| Summary: | 博士 === 國立海洋大學 === 水產養殖學系 === 89 === Studies on the gametogenesis and ultrastructure of algal gamete can provide not only references for the classification of brown algae, but also an ultrastructure-based assessment of algal evolutionary relationships within a class and between classes. In addition, the results also establish a basic referential ultrastructure model to the morphology study of the sequential development of gametes. This study, thus, launch on an ultrastructure observation of gametogenesis and its morphology of Endarachne binghamiae by cultivating ripe E. binghamiae thalli with dark brown patches in 12-18℃ dark incubator for 16 hours to collect newly released gametes and thalli for observations under SEM and TEM. Under the observation of TEM, only outer layer cells at the upper end of the cultivated thallus were found to release active gametes through mitosis and transformation. Meanwhile, four distinctive features of these newly released gametes are found under SEM and TEM; they are: (1) existing of two types of gametes which are characterized by different vesicles secreted from Golgi apparatus of different gametes, (2) the bypassing microtubular root consisting of about 13 microtubules, (3) a translucent space between eyespot and lamella, and (4) isogametes having some coiled fibrils in the anterior and posterior basal bodies being proximal to its transition region. The 4th finding especially can support the arguement that Sarcinochrysidales is ancestral to Phaeophyta. It may also be inferred that the phylogenetic relation of E. binghamiae to Sarcinochrysidales is closer than other brown algae to Sarcinochrysidales.
Ultrastructural observations of gametes during their TEM is employed in the follow up observation on the development of the released gametes from singly and mixedly cultivated thalli. Gametes released from these two groups of thalli is found to undergo gamete fusion. Obviously, the thalli have developed into gametophyte and E. binghamiae is definitely a monoecious or dioecious alga in which gametic fusion can be carried out between isogametes.
Previous light microscopic observations on the released isogametes, growing in a conditions of 50µE·m-2 s-1、20℃、12/12h(L/D) have found the various development patterns that can not be classified into specific reproduction mode. Therefore, three different kinds of solutions that can paralyze flagellar motility at their lowest dosages, i. e. 0.012%(v/v) formaldehyde (dissolved in filtered seawater), 0.105%(w/v) EDTA and 0.198%(w/v) EGTA (dissolved in filtered distillwater), are used in the last research of this study to initiate only parthenogenesis of isogametes for clear differentiation of parthenogenesis from sexual and asexual reproduction modes.
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