Doctoral Dissertations

Date of Award

8-1980

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Botany

Major Professor

Patricia L. Waine

Abstract

The ultrastructure of the phacotacean flagellate, Pteromonas protracta (Volvocales), was investigated, with special reference to lorica structure, composition and development. The bilayered lorica is composed of 2 valves that are closely appressed to the protoplast. The valves are fused, forming a wing which circumscribes the cell. The wing extends from the lorica of 1.5-2.0 um. A third, wedge-shaped lorica segment with 2 flagellar pores is located at the anterior end of the cell and is fused to both valves. The surface of the outer lorica (OL) is covered with a raised hexagonal pattern; a secondary reticulum between the hexagonal ridges, is characterized by numerous puncta. Different culture media affect lorica structure but not basic elemental composition. In mature loricas from modified soil water (MSW) cultures, the OL is dense and amorphous with a scalloped margin which corresponds to the hexagonal surface pattern. The inner lorica (IL) is granulo-fibrillar and closely appressed to the OL. In cells grown in modified Bald's Basal Medium (MBBM), the IL is finely granular, and the OL is broad and diffuse with the hexagonal pattern obscured by a copious mucilaginous layer. The major elements detected in all loricas analyzed by Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDX) and Scanning Transmission Electron Microscopy-Energy Dispersive Spectroscopy. (STEMEDX) are P and Ca, and Si is detected in over 85% of the loricas, regardless of culture medium or age. Sulfur is present in over 50% of the loricas from either medium, while Fe is present in 87% of loricas from MSW cultures but never detected in loricas from MBBM cultures. Other elements such as Cr, Cl, Al, Mg, K, Mn, Ni and Hg are found in less than 50% of all loricas and are often removed from them by treatment with glusulase, a result suggesting that they are loosely associated with the mucilage component of the loricas. Results of tests with a variety of cytochemical stains indicate that the mucilage is an acidic and negatively charged mucopolysaccaride containing a protein moiety. That Ca is localized in the primary hexagonal pattern and forms the basic structural component of the OL is suggested by analysis of loricas subjected to acetolysis and EDTA and EGTA treatment. Observations of loricas treated with dilute HCl indicate that the Ca might be in the form of calcite.

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