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1
Examining Blastoid Morphology via Electron
Microscopy
Hannah Hunter, Department of Geosciences,
University of West Georgia Faculty advisors
Julie K. Bartley, Department of Geosciences,
University of West Georgia Colin Sumrall,
Department of Earth and Planetary Sciences,
University of Tennessee
Introduction The purpose of this project was to
examine more closely the internal morphology of a
disarticulated specimen of Pentremites
symmetricus using a Quanta SEM (scanning electron
microscope), in hopes of better understanding the
structure and function of the organism.
Analysis and Results Previous studies of the
blastoid conclude that hydrospires were the
primary respiratory organ of the organism. It
was also noted that these hydrospire structures
have a network of folds comprised of mesh-like
stereom (ref). Under the electron microscope,
the porous quality of the stereom is evident.
This porous covering might have allowed for the
passive transport of liquid across the skeleton
of the blastoid during life.
Deltoid pieces also show different types of
stereom. Could this mean each type functioned
in a diverse manner?
On closer inspection, a blastoids calcified side
plates show different types of stereom.
Methods Disarticulated skeletal elements were
identified and sorted by Dr. Colin Sumrall. Each
element was viewed first under a low-power
reflected light microscope, to establish the
basic morphology of the piece, including folds,
ridges, abnormal formation, etc. Following this
initial survey, the SEM was used to make a more
detailed assessment of each piece, identifying
stereom, porous structures within the blastoid,
and other important morphological components.
Images were captured of the each skeletal
element.
Conclusion Based upon the findings
Various external views of the blastoid lancet
formation, deltoid body region, and apex
hydrospire pores as seen through the Quanta SEM.
Hydrospires may have functioned in blastoid
respiration here we can see the hydrospire folds
have a mesh like network of pores that may have
allowed for water diffusion.
References Beaver, H.H., Caster, K.E., Durham,
J.W., Fay, R.O., Fell, H.B., Kesling, R.V.,
Macurda Jr., D.B., Moore, R.C., Ubaghs, Georges,
and Wanner, Johannes, 1967, Treatise on
Invertebrate Paleontology The Geological Society
of America, Inc. Echinodermata 1, Volume 2, p.
298-445. Boardman, Richard S., Cheetham, Alan H.,
Rowell, Albert J., Fossil Invertebrates Phylum
Echinodermata Class Blastoidea, 1987, p.
581-584. Smith, A.B., 1980,