Microblog Volvox

Our micro-videographer Linda Bower is producing fantastic videos with her microscope at a rate I will never be able to keep up with.  We will start posting her videos with her comments and a listing of their length under the title Microblog.  I plan to write on topics such as cladocera and water bears when I "get around to it."  And don't bother sending me one, I will have to find the time on my own.

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 Volvox birthing 3:50

This Volvox mother colony was found in farm pond water located in the Missouri Ozarks, USA. Guest appearances by Cladocera and a variety of plankton.

New to Volvox? No Linda, Barb and I talk about them every day at breakfast!

Volvox is a genus of some 20 species of freshwater green algae (division Chlorophyta) found worldwide. Volvox form spherical or oval hollow colonies that contain some 500 to 60,000 cells embedded in a gelatinous wall and are often just visible with the naked eye.  Read more here: at Britannica.com's Volvox entry.

Water Fleas

Great fleas have little fleas upon their backs to bite 'em,
And little fleas have lesser fleas, and so ad infinitum. 
                              -Nursery rhyme 

The WOLF school has been exploring life in a few drops of pond water.  While trying to photograph some tiny pond pygmy backswimmers flitting around in a single drop, I came across these indistinct creatures.  I could tell they were alive by the motion in their body in the video, but I could not make out any distinct features with my crude equipment.  I sent the video to Dr. David Bowles who identified them as water fleas of the Cladocera order of crustaceans.

Dorsal view - Click to enlarge

There is nothing to see at first glance to suggest that this is related to the noble order that includes lobsters, shrimp and crayfish.  There are over 600 species plus many more that haven't been identified for reasons I can understand, looking at our specimen.  The first evidence of life I saw was when it defecated in this video.  Be watching carefully at the 20 second mark.

It has a translucent carapace covering all but the small head, showing all the internal organs.  The green dots are eggs, something it produces usually on its own (parthenogenesis) except when under harsh conditions when it reverts to sexual reproduction as described in the Kansas Naturalist.  I can make out its single compound eye, mounted above the beak-like rostrum like a early prototype of a Cyclops.

From the Kansas Naturalist

Aside from its monocular vision, water fleas have several other interesting features.  It has two pair of antennae, the first having tiny olfactory hairs.  The second pair are well muscled and are used for swimming, its sole method of propulsion.  Its legs are covered with fine hairs which strain food particles such as phytoplankton, bacteria and organic detritus. 

As a herbivore, water fleas are at the very base of the food chain, the first consumers as well as some of the smallest prey of the tiny pygmy back swimmers we have been studying.  ..... and so ad infinitum.

Aquatic Worms

While collecting pond water to feed some damselfly larvae I came across some of these transparent worms.  They slither around in the decaying leaves like earthworms, and indeed they are in the same family, Oligochaete.  They are found in almost any freshwater pond, preferring the shallow areas either on top of sediment or deeper into it. 

They avoid bright light which they detect with primitive photoreceptors all over their body.  Movement is almost peristaltic and each segment has chaetae, bristles with muscles, so they can pull them in or extend them to grip the mud or simply swim as seen in this video.

Some Oligochaetes are predatory, feeding on other worms and tiny crustaceans such as cladocera (water fleas), while others eat detritus such as decomposing organisms and bacteria.  They eat by extending their pharynx like a tongue, in some cases even turning it inside out like a suction cup to pull food into their gut.

Planaria - Click to enlarge

Most reproduction is asexual.  They can split in half or even multiple pieces, each then regenerating into a full worm similar to the planaria we have been finding this winter.  Another mechanism is producing buds where new worms grow out of their body before separating as  new individuals.

Sexual reproduction is a mutual act with flexibility as they are hermaphrodites, each having male and female parts.  One may fertilize the other or they may fertilize each other at the same time.  The egg and sperm form a cocoon which is deposited in the pond bottom where they will emerge shortly or overwinter to come out in the spring.  If the pond dries up they can survive for a while as cysts.

This shallow pond is 150 feet above the creek valley and a quarter mile from other ponds.  In spite of this it is teeming with life, likely brought in on the feet of wood ducks which visit frequently.  Oligochaetes are close to the bottom of the food chain.  They are spared predators like fish and crayfish but have to dodge newts, salamanders, frogs and even tadpoles.

Coming soon, more strange pond life.