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Category: Summer

Out & About: Minnows

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RIDDLE:                Alive without breath, as cold as death, clad in mail never clinking, never thirsty, ever drinking.  (A FISH)

Bilbo Baggins didn’t stump Gollum with that riddle deep under the Misty Mountains, and I couldn’t stump my students with it either!  To focus on fish, our nature study class met beside Little Limestone Creek at Mill Spring Park in beautiful, historic Jonesborough, Tennessee.  It was a warm, overcast day, but the thunderstorms held off and at least the moms were able to stay relatively dry.  The kids were another story — as you will see!  We started off by collecting specimens from the creek in large, clear containers:  Minnows, aquatic insects and even a crayfish.  We brought them to the gazebo, spread out the quilts, got out our hand lenses, and sat down for a good, close look.

 

FIELD WORK:

  • How many fins has the fish?
  • Are the fins constantly moving? Do they move together or alternately?  How is each fin used?  How are they used when the fish swims backward? What are the fins doing when the fish is at rest?
  • Is the tail square, rounded, or notched?
  • What covers the fish? Are the scales large or small?  In what direction do they seem to overlap?  Of what use to the fish is this scaly covering?
  • Can you find a long line running down the fish’s side? That’s called the lateral line.
  • Describe the pupil and iris of the fish’s eyes. Can the fish see in all directions?   Does it do so by moving its eye or its body?  Does the fish wink?  Can you see that the eye is spherical?
  • Can you see the nostrils? Is there a little wart-like sac connected to the nostril?
  • What sort of teeth does the fish have?
  • Does the gill cover move with the opening of the mouth?

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OBJECT LESSON:

The fish usually has 7 fins, which play a different role in the fish’s movements:

Dorsal Fin – like a fan, protects the fish against rolling and assists in sudden turns and stops

Tail (Caudal) Fin — propels the body through the water like a scull

Anal Fin – used to keep the fish stable in the water

Ventral (Pelvic) Fins (2) – The pelvic fins assist the fish in going up or down through the water, turning sharply, and stopping quickly

Pectoral Fins (2) – help fish rise or sink in the water

Sight — The eyes of fish have no eyelid.  Fish are nearsighted because the lens is spherical which enables the fish to see underwater.

Smell — The fish’s sense of smell is located in a little sac to which the nostril leads, but the nostrils have no connection whatever with breathing.

Taste — The tongue of the fish is very bony or gristly and immovable, and they have very little sense of taste.  A fish’s teeth can be located on the jaws, inside the mouth, on the tongue and even in the throat!  Fish without teeth expand their jaws and create a huge vacuum so they can literally inhale their food 😉  Check this out!

Hearing — Fish have poor hearing.  They have only an inner ear and it has no exterior outlet.  Instead, it is found inside the fish’s head behind the eye.  Since fish have approximately the same density as water, sound passes right through their bodies.  That doesn’t mean they don’t respond to auditory stimuli, though.  Recent research indicates that fish may exhibit the Lombard Effect when exposed to loud or unfamiliar sounds.  (The Lombard Effect is the involuntary tendency of speakers to increase their vocal effort when speaking in loud noise to enhance the audibility of their voices.)  You read that right:  Fish communicate out loud.  Here’s a short video of minnows “growling” and “knocking”:

Touch – A fish’s “lateral line” consists of different scales that extend along the sides of the body containing small tubes connecting with nerves; it is used to detect motion and vibration in the water – like touch at a distance.  This lateral line is especially important when fish need to gather and/or travel in “schools” because it allows each fish to sense the motions of its neighbors.

The shape, number and position of a fish’s teeth vary according to the food habits of the fish.  Some have blunt teeth suitable for crushing shells; others  have sharp teeth with serrated edges for harvesting vegetables, while some have incisor-like teeth who feed on crabs and snails.  In some species there are several types of teeth, while others (goldfish and minnows) have no teeth at all.  Fish teeth can be on the jaws but also in the roof of the mouth, on the tongue and in the throat.

