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The Bryophyte Spermatozoid: A Source of New Phylogenetic Information

Zane B. Carothers and Jeffrey G. Duckett
Bulletin of the Torrey Botanical Club
Vol. 107, No. 3 (Jul. - Sep., 1980), pp. 281-297
Published by: Torrey Botanical Society
DOI: 10.2307/2484152
Stable URL: http://www.jstor.org/stable/2484152
Page Count: 17
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The Bryophyte Spermatozoid: A Source of New Phylogenetic Information
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Abstract

This paper reviews comparative ultrastructural studies that reveal possible trends of specialization in developing or mature spermatozoids of bryophytes. Included in an introductory resume of spermatogenesis are new data on the microanatomy of the multilayered structure (MLS) in Dumortiera, while other micrographs provide new information on spline width and MLS structure in Fossombronia, Symphyogyna and Monoclea. Most emphasis is given to comparative blepharoplast morphology in five taxa: the liverworts Haplomitrium and Marchantia, the hornwort Phaeoceros and the mosses Sphagnum and Polytrichum. Reaching its greatest degree of structural complexity in the young spermatid (immature spermatozoid), the blepharoplast-a component of the cell's locomotory apparatus-offers a dozen or more characters for comparison. Those characters pertaining to the MLS include the shape and maximum width of the spline or microtubular cytoskeleton, absence or presence and position of a slot-like spline aperture, and the shape, length and width of the typically three-layered lamellar strip which subtends the spline. Other blepharoplast characters include lengths of anterior and posterior basal bodies, the basal body positions relative to each other, their angular orientation relative to the spline axis, and the absence or presence and length of the stellate pattern in the flagellar transition zone. Reconstructions show that each of the blepharoplasts is distinctly different from the others. Blepharoplasts of hepatics and mosses have many more characters in common than do those of either group with the hornworts, and for the hepatics it appears that from the putatively primitive Haplomitrium-type blepharoplast there has been a shift toward reduction of structural complexity in the more advanced taxa. Other evidence suggests that comparative morphological studies of fully formed, prerelease spermatozoids may offer additional clues to bryophyte evolution.

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