The Intestines of the Earth

Despite most of us paying little more attention to them than a quick pirouette to avoid smooshing them as they crawl on the sidewalk after a spring rain, earthworms happen to be one of the most important soil dwelling invertebrates. In fact, they’re so important that the last scientific book that Charles Darwin ever wrote was about earthworms. So, I invite you on a journey into the soil’s depths, as we get a brief glimpse into the life of Squirmin’ Herman the red wiggler worm (http://extension.illinois.edu/worms/).

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Red wiggler worm. Look at its shiny, mucus-coated skin! Image from: https://www.groworganic.com/redworms-eisenia-foetida-800-1200-lb.html

Red wigglers are a non-burrowing species of worm. They live in the top layer of soil where their primary food source, organic matter, is abundant. A red wiggler can eat around 2 times its weight in organic matter every day! On top of this, they have huge water requirements. Water is constantly secreted through their skin as a slimy mucus. This keeps their body surface moist, so that they can crawl smoothly through the soil. Their moist skin also helps them absorb oxygen and get rid of carbon dioxide, as like other earthworms, red wiggler worms breathe through their skin!

Given these high organic matter and high moisture requirements, I conducted an experiment to test how they would prioritize these two factors. That is, when given a choice between dry soil that is rich in organic matter but lacks moisture, and wet sand that is rich in moisture but lacks organic matter, which would they choose? I was quite surprised to find that a huge majority of the red wigglers I tested, around 90%, chose the dry soil.

I wondered if there was a reason they might have avoided the wet sand. Perhaps it was because, like us, red wiggler worms can sense and respond to unpleasant stimuli, and might have avoided crawling through the sand as it may have been quite scratchy and painful compared to the fluffy soil. Or, since red wigglers aren’t physically adapted to burrow, they may have been unable to crawl into the dense, wet sand, even if they might have preferred to.

I also wondered how they might cope with the dryness of the soil. I learned that almost all earthworm species can tolerate low moisture conditions through a period of inactivity known as aestivation. Some species dig deep into the soil, and tie themselves into a knot in a mucus-lined chamber to minimize water loss. Others keep their body extended, but stop all activity until conditions are more favourable. As for Squirmin’ Herman, in this experiment it seems he and his friends chose the latter option (pictured below on the right).

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Earthworm in knot in “aestivation chamber” during drought conditions. Image from: http://www.arkive.org/earthworm/lumbricus-terrestris/image-A22318.html

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Red wiggler worms extended in dry soil in a choice experiment with dry soil and wet sand. Image taken by Brent Ludwig

 

 

 

 

 

 

 

 

 

 

With that, this brief earthworm journey comes to an abrupt close. However, there are many more earthworm adventures waiting for you outside. Next time it rains, perhaps instead of dodging them, lean in to take a closer look. These underappreciated sidewalk noodles will be pleased to find a friend.

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The Rocky Intertidal Zone: Nature’s Krabby Patty

As we embrace the “SpongeBob SquarePants” theme that our blog site has recently been blessed with, I invite you on an exciting journey to get a taste of Nature’s Krabby Patty: the rocky intertidal zone at Aguilar Point on Vancouver Island’s Pacific coastline. Although it may lack the familiar ingredients (a frozen hamburger, fresh lettuce, crisp onions, tomatoes, sea cheese, pickles, mustard, ketchup, and a secret formula), all of the excitement is preserved in Nature’s Krabby Patty, as it layered with some of the highest diversity found in any ecosystem around the world!

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Pedal disk of the anemone Conostichus ornatus. Image from  http://www.clastics.com/cono stichus.htm

We begin our journey at the burger’s bottom bun closest to the ocean: the low tide zone, containing the most life of all zones within the rocky intertidal ecosystem. This zone is not often exposed to air, so organisms here must be well suited to withstand the intense forces of waves, and are generally not well adapted to air exposure. For example, in our survey of this zone, we found large invertebrates such as the giant green anemone, which maintain a firm grip onto the rocks with a pedal disk, and extend stinging tentacles into the water to capture and immobilize passing prey.

