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iLabs: “Catch of the Day” – The Very Hungry Aeolosoma

August 21, 2014

by Micro World Lab staff member Nancy Locquet-Absillis

Munching away, a very hungry, microscopic worm-like organism slides steadily around in the  murky green algae, trapped between a coverslip and a microscope slide.  It is named Aeolosoma (pronounced e’ o lo so’ ma) and it, like most microscopic creatures in our lab, spends most of its time looking for food.

Aeolosoma feeding on plant debris in culture

Aeolosoma feeding on plant debris in culture.

Can you see why this worm is also known as a bristle worm? Large bristle-like hairs called setae (see-t-A) appear to serve as legs and help the Aeolosoma to move around in its environment.

Most Aeolosoma have been commonly found in artificial ecosystems such as sludge digesters, but ours usually hang out in debris at the bottom of the pond water containers.

Very little is known about Aeolosoma species living in nature. We do know that species living in waste disposal systems are capable of processing large amounts of raw sewage into sludge as they digest decaying organic matter and prey on microorganisms such as bacteria and protozoans.

You could compare this microscopic bristle worm with its relative, the earthworm. Both play an important role as decomposers. By digesting detritus, they break down dead organic matter into smaller pieces allowing bacteria and other organisms to further break it down, releasing nutrients in the process.

Aeolosoma with bristles showing

Aeolosoma with bristles and segments visible.

It’s hard to see, but Aeolosoma have segmented bodies.  Most Aeolosoma have about 17 segments but some species have more. It seems that, apart from the head and the first segment behind the head, each segment has 2 sets of setae at either side of its body.

Because Aeolosoma are so big, it’s easy to spot these “giant” worms at a magnification of 4x (this means that the image seen on the EVOS microscope screen is 65x magnified compared to real life).

If you look closely, you can see red-colored pigments in dot-like structures called globules (gland cells) in the outer layer of cells called epidermis. The function of these colored epidermal gland cells is unknown, but since the color of these gland cells can vary from red to brown, green, blue-green, yellow or colorless, it’s an easy tool to identify species.

Aeolosoma with arrow pointing to mouth

Aeolosoma with arrow pointing to mouth.

Its U-shaped mouth is clearly visible in the picture above; it is located underneath its big, rounded, oval shaped head and acts as a very efficient vacuum cleaner, picking up microscopic plants and microorganisms as it meanders through algae and decaying matter.

Tiny little hairs called cilia on the fringes of its mouth are constantly moving, creating the vacuum effect.

Because of the transparency of the Aeolosoma, you can clearly see how the food particles are being digested, bit by bit. The food particles move through its digestive system by the contraction and relaxation of the muscles until it leaves the 1 to 2 mm long body (peristalsis movement).

Some Aeolosoma are excellent swimmers and move smoothly through clear patches of water under the microscope but most of the time, you’ll see them “snuffeling” for food. With an unstoppable appetite, we just consider them the ever-so-very-hungry Aeolosoma.

An Aeolosoma "vacuuming' food into its mouth

An Aeolosoma “vacuuming” food into its mouth.


One Comment leave one →
  1. goldfire407 permalink
    August 21, 2014 2:37 pm

    Thank you Deb. I Love these.    

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