Seth Tyler

Contact Information

Phone: 207.581.2549


Lab website: Link to Website

Address: 203 Murray Hall


Ph.D. University of North Carolina, 1975

Research Interests

Invertebrate biology; electron and fluorescence microscopy; phylogeny of lower invertebrates; meiofauna


Invertebrate biology is the broad area of my research interests, and I concentrate on invertebrates of the meiofauna—that is, small animals living in the interstices of marine sediments, especially the more primitive worms such as acoels and other turbellarians, gnathostomulids, and gastrotrichs. I apply electron microscopy and laser scanning microscopy to these animals, comparing their anatomies in search of clues to phylogenetic relationships among major taxa and clues to the functional morphology of their microorgans. A recent major project centers on phylogenetic relationships of three groups of lower worms: Acoela, Catenulida, and Gnathostomulida. The acoels and gnathostomulids have both served in some theories of animal evolution as the most primitive of the bilaterally symmetrical metazoans (all animals outside of cnidarians and sponges). Through collaboration with Dr. Matt Hooge (UMaine) and Dr. Wolfgang Sterrer (Bermuda Aquarium and Zoo) we have sampled these taxa worldwide and applied information from our detailed morphological studies to hypotheses of phylogenetic relationships that we and other collaborators have generated from DNA-sequence data. The correlations contribute to understanding how key characteristics of these worms evolved and how the animals are related to each other and to the rest of the animal phyla. From such understandings come better means for classifying the animals in formal taxonomy.

As a member of a team of programmers developing a learning-management system, I engage in a form of pedagogical research about how best to apply multimedia in teaching, how to meet a diversity of learning styles among students, and how to gauge progress in achieving learning objectives.


Kolasa, J. and S. Tyler (2009) Flatworms: Turbellarians and Nemertea. In: Thorp, J. H., ed. Ecology and Classification of North American Freshwater Invertebrates. Third Edition. Academic Press.

Achatz, J.G., M.D. Hooge, A. Wallberg, U. Jondelius, and S. Tyler (2009) Revision of acoels with 9+0 sperm ultrastructure (Convolutida) and the influence of sexual conflict on morphology. Journal of Zoological Systematics and Evolutionary Research. (in press)

Egger B., D. Steinke, H. Tarui, K. De Mulder, D. Arendt, G. Borgonie, N. Funayama, R. Gschwent- ner, V. Hartenstein, B. Hobmayer, M. Hooge, M. Hrouda, S. Ishida, C. Kobayashi, G. Kuales, O. Nishimura, D. Pfister, R. Rieger, W. Salvenmoser, J. Smith, U. Technau, S. Tyler, K. Agata, W. Salzburger, and P. Ladurner (2009) To be or not to be a flatworm: The acoel controversy. PLoS ONE 4(5): e5502. doi:10.1371/journal.pone.0005502.

Todt, C., and S. Tyler (2007). Ciliary receptors associated with the mouth and pharynx of Acoela (Acoelomorpha): a comparative ultrastructural study. Acta Zoologica 88:41-58.

Achatz, J., M.D. Hooge, S. Tyler (2007) Convolutidae (Acoela) from Belize. Zootaxa 1479:35-66.

Hooge, M.D., and S. Tyler (2007) Acoela (Acoelomorpha) from Belize. Zootaxa 1479:21-33.

Hooge, M.D., and S. Tyler (2006) Concordance of molecular and morphological data: Example of the Acoela. Integrative and Comparative Biology 46:118-124.

Todt, C., and S. Tyler (2006) Morphology and ultrastructure of the pharynx in Solenofilomorphidae (Acoela). J. Morphology 267:776-792.

Petrov, A., M.D. Hooge, and S. Tyler (2006). Comparative morphology of bursal nozzles in acoels (Acoela, Acoelomorpha). Journal of Morphology 267: 634-648.

Hooge, M.D., and S. Tyler (2005) New tools for resolving phylogenesis: A systematic revision of the Convolutidae (Acoelomorpha, Acoela). J. Zoological Systematics and Evolution Research 43: 100-113

Hooge, M.D., and N. Eppinger (2005) New species of Acoela (Acoelomorpha) from the Gulf of California. Zootaxa 1009: 1-14

Ogunlana MV, Hooge MD, Tekle YI, Benayahu Y, Barneah O, Tyler S (2005) Waminoa brickneri n. sp. (Acoela: Acoelomorpha) associated with corals in the Red Sea. Zootaxa 1008: 1-11

Tyler, S., and M.D. Hooge (2004) Comparative morphology of the body wall of flatworms (Platyhelminthes). Can. J. Zool. 82:193-210.

