Effects of photosynyhetic activity in endosymbiotic zoochlorellae on gemmule germination of a freshwater sponge Radiospongilla cerebellata PDF
Preview Effects of photosynyhetic activity in endosymbiotic zoochlorellae on gemmule germination of a freshwater sponge Radiospongilla cerebellata
524 MEMOIRS OF THE QUEENSLAND MUSEUM EFFECTS OF PHOTOSYNTHETIC ACTIVITY sealed and isolated from the atmospheric gases, no IN ENDOSYMBIOTIC ZOOCHLORELLAE ON gemmules were germinated. When an air bubble was GEMMULE GERMINATION OF A introduced to the incubating chamber by one tenth or FRESHWATER SPONGE, RADIOSPONGILLA more the volume of the incubation medium 100% CEREBELLATA. Memoirs of the Queensland germination wasachieved. Museum 44; 524. 1999:- Many offreshwatersponges Ofthe majorelements ofair, only oxygen induced thrive inoligotrophie clearwaters in cooperationwith germination efficiently, and brought full germination photosynthetic endosymbionts, such as zoochlorellae atmuchlessquantitythantheair(aboutonehundredth in their mesenchymal cells. They also withstand ofthe incubating medium in volume). On the other unfavourable winter season in dormant forms as hand, nitrogen and carbon dioxide, showed noeffects gemmules. Annandale sponge Radiospongilla on the gemmule germination under the optimal cerebellata is a green freshwater demospongiae with condition. On the contrary, carbon dