Answer to the Parasite Case of the Week 703: Male Ascaris lumbricoides
As noted by Florida Fan, Dwight Ferris, and several others on Twitter and LinkedIn, we can tell that this is a male because of its curved tail. You can also see the characteristic mouthparts with 3 fleshy lips on the anterior end (if you zoom in quite a bit):
Note that this is a freshly-passed specimen, and fresh specimens may have a red-pink color. Given the color and size, this specimen may also be mistaken for an earthworm. Sam noted that the current specimen "can be differentiated from an earthworm as it lacks a clitellum (which is seen in earthworms in a reproductive state). Also the mouth parts of Ascaris and earthworms widely differ, which can be observed under a microscope."
Thanks again to Idzi for this outstanding case!