Petrov, A., M.D. Hooge, and S. Tyler (2004). Ultrastructure of sperm in acoels (Acoela, Platyhelminthes) and its concordance with molecular systematics. Invertebrate Biology 123:183-197

Hooge, M.D., and S. Tyler (2003) Acoels (Platyhelminthes, Acoela) from the Atlantic coast of North America. Meiofauna Marina 12:1-30

Sørensen, M.V., P. Funch, M. Hooge, and S. Tyler (2003) Musculature of Notholca acuminata (Rotifera: Ploima: Brachionidae) revealed by confocal scanning laser microscopy. Invertebrate Biology, 122:223-230.

Tyler, S. (2003) Epithelium—the primary building block for metazoan complexity. Integrative and Comparative Biology 43:55–63.

Gschwentner, R., J. Mueller, P. Ladurner, R.M. Rieger, and S. Tyler (2003) Unique patterns of longitudinal body-wall musculature in the Acoela: The ventral musculature of Convolutriloba longifissura. Zoomorphology 122(2):55-62.

Hooge, M.D., and S. Tyler (2003) Two new acoels (Platyhelminthes, Acoela) from the central coast of California. Zootaxa 131:1-14.

Sørensen, M.V., S. Tyler, M. Hooge, and P. Funch (2003) Organization of the pharyngeal hard parts and musculature in Gnathostomula armata (Gnathostomulida: Gnathostomulidae). Can. J. Zool. 81:1463-1470

Hooge M.D., P.A. Haye, S. Tyler, M.K. Litvaitis, and I. Kornfield. 2002. Molecular systematics of the Acoela (Acoelomorpha, Platyhelminthes) and its concordance with morphology. Molec. Phylog. Evol. 24: 333-342

Pfistermüller, R., and S. Tyler (2002) Spermatozoa and spermatogenesis in Genostoma kozloffi (Plathelminthes, Rhabdocoela). Zoomorphology 121:149–158.

Pfistermüller, R., and Tyler, S. (2002) Correlation of fluorescence and electron microscopy of F-actin-containing sensory cells in the epidermis of Convoluta pulchra (Platyhelminthes, Acoela). Acta Zoologica 83:15–24.

Tyler, S., and M.D. Hooge (2001). Musculature of Gnathostomula armata Riedl 1971 and its ecological significance. PSZN Marine Ecology 21:71-83.

Hooge, M.D., and S. Tyler (2001). Interstitial acoels (Platyhelminthes, Acoela) from Bermuda. Proc. Biol. Soc. Wash. 114: 414-426.

Tyler, S. (2001) The early worm—origins and relationships of the lower flatworms. In: Littlewood DTJ, Bray R (eds) Interrelationships of the Platyhelminthes, London: Taylor & Francis, pp 3-12

Tyler, S. and R. M. Rieger (1999) Functional morphology of musculature in the acoelomate worm Convoluta pulchra (Platyhelminthes). Zoomorphology 119: 127-141

Hooge M.D. and S. Tyler (1999) Musculature of the facultative parasite Urastoma cyprinae (Platyhelminthes). J. Morphology 241:207-216

Tyler, S. (1999) Platyhelminthes. In: Encyclopedia of Reproduction, E. Knobil & J.D. Neill, eds. Academic Press, San Diego, Vol. 3, pp 901-908

Tyler, S. (1999) Systematics of the flatworms—Libbie Hyman’s influence on current views of the Platyhelminthes. Am. Mus. Novitates No. 3277, pp 52-66.

Tyler, S., and M.S. Tyler (1997) Origin of the epidermis in parasitic platyhelminths. Internat. J. Parasitol. 27:715-738.

Rieger, R.M., S. Tyler, G.E. Rieger, and J.P.S. Smith (1991) Turbellaria. In Microscopic Anatomy of Invertebrates, Volume 3, Platyhelminthes and Nemertinea, F.W. Harrison and B.J. Bogitsh (eds), Wiley-Liss, New York. pp. 7-140.

Tyler, S., ed. (1991) Turbellarian Biology. Dr. W. Junk Publ., Dordrecht, The Netherlands. 398 pp.