Adult Ascaris spp. nematode dissection

Obtain an Ascaris lumbricoides or Ascaris suum worm for dissection. Wear gloves and be careful – these eggs have a small chance of being viable, despite fixation in formalin!

Find the mouth at the anterior end, noting the three lips, one dorsal and two lateroventral.
Affix the worm in a dissecting pan dorsal side up by piercing with a pin near the anterior end. Carefully slit open the body from the anterior working posterior, pinning down the flaps of the cuticle as you go. Observe the body cavity and the hydrostatic pressure that would exist in a live worm.
Observe the different regions of the alimentary canal: an esophagus, a muscular pharynx, a simple flat intestine, and the position along the body where the anus exits.
In a female specimen, the vulva is situated midventrally and about one third down from the anterior end of the worm. The vagina is a short tube connecting the vulva to the bifurcated uterus. The two branches of the uterus coil posteriorly and then anteriorly, becoming oviduct along the way. The ovary lies at the terminal end, where the oviduct is coiled and fine. Eggs simply move along the oviduct and end up in the uterus, where they can be fertilized by the male.
In a male specimen, there is a single testis, a long, fine, tightly coiled tube that is continuous posteriorly with a wider tube, the seminal vesicle. The latter organ leads into a short, muscular ejaculatory duct, which opens into the cloaca. Two spicules arise in pouches of the cloaca and may be seen projecting from the anus.
Be sure to observe the morphology of both sexes: examine a neighbor’s specimen. When finished, please dispose of all tissues in the designated trash. Wash equipment and hands thoroughly with soap. Bleach surfaces.

mealworm

BYOH (bring your own host)!

Nematodes that infect invertebrate hosts are extremely common. Some species occur as simple intestinal dwellers and others are parasitoids. Parasitoids develop inside the host's body and ultimately kill the host. You will be responsible for bringing your own invertebrate host to lab for dissection. This should be a terrestrial insect or crustacean - not an earthworm (which, as you might remember from your invertebrate biology class, is an oligochaete), not a spider (an arachnid), and nothing from a marine environment (marine invertebrates are regulated and can't be collected for science without a permit). In our neck of the woods, your best bet is to poke around in some leaf litter or wood chips to find pill bugs (isopod crustaceans sometimes called roly-polys), which often have mermithid nematodes. If you can get your hands on a cockroach, these are a good source of pin worms. Flies, moths, and beetles will also work. Please don't bring in anything that can bite or sting (e.g., bees, wasps, earwigs). Your host should be transported alive, inside a container. Feel free to bring more than one as that will increase your likelihood of finding nematodes inside.

Select one individual from your container. Don't forget your PPE!
Sever the head to humanely kill the host. If your host is fast (e.g., cockroaches), remove all of the legs, as many can run around even after decapitation.
Place the host's body in a glass dish with some insect Ringers' solution.
Then, slice the body open longitudinally.
Examine the viscera and the body cavity under the stereomicroscope.
If your host is infected, you should see tiny worms moving in the Ringers' solution (see photos and video below to get a search image).
Examine the body cavity of the host and any nematodes you find under the scope.
Remember to write out your experimental protocol, record the infection details for each host you dissect (i.e., host species, where you obtained it, dates of collection and dissection), and draw what you observe in your lab notebook.
Repeat with all the hosts you brought in. You might see different kinds of nematodes in different host individuals, so make sure to keep careful notes of your observations.
If you don't find any nematodes in your host, be sure to look over the shoulder of a neighbor and draw the nematodes they have discovered.