Paper Type

Master's Thesis


College of Arts and Sciences

Degree Name

Master of Science in Biology (MS)



NACO controlled Corporate Body

University of North Florida. Department of Biology

First Advisor

Dr. Frank Smith

Second Advisor

Dr. Candice Tahimic

Third Advisor

Dr. David Waddell


Tardigrades have a highly simplified anteroposterior (AP) axis. The mechanisms that regulate the development of this secondarily simplified AP axis are not known. In many animals, the canonical Wnt (cWnt) signaling pathway regulates primary axis establishment through antagonistic interactions with inhibitors of cWnt signaling. This study investigated the roles of shaggy, an inhibitor of cWnt signaling, in regulating development in the tardigrade Hypsibius exemplaris. Gene expression patterns of shaggy and other components of the cWnt signaling pathway were analyzed alongside markers of anterior and posterior identity using Hybridization Chain Reaction in situ in H. exemplaris. RNA interference targeting shaggy resulted in tardigrades with a variety of defects, including anterior defects, elongation defects, AP axis duplications, and everted hindguts. Most of these specimens experienced stalled development at the elongation stage, a stage during which the AP axis normally forms. Additionally, six3, a marker of anterior fate was either lost or reduced while caudal, a marker of posterior identity, was expressed ectopically in some shaggy RNAi specimens. These data may reflect a role of shaggy in regulating AP axis development by regulating anterior fate, a function that is conserved in most other bilaterians investigated. Shaggy RNAi also produced segmentation defects that ranged from minor fusions between segments to the loss of several segments. Shaggy regulates segmentation in insects. Therefore, the segmentation defects recovered in H. exemplaris could represent a conserved segmentation role of shaggy. In summary, shaggy regulates the development of key features of the highly derived tardigrade body plan.

Available for download on Friday, May 02, 2025