The covering of fishes varies:  Some have scales, others have a smooth skin.  All fish are covered with a slimy substance which somewhat reduces friction as they swim through the water.

In order to understand how a fish breathes, we must examine its gills.  They are filled with tiny blood vessels, and as the water passes over them, the impurities of the blood pass out through the thin skin of the gills and the life-giving oxygen passes in.  A fish constantly opens and closes its mouth to draw water into the throat and force it out over the gills – the act of breathing.  Fish can’t make use of the air unless it contains enough oxygen, so it’s important that the water they’re in have enough surface area (definitely NOT like Dr. Seuss’s McElligot’s Pool!)  McElligots Pool 2

 

MAKING OBSERVATIONS:

I’ve been so pleased with the progress of our students in just a few short weeks!  They’re paying closer attention and  noticing so much more.   Maybe these nature observation prompts we’ve been using (from John Muir Laws http://www.johnmuirlaws.com/natural-history/deep-observation) have helped played a role.  For each journal entry they are asked to complete these thoughts:

I notice ______________.  (Example: …this flower has five petals, red anthers and serrated leaves.)  Requires close attention.

I wonder _____________.  (Example: …how it disperses its seeds?)  You can help them follow up with this.

It reminds me of ________.  (Example: …the wild strawberries we saw growing by our boat dock.)  This will eventually lead to classifying specimens by leaf shape, color, and other physical characteristics.  It can also help us make connections to previous learning — a poem, story, work of art.

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My 12yo son’s journal entry this week included a sketch and these observations:
I notice that this tree has shallow roots and the roots are in the creek.
I wonder why the bark is in vertical patterns?  Maybe so rain water will run down to the roots?
It reminds me of elves.  ( He’s a huge Lord of the Rings fan!)

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It’s so important to take a moment to make a short sketch or note a small detail while you’re in the field.  If you goal is a lovely nature journal page you can always flesh things out in living color later.  But that tinge of blue on the tip of a wing or the dew drops collecting on an upturned leaf — those lovely bits may be forgotten if you don’t note them as  you see/hear/smell them.

I’ll leave you with image of a single Cardinal Flower (Lobelia cardinalis) we found growing by the creek and a blue darner damselfly — so very lovely!  (All photos in this post were taken by the lovely and talented Beth Waugh.)

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Out & About: Crayfish

crayfishCrayfish and salamanders and Hickory Horned Devils — OH MY!  What a time we had today at our weekly Nature Study class!  We visited a mountain stream at the  foot of Bays Mountain in Kingsport, Tennessee to learn about crayfish.  But we learned about so. much. more.

OBJECT LESSON:

The greatest diversity of crayfish species is found in southeastern North America, especially Appalachia (that’s us), with over 330 species.

Crayfish are detritivores (they eat detritus = decomposing plant and animal parts) but they also eat living plants and animals such as worms and insects. Raccoons, snakes, opossums and muskrats are the crayfish’s most dangerous predators.

The crayfish breathe through feather-like gills and tend to inhabit water bodies that don’t freeze all the way through to the bottom. Some species are found in brooks and streams where there is fresh water running, while others thrive in ponds, swamps and ditches. Most crayfish cannot tolerate polluted water, so if they are present the water is probably pretty clean.

Crayfish burrow during the late summer, and spend most of the fall and winter underground in water-filled tunnels. Everywhere you see a crawfish chimney, there is a crawfish living in a burrow underneath. Their tunnels may extend down into the earth 3 feet or more and are full of water. Sometimes the color and texture of the chimney mud is different at different levels of the chimney. Why might this be? This is a sign that there are different types of soil layers below the surface, and the crayfish has burrowed through several layers.

