Taxonomic diversity of macrandrous species of Oedogonium Link ex Hirn (Chlorophyceae: Oedogoniales) with emphasis on ecology from Hooghly, West Bengal

The present paper includes detail taxonomic features of nine taxa of Oedogonium Link ex Hirn (Chlorophyceae: Oedogoniales) collected from Hooghly district, West Bengal, India. These taxa are Oedogonium bharuchae N.D. Kamat, Oedogonium cardiacum f. pulchellum Hirn, Oedogonium crispum var. pyriforme (Wittr. ex Hirn) A.K.M.N. Islam et P. Sarma, Oedogonium gunnii Wittr. ex Hirn, Oedogonium khannae f. minus Gonzalves et S.C. Jain, Oedogonium nanum Wittr. ex Hirn, Oedogonium pratense Trans., Oedogonium rivulare A. Br. ex Hirn and Oedogonium vaucheri A. Br. ex Hirn. All those taxa were found to grow epiphytically on the leaves and stems of submerged hydrophytes as filaments in quiet lentic freshwater bodies after the end of rainy season. Twelve limnological parameters like temperature, pH, DO, BOD, COD, NO3-N, PO43-, Cl-, free CO2, TDS, total hardness and turbidity of algal habitats were analyzed and found conducive for their occurrence and growth up to maturity (formation of fertile structures). The result of limnological study also indicated that all these species preferred to grow alkaline pH, less turbid and hard water. Studied limnological parameters recorded as water temperature: 17.5 oC-20 oC, pH range from 7.1-7.6, high dissolved oxygen (DO) concentration 6.4-7.2 mg.L^-1, BOD values < 20.0 mg.L^-1, moderate COD values and lower nutrient levels with other parameters like Cl-, free CO2, TDS, turbidity as 6.8-9.0 NTU and also hard nature of water ranged from 120-204 mg.L^-1.

DNA and heterochromatin cycles in male gamete development of Oedogonium

In antheridial nuclei of <em>Oedogonium cardiacum</em> (Hass.) Wittr. during male gamete formation, the DNA presynthetic period is shortened, the synthetic and postsynthetic periods are lengthened (G₁ - 15%, S - 58%, G₂ - 29%) as compared with those in vegetative cells (G₁ - 31%, S - 44%, G₂ - 25%). Differences in the ratio of the relative amounts of eu- and heterochromatin in the antheridial mother cell (AMC) nucleus and antheridial cell nucleus were determined. Hydrolysis curves revealed two peaks of higher optical density (3.5 and 8.5 h hydrolysis with 5N HCl at 23°C), corresponding to eu- and heterochromatin. Heterochromatin in antheridial cell nuclei was characterized by a greater optical density than that of heterochromatin in AMC nuclei. The presence of two local optimal density maxima is considered as facultative and constitutive increasing of chromatin condensation in the process of male cell development.

THE EFFECTS OF ISOPROPYL N-PHENYL CARBAMATE ON THE GREEN ALGA OEDOGONIUM CARDIACUM

Cell division in vegetative filaments of the green alga Oedogonium cardiacum is presented as an experimental system. We report on how we have used this system to study the effects of isopropyl N-phenylcarbamate (IPC) on the mitotic apparatus and on the phycoplast, a planar array of cytokinetic microtubules. Polymerization of microtubules was prevented when filaments, synchronized by a light/dark regime and chilled (2°C) while in metaphase or just before phycoplast formation, were exposed to 5.5 x 10-4 M IPC and then returned to room temperature. Spindles reformed or phycoplasts formed when these filaments were transferred to growth medium free of IPC. However, the orientation of both microtubular systems was disturbed: the mitotic apparatus often contained three poles, frequently forming three daughter nuclei upon karyokinesis; the phycoplast was often stellate rather than planar, and it sometimes was displaced to the side of both daughter nuclei, resulting in a binucleate and an anucleate cell upon cytokinesis. Our results suggest that IPC (a) prevents the assembly of microtubules, (b) increases the number of functional polar bodies, and (c) affects the orientation of microtubules in O. cardiacum. High voltage (1,000 kV) electron microscopy of 0.5-µm thick sections allowed us to visualize the polar structures, which were not discernible in thin sections.