An earthworm has a simple anatomy, so dissecting a specimen is not a complicated process. They belong to the annelid phylum, which represents segmented worms. Like most annelids, the internal organs of an earthworm are clearly recognizable. During dissection, you can reveal structures such as the crop, which stores food; the gizzard, where digestion begins; and the clitellum, where reproductive organs are located. Because of the straightforward nature of the dissection, a limited number of tools are required. Primarily, implements are used to hold the specimen in place and reveal the internal organs of the organism. A dissecting microscope is also helpful for examining tissues.
Typical dissection lab tools are needed to prepare the specimen for the procedure. Place the earthworm on a dissecting tray, which can be disposable or reusable. Hold the body of the worm in place with dissection pins. These are sturdy pins, about 1.5 to 2 inches long, with a T head for easy handling. The pins go through the body into the tray, securing the specimen for the next step.
Use forceps to obtain a secure hold when opening the earthworm. Make the initial cut through the skin with sharp dissecting scissors. Make shallow cuts through the skin from one end to the other, opening the worm up. Alternately, a scalpel may be used instead of scissors to cut through the skin.
Latex or nitrile gloves protect hands from contact with the specimen but also keep dirt from hands away from the earthworm. Some individuals choose to wear other protective equipment as well. This gear is optional; it is not typically a part of the basic earthworm dissection process. A lab coat shields clothing from foreign materials. Goggles provide cover for the eyes. During earthworm dissection, most protective paraphernalia is used primarily for cleanliness; it does not impact the procedure.
Take a Good Look
An earthworm’s internal organs can be viewed through a dissecting microscope. This type of microscope allows enhanced observation of objects that are too large for a compound microscope. Because the magnification is low, this microscope cannot be used to examine cells. Instead, it provides clear, three-dimensional images of the earthworm’s internal organs. Specimens do not have to be prepared and mounted on slides; they are viewed in their entirety.
- San Diego Miramar College: Dissection Guide for the Earthworm
- University of California, Irvine: Worm Dissection Activity
- East Stroudsburg University: Kingdom Animalia: Phylum Annelida
- Home Science Tools: Dissecting Tray, Styrofoam
- Home Science Tools: Dissection Pins
- Keene State College: Earthworm Dissection
- Miami University: College of Arts and Sciences: Types of Microscopes
- Hartnell College: Microscopy
- Crescent Public Schools: Earthworm Anatomy
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