As the crawfish burrows down, it brings up soil from different layers and deposits the pellets of mud at the top of the chimney.  https://www.youtube.com/watch?v=DSIY5oUaUr4

During droughts, crayfish routinely plug the openings of their burrows with mud. As the water table drops, or when the temperature drops, the animal moves further down to warmer water levels. Over time, oxygen may be depleted in the burrow water. When this happens, the crayfish may position itself just above the water, thus keeping the gills wet and absorbing oxygen from the air in the burrow.

Crayfish also lay eggs in their burrows. After they mate in open water, (the male depositing sperm into a special sac on the female’s abdomen) the female (and sometimes the male as well) will dig a burrow where the female will lay the eggs, fertilize them with the stored sperm, and hold them attached to little appendages under the tail called swimmerets.

Once the eggs are laid, the male typically stays near the entrance and the female remains deeper in the burrow. As long as oxygen levels in the burrow water are high, the female keeps the eggs under water and swishes them back and forth to ensure aeration (air circulation). As the oxygen drops, the female keeps the eggs moist, but gets them out of the water, thus allowing them to absorb oxygen from the air. https://www.youtube.com/watch?v=XHCWiISnu_4

The eggs usually hatch in the burrows and begin to grow. Since there is a restricted amount of food available in the burrow, the babies eat infertile eggs and the bodies of dead babies. They will even kill each other to survive.

https://www.youtube.com/watch?v=F1IhRReU4I4

After the hatching, with her brood still attached, the female emerges from the burrow to find food. Once she is in open water, the hatchlings detach from their mother and begin living independently.

A young crayfish molts 11 times before becoming an adult. This takes about a year. They will live another year to mate and produce young. In this video, the carapace (shell) completely detaches about 5 minutes in: https://www.youtube.com/watch?v=mF6NgMBcNCM

In 2011 a new species of giant crayfish was discovered in Shoal Creek, a tributary of the Tennessee River.  “A new species of giant crayfish [has] literally crawled out from under a rock in Tennessee, proving that large new species of animals can be found in highly populated and well-explored places,” Reuters reported. Aquatic biologists had been studying life in that little waterway for decades, but it appears these crayfish are not common (only 5 have ever been caught) and their preference for living under large rocks in deep water may have made them easy to overlook, especially in times of high water. After DNA testing and studying a ridge and unique spine between the crayfish’s eyes, the biologists knew they were looking at something entirely new, and named it Barbicambarus simmonsi (after TVA scientist Jeffrey Simmons — the guy who first spotted this giant).

Here’s a video about the discovery which gives some interesting insight into how these creatures are measured and catalogued.  https://www.youtube.com/watch?v=e05nqc1ygYg

FIELD WORK:

We spread out along the length of the creek.  We haven’t had much rain lately so the water was low.  Within 15 minutes the class had collected about 30 samples of crayfish at all different stages of development and a couple of baby salamanders.

Then a shout went up:  Look what was found crawling along on the creek bank!

hickory horned devil

 

 

 

 

It’s a Hickory Horned Devil Caterpillar that will dig a hole in the ground and after pupating through two winters will emerge as a beautiful, huge Royal Walnut Moth!

 

And if that’s not enough, look who else came to call:

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mantis

Out & About: Freshwater Jellyfish

freshwater jellyfishDid you know there are JELLYFISH in Bays Mountain Lake?  Today our Nature Study class visited Bays Mountain in Kingsport, Tennessee, to learn about freshwater jellyfish.  We even convinced a good-natured naturalist to take us on a barge ride around the lake to investigate!  How in the world did they get there, you ask?  Read on…..

OBJECT LESSON:

Although we call them freshwater jellyfish, some argue that the Craspedacusta sowerbii is more closely related to the Hydra family than a “true” jellyfish, so many naturalists and scientists just call them Freshwater Jellies.  The main difference between jellies and “true” jellyfish is the presence of a velum — a think circular membrane around the cap that helps propel the jelly forward.  Freshwater jellies are transparent, gelatinous, umbrella-shaped creatures with a whorl of stringy tentacles around the edge of their bodies.  Microscopic barbs called nematocysts run along the tentacles to help capture food and protect the jelly from predators.  Luckily for us, jellies are quite small — adults are the size of a quarter — and their stings can’t even penetrate our skin.