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Blue mussels anchored to rocks with byssal threads. Image from https://phys.org/news/2013-03-blue-mussels-rocky-shores.html

Next, as we ascend into the Patty’s filling, we enter the mid tide zone. Here, organisms must still be well adapted to withstand wave forces, but must also be able to survive more prolonged air exposure. For that reason, in this zone we found mussel beds providing habitat for many other invertebrate species. As the tide recedes, the mussels are able to seal their shells tightly to prevent becoming dried out. Additionally, they secure themselves firmly to the rocks (and to each other) using byssal threads, to prevent being displaced by the waves.

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A chiton sealed to a rock. Image from http://www.democraticunder ground.com/122843600

Finally we reach the top bun, and find the high tide zone. Life here spends a majority of its time exposed to air, and therefore must be very well adapted to prolonged dry periods. As such, in the high tide zone we found black turban snails, chitons, and limpets resisting drying out with their shells sealed completely to rocks.

As we conclude our journey together, we have discovered a just a taste of the diversity of strategies that organisms use to survive the harsh conditions of the rocky intertidal zone. If you have the opportunity, indulge yourself and take a trip to a local shoreline, where if you look closely you will be able to explore countless other strategies organisms use to survive in different intertidal ecosystems. To further wet your appetite, visit the CRD website to learn more about intertidal zones and their inhabitants, why intertidal zones are important, and what you can do to protect them! (https://www.crd.bc.ca/education/our-environment/ecosystems/coastal-marine/intertidal-zone)

 

 

 

 

2 foolproof ways to get rid of your unwanted woodlice roommates!

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Woodlice on a log. Image by http://www.strathearnpestcontrol.co.uk/

Is your home infested with colonies of uninvited, armoured bugs? It may be a breeding ground for terrestrial crustacea known as woodlice (pictured at the right), who are close relatives to shrimp! Luckily, undergraduate researchers at the University of British Columbia have your back, and are finding ways to make your home a less desirable settlement for these pesky critters.

Full disclosure: unless you are an avid collector of rotting wood and other decaying organic matter (a woodlouse’s food of choice), it is unlikely that you are under the immediate threat of such an infestation. However, you can never be too prepared, so I highly recommend that you continue reading.

The student researchers did a series of experiments designed to determine processes that may give rise to the fact that terrestrial isopods tend to be more abundant under logs than on top, using a particular species of woodlice known scientifically as Oniscus asellus (and non-scientifically as Creepy crawlies).

In the first experiment, the woodlice were given a choice between two habitats, one that was dark and another that was well lit. The researchers found that, unlike the monsters inside your closet, woodlice do not disappear when the lights are turned on, as they showed no preference for either the dark or the well lit environment.

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Gills on pleon. Image by http://140.247.96.247/

In the second experiment, they were given a choice between a moist and a dry habitat. This time, the woodlice preferred the moist environment. This made sense as woodlice use modified gills (found on modified hind legs, pictured at the left) known as branched “air trees” to breathe, and like gills, if these are not kept moist, they will be unable to breathe (visit the Slater Museum of National History website for more about these “air trees” and other cool woodlouse biology!: http://www.pugetsound.edu/academics/academic-resources/slater-museum/exhibits/terrestrial-panel/common-woodlouse/).

In the third and final experiment, the woodlice were given a choice between a warm habitat, and a cool habitat, where they showed a preference for the cooler habitat. These are some cool bugs.

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Angry Oniscus asellus with bindle. Edited from image by http://www.uniprot.org/

So what does this mean for you, future and/or current woodlouse infestee? If you want to rid your home of these crawling crustaceans you have 2 foolproof options: (1) turn the humidifier way down and (2) turn the heat way up (make sure you sweat, just not enough to leave moist puddles behind as this will be counteractive). After this, you can be 100% confident that you will be uncomfortably hot, dry, and sweaty, 95% confident that your woodlice roommates will prefer to go somewhere else, and before you know it your home may or may not be woodlouse-free!

Once you have finally evicted your unwelcome housemates, you may find that they have taken over your garden. Do not fret! They will have a happy home here, and will help your garden flourish as some woodlice have been found to control garden pests like stink bugs (https://www.ucdavis.edu/news/humble-roly-poly-bug-thwarts-stink-bugs-farms-gardens) and they are also known to be helpful composters (https://www.rhs.org.uk/advice/profile?PID=723)!