Zach is doing a full-year research project (Biol 399) on Chaetogaster worms associated with freshwater snails. Despite being known from several different continents, these snail-riding worms have been placed in a single species, C. limnaei. There are two named subspecies that occupy different parts of the snail (C. l. limnaei on the outside of the snail’s body, C. l. vaghini in the kidney of the snail). Zach is photographing slide-mounted worms to address many questions, including (1) does diet, based on visible gut contents, differ between different sizes of worms? (2) does diet differ depending on family of host snail? (3) does morphology of worms from Canada match the original descriptions of C. l. limnaei and C. l. vaghini from Great Britain? The answers will require analysis of several thousand photos, some of which are shown below.