Jellies have no head or skeleton, and contain no special organs for respiration or excretion.  Their bodies are 99% water.  Their large, flat reproductive organs are the only parts of the freshwater jelly that are not translucent, and this makes them easy to spot on sunny days when they tend to surface in large groups called “blooms.”  They eat tiny microscopic animals called zooplankton that are found floating in the water.  When they come into contact with prey, stinging cells in the jelly’s tentacles paralyze the organisms and then sway about moving the captured prey its mouth which is in the middle of the underside.  The bell (body or umbrella part) of the jelly goes through several contractions to move the prey into the mouth and digestive cavity.  The primary predators of freshwater jellies are crayfish and turtles.

Freshwater jellies have a multi-stage life cycle that includes two forms — the polyp and the medusa.  The medusa form is more familiar, and it is during this adult stage that jellies reproduce sexually and fertilized eggs that develop into larvae detach from the medusa and drift away.  This larvae form, now called polyps, will also reproduce — but it will do so asexually by dividing from one another.  This is called “budding,” and the buds will then develop into adult medusa and the cycle repeats.  During the winter the polyps contract and become “resting bodies” that are capable of surviving the cold temperatures.  They are circular and fairly flat with no hooks or burrs, but there does seem to be some adhesive property which allows them to become attached to surfaces.  Some scientists believe that the resting bodies are one way in which the jellyfish are transported — on aquatic plants, by aquatic animals, or on the feet of birds.  When conditions become favorable and temperatures rise, the resting bodies develop into polyps and the life cycle continues.

Freshwater jellyfish can be found all over the world, but are not native to the United States.  There are two schools of thought on their origins.  Some believe they originated in the upper Yangtze River basin in China, and were first observed in the western world in water lily ponds in London’s Regents Park in the late 1800’s — having presumably arrived as polyps on the plants imported from China.  Others say they originated in South America and made their way to the US in the bilge water of ships.  However they got here, jellies spread rapidly and are now found all over the US in every state except North and South Dakota, Montana, Wyoming, Alaska and Hawaii.  Why might this be?  (Too cold in most of these places, and Hawaii just doesn’t have enough fresh water)

I asked the class how jellies might have gotten into Bays Mountain Lake.  They can enter a body of water in many ways — in the water of bait buckets, through flooding from another site, on boat propellers.  But we decided the most probable answer may be that they were carried in on the feet of migrating birds during the “resting body” stage of development.

The appearance of jellies is sporadic and unpredictable.  Often they will appear in a body of water in large numbers even though they were never reported there before.  The following year they may be absent and may not reappear for several years.  It’s also possible for jellies to appear once and never appear in that body of water again.  In some lakes they appear almost every single year.  Why this difference?  What triggers the appearance of medusa in certain places and at certain times?  Temperature seems to play some role in triggering the medusa stage, which is why there is a freshwater jellyfish season, typically from August to September when water temperatures are highest.

FIELD WORK:

Searching for jellyfish can be a fruitless venture, but the best time of year is NOW, and they are most likely to be found in calm bodies of water, which they prefer to rocky, fast-flowing rivers and streams.  After walking across the dam and peering into the deepest part of the lake (which is what jellies usually prefer) we were unable to locate a single specimen.  So Ranger Bob (sans the ponytail and facial hair he has sported for years) graciously treated us to a long ride on the barge so we could explore further.  While we didn’t encounter any jellies (none of the naturalists we spoke with have seen them this year), we did see beaver dams, water lilies and lots of dragonflies.  Definitely time well spent!

WRAP-UP:

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.

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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.

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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