Crustaceans In a Rotting Tree Stump - ...and, What is a Crustacean Anyway?

When we think of crustacean we might think of crabs, lobsters, prawns, and shrimps. But there are many terrestrial crustaceans as well. In fact there are probably many in your backyard. I came across plenty of them in an old decomposing tree stump in my backyard this afternoon. I took the opportunity to takes some photos including this one :

_{( All photos, videos, and text on this blog are by @mostly.nature )}

_{An Isopod Crustacean known as a Slater}

I grew up calling them slaters but of course there are dozens of names for these around the world. Some other English language names include Rolly polly, Woodlouse, Sowbug and Pill bug. Please let me know in the comments what they are called where you are.

So, what makes them a Crustacean?

Well first up, the animal kingdom is divided up in to various broad divisions known as phylums. The phylum Arthropoda includes animals with a hard exoskeleton and jointed limbs. This includes spiders, insects, crustaceans etc. Within the Arthropods are various sub-phylums. Crustacea is one such sub-phylum. One of the unique attributes of Custaceans is that they have, at least some, biramous appendages. That is to say that some of the appendages are branched (like little appendages coming off larger appendages ). Coming further down the taxonomic hierarchy we come to a group known as Isopoda which includes slaters. Slaters and other Isopods have five pairs of flattened biramous appendages on their abdomen which serve the function of lungs (or gills in the case of aquatic species).

There are likely other species of crustaceans living in your yard too. For example, Landhoppers. At the same rotting stump in my yard, there is a layer of decayed wood (like saw dust) on the ground. Brushing it aside with my fingers revealed dozens of tiny Landhoppers. These things can jump many many times there own body length. When disturbed they all start jumping about and wriggle their way back below the surface. Within seconds they have vanished from sight. While our Slaters belonged to an Order known as Isopoda, the Landhoppers belong to the Amphipoda. The ones in the photos below are quite tiny at around 3mm- 3.5mm in length.

_{A Lanhopper. This one belongs to the family Talitridae}

_{Another view of the same Lanhopper.}

Getting away from the subject of Crustaceans, I've also included two other creatures that were also in my rotting tree stump. Together, along with help from a host of other life forms, they have essentially turned the said stump into compost and punk wood in just five years. It's almost completely gone now.

_{A Darkling beetle, Meneristes australis of the Tenebrionidae family.}

_{A Millipede. I don't have an ID for this one yet. Lets just say it belongs to the class Diplopoda}

Further Reading:

• Harvey, Mark S. & Yen Alan L. (1989) Worms to wasps : An illustrated guide to Australia's terrestrial invertebrates - Melbourne : Oxford University Press in association with Museum of Victoria. ISBN: 0195530810 (pbk.)

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