SCHUETTE, S.W.*, A.R. MADEN, D.P. WHITTIER, AND K.S. RENZAGLIA. Department of Plant Biology, Southern Illinois University, , Carbondale,IL 62901 , Department of Biology, Vanderbilt University, Nashville, TN 37235. - Ultrastructure of the spermatozoid of Diphasiastrum digitatum.
The ultrastructure of motile cells provides valuable information in
assessing phylogenetic relationships among lycophytes. In
continuation of our studies of spermatogenesis, we examined the
ultrastructure of spermatozoids of Diphasiastrum
digitatum. The mature sperm cell is obovoid, biflagellated,
and contains relatively little cytoplasm. The elongate nucleus
occupies most of the cell and contains large spherical inclusions. A
multilayered structure wraps laterally around the anterior of the
nucleus and is subtended by a single mitochondrion. The two adjacent
basal bodies are staggered and slightly skewed from parallel. The
flagella emerge from the same side of the multilayered structure and
coil at least twice around the cell in parallel. A wide spline of
150-200 microtubules encases most of the diameter of the nucleus. At
the posterior of the cell, a short but wide spline shank supports a
large starch-laden plastid. Numerous small mitochondria are abundant
in this region. To illustrate architectural relationships among
cellular entities, we will present a three-dimensional reconstruction
of the mature spermatozoid of Diphasiastrum. This cell has
specific features in common with sperm cells of Lycopodium,
Huperzia, Phylloglossum, and Lycopodiella.
Phylogenetic relationships among these taxa will be evaluated by
analyses of data derived from male gametogenesis.
Key words: Diphasiastrum digitatum, spermatogenesis, ultrastructure