Paper Type

Master's Thesis


College of Arts and Sciences

Degree Name

Master of Arts in Biology (MA)



NACO controlled Corporate Body

University of North Florida. Department of Biology

First Advisor

Dr. Frank Smith

Second Advisor

Dr. David Waddell

Third Advisor

Dr. Marie Mooney

Department Chair

Cliff Ross

College Dean

Kaveri Subrahmanyam


Segmentation has facilitated the evolution of the many forms of the panarthropods. Downstream regulation of segmentation is controlled by the highly conserved segment polarity network which includes the genes engrailed (en), hedgehog (hh), wingless (wg), cubitus interruptus (ci), patched (ptc), and smoothend (smo). While a high level of conservation has been seen in both the arthropods and onychophorans, only en has been described in any representatives of Tardigrada. Previous work had already established the loss of wg, which encodes for a Wnt ligand, in the tardigrade H. exemplaris. However, two other Wnt genes -Wnt4 and Wnt16B- were identified in H. exemplaris that could have a segment polarity function . To investigate segmentation in tardigrades we analyzed the patterns of the genes engrailed (en), hedgehog (hh), cubitus interruptus (ci), patched (ptc), smoothened (smo), Wnt4 and Wnt16B in H. exemplaris using Hybridization chain reaction (HCR) in situ. Only en was expressed in a repeated pattern before segments were present. En and ci were expressed in a segmental pattern after segment boundaries are present, and en, hh, and ci were also expressed in the developing limbs. Ptc was most strongly expressed in the cells at the anterior and posterior trunk boundaries, and later ubiquitously at the limb bud stage. Smo expression was not seen. Wnt4 and Wnt16B were not expressed like wg is expressed in other panarthropods. We conclude that features of the segment polarity network are conserved in Tardigrada, and that En, Ci, and Hh may help pattern segments and appendages in tardigrades. We also conclude that the cells secreting and receiving the signals of the Hh and Wnt pathways to pattern each segment in other panarthropods are not conserved in Tardigrada.

Available for download on Thursday, January 16, 2025