Date of Award


Degree Type


Degree Name

Master of Science




Biology (MS)

First Advisor/Chairperson

Dr. Alan J. Rebertus


I update the distribution of two cryptic slug species, Arion fuscus and Arion subfuscus, in the Upper Great Lakes of the United States using molecular identification methods. Arion fuscus has not previously been reported in the literature in this region, and Arion subfuscus has previously been reported as abundant. However, all previous distribution studies were determined using visual identification tools, which can result in misidentification between cryptic species. To molecularly re-examine these distribution maps, I used a mitochondrial ribosomal subunit 16S PCR amplification and subsequent SSpI and MfeI restriction enzyme digest to identify slug specimens. I collected slugs in 11 locations around Lake Superior, Lake Michigan, and Lake Huron using beer-baited pitfall traps from May to September of 2022. I collected slugs at one location in Marquette, Michigan biweekly, a total of eight times, throughout the summer to monitor fine-scale slug activity. I found Arion fuscus at 9 of the 11 locations and Arion subfuscus at no locations. Arion fuscus was found early in the spring before other slug species were active. This confirms the inaccuracy of previous distributions determined through visual identification, and calls for the widespread molecular re-examination of current slug distributions.

Access Type

Open Access