Phylum Annelida: They Ate Your Crap and They’ll Eat You Too
Deducing the Organism
As per usual, I fell for Dr. McCluney’s tricky organism selection and concluded that the mystery organism this week was a cephalopod of phylum Mollusca. The organism had multiple arms, and even appeared to have the two differentiated tentacles characteristic of squid. My partner found that the organism was a deep-sea annelid instead, and upon further inspection of what I thought to be the mantle of a squid, I realized it was a segmented body; a defining characteristic of the annelids.
Double, Double, Soil and Rubble
A common earthworm moving through underbrush Source: https://commons.wikimedia.org/wiki/File:20060131_earthworm_hits_dirt.jpg
One of the key services to humans from annelids comes from class Oligochaete that inhabits almost every continent. Earthworms are critical to breaking down organic matter in soil into nutrients for plant life. Studies in New Zealand have shown that soil with earthworms in it yields up to 70% more crops, and the crops were healthier as well (How earthworms can help your soil, 1970, January 01). Earthworms also are vital to maintaining soil stability and preventing soil erosion. Along with this, they increase soil drainage as well, allowing ideal conditions for plant growth.
We Didn’t Start the Fire(worms)
A hunting bobbit worm Source: https://en.wikipedia.org/wiki/Eunicida#/media/ File:Eunice_aphroditois.jpg
Annelids that have benefits and drawbacks to humans are Bearded Fireworms (Hermodice carunculata), and other types of worms in the class Polychaete. These worms sneak into aquariums on pieces of rock collected directly from the sea. The worms can lie dormant in dried rock for weeks, and once the rock is placed into an aquarium, the worm can live off of detritus while it grows. As long as the worms are small and few, they can be an indicator of a healthy aquarium being fed proper amounts. If the worms grow too big and begin to reproduce, it means an aquarium is being overfed and the worms can eventually begin eating fish (Bad Types Bristleworms & Fireworm Control in Saltwater Aquariums n.d.). These Polychaete can grow to be up to 9 feet long, and once they reach a certain length, almost all fish in a tank are at risk. For a video of a giant bristle worm, click here.
Leeches: They Suck
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A tiger leech attached to a human finger Source: https://commons.wikimedia.org/wiki/File:Haemadipsa_picta,_the_Tiger_Leech_(13177093114).jpg
An annelid that does not benefit humans is almost every member of class Hirudenea, i.e. leeches. Leeches are annelids that consume small vertebrates, insects, mollusks, and mammalian blood. As can be expected, this poses multiple problems for humans. Juvenile leeches eat the larvae of multiple organisms important to wetland ecosystems such as frogs, salamanders, snails, mayflies, and dragonflies. Leeches, like mosquitos, also transmit blood-born pathogens to humans through their feeding behaviors. In the 1800’s, it was widely believed that disease was the result of excess blood, so leeches were used for blood drainage. The chemical Hirudin is secreted by feeding leeches, and this keeps blood from coagulating. Leeches are almost completely painless as well, so they likely have a natural anesthetic as well (Ricarimpex Leeches medicinalis, n.d.). Leeches are still used in medicine, but only for bloodletting (Modern Leeching, n.d.). Leeches also are known to consume the aforementioned earthworms, reducing their presence in ecosystems. For a video of a leech eating a worm, click here.
Works Cited
Bad Type Bristleworms & Fireworm Control in Saltwater Aquariums. (n.d.).
How earthworms can help your soil. (1970, January 01).
Modern Leeching. (n.d.).
Ricarimpex Leeches medicinalis. (n.d.).