be cut short, but some of the students recorded their observations at home.

DSC00995DSC00921

 

 

 

 

 

 

 

 

A few of us were able to wait out the storm and take a walk into the woods along the creek bank.  In addition to a perfectly-preserved, bleached-out cricket exoskeleton, a mystery nut (which turned out to be an immature beechnut)  and some nearly translucent, gelatinous, very slimy fungus (maybe snow fungus?), we found  the most amazing deep aquamarine bracket fungus growing on a fallen log.  What a treasure!  It looked just like this (only much more of it):

Bright blue bracket fungus.

To Ponder: Believe in Miracles?

WE LIVE ON A BLUE PLANET

THAT CIRLES AROUND A BALL OF FIRE

NEXT TO A MOON THAT MOVES THE SEA,

…AND YOU DON’T BELIEVE IN MIRACLES?

— Anonymous

 

Out & About: Freshwater Mussels

mussel1What has a mouth but does not eat, always murmurs but never talks, has a bed but does not sleep, always runs and never walks?  A river, of course!

Today our Nature Study class went snorkeling in the Clinch River near Natural Tunnel State Park in Duffield, Virginia, to get up-close-and-personal with freshwater mussels.  Rare and endangered species abound in the Appalachian and Smoky Mountains, and the Clinch River alone sustains 48 imperiled and vulnerable animal species — including 29 varieties of rare freshwater mussels.  Because of this concentration of rare animals, the Clinch River has been identified as the number one hotspot in the US for imperiled aquatic species.

The Clinch is home to 45 species of freshwater mussels.  Appalachian mussels have terrific names like PURPLE WARTYBACK, SHINY PIGTOE, MONKEYFACE, and PEARLYMUSSEL.  Although they all look pretty much alike to the untrained eye, their astonishing diversity is one of the Clinch’s main claims to fame.  For a bit of perspective, you’d have to explore every stream in Europe and temperate Asia to find as many species!

OBJECT LESSON:

Mussels live in a variety of aquatic habitats, but all require areas where the running water has a high oxygen content and supplies a rich food source of organic particles.  The constant flow of water also removes waste materials that would be toxic to the mussels, so they are important indicators of water quality.  The best substrate (stream bed) for freshwater mussels is a combination of silt, sand, gravel or cobble with little sedimentation.

Adult mussels are sedentary, moving no more than a few feet along the bottoms of the rivers during their entire lifetime, and spending their time flushing water through their bodies and extracting microscopic organisms to eat.  The young, however, experience a more adventurous beginning.  Each species of mussel has a different species of host fish which it uses as its “nursery.”  Female mussels trick fish into coming close by showing off fleshy appendages that act as bait.  When a fish swoops close to eat the “bait” the mussel shoots her babies out into the water and they dash to latch onto the fish’s gills where they’ll spend the rest of their early childhood.  After several weeks their small shells are formed and they drop off the host fish into the water and float down to the bottom of the stream where they will spend the rest of their lives.

FIELD WORK:

Before the class donned goggles and snorkels, I suggested some things they might look for underwater:

  1.  They could assess the turbidity (cloudiness) of the water by checking its color.  If the water appeared green or brown, why might that be?  It could indicate the presence of algae or sediment.  Why might these be present?  An algae bloom brought on by favorable weather/water conditions might account for an excessive tint, while sediment could be caused by recent rains, erosion, or even watercraft activity upstream.
  2. They could observe the substrate (bottom of the stream).  Were there rocks?  Were they clean?  Are they covered with silt or sand (upstream disturbance or erosion), slime (algae), or a mixture of both?  Were there any plants growing in the water?  If so, what kind?

WRAP-UP:

After exploring the underwater habitat, we gathered to share observations and record these in our nature journals.  I’ll share some of those entries with you soon, and hopefully some of my students (or their moms) will share comments and photos as well.

VIDEOS:

Life Cycle of a Mussel (short)  https://www.youtube.com/watch?v=UD8sHa84M_Q

Mussels Luring Host Fish (mentions evolution)  https://www.youtube.com/watch?v=I0YTBj0WHkU

“Planting” Mussels in the Clinch River  https://www.youtube.com/watch?v=Uf0ZIoNnuiI

BOOKS:

Among the Pond People — Clara D. Pierson (free online)  http://www.mainlesson.com/display.php?author=pierson&book=pond&story=_contents

Wild Folk at the Pond — Carroll Lane Fenton

By Pond and River – Arabella Buckley (free online)  http://www.mainlesson.com/display.php?author=buckley&book=pond&story=life

Pets from the Pond — Margaret Waring Buck

In Ponds and Streams — Margaret Waring Buck

One Small Square: Pond

Pond and Stream – Arthur Ransome (free online)  http://www.gutenberg.org/files/40447/40447-h/40447-h.htm

DK Eyewitness Books: Pond and River

Pond Life (Golden Guides)

 

INTERESTING LINKS:

http://molluskconservation.org/MC_Ftpage.html

http://www.biologicaldiversity.org/campaigns/freshwater_mussels/index.html

http://www.fws.gov/midwest/mussel/harvest.html  (button industry)

 

 

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