Electron microscopic investigations of aspects of red algal reproductive differentiation and developmental morphology

• Main Author: Broadwater, Sharon Thompson
• Format: Others
• Language: English
• Published: W&M ScholarWorks 1984
• Subjects: Marine Biology
• Online Access: https://scholarworks.wm.edu/etd/1539616581; https://scholarworks.wm.edu/cgi/viewcontent.cgi?article=2149&context=etd

Ultrastructural studies of meiosis, as well as aspects of vegetative and reproductive development, in three species of red algae were conducted. An account of meiosis in Dasya baillouviana is presented and represents the first comprehensive account in red algae. In early prophase I, the nuclei of tetrasporangia have, first, axial cores and, later, synaptonemal complexes as well as an electron-lucent space of undetermined significance. In later stages, chromatin relaxes, presumed RNA synthesis occurs and cell size and organelle number greatly increase. Electron-dense bodies were found in the cytoplasm and compared to nuage, a substance found to be RNA in other organisms. Meiotic events from prometaphase I to telophase II were similar to accounts published for mitosis in higher red algae. A distinct interkinesis was present, a finding which disproved an earlier interpretation of uninuclear meiosis in red algae. Also of interest were large accumulations of smooth ER at the division poles and the presence in post-division of intranuclear structures thought to be polycomplexes. In addition, post-division nuclei were found to move simultaneously to the center of the cell, associate, possibly fuse and then move back prior to cytokinesis. This report recognizes, for the first time, the fibrous vacuole associated organelle (FVAO), a new organelle in red algae believed to give rise to fibrous vacuoles and possibly to process the contents of the vacuoles. of taxonomic significance was the correct identification of elements of the FVAO previously misinterpreted as intracellular flagella. A three-dimensional reconstruction of the chondriome of red alga (Rhodella reticulata) was made for the first time. The chondriome consisted of one large, ramifying mitochondrion with two very small fragments. Two other serially-sectioned cells were traced but not reconstructed. All the chondriomes were much like those found in other unicellular organisms from many phyla. This research indicated that although red algae have some very unique characteristics, cell morphology and development as well as characteristics of nuclear division do not indicate exceptionally primitive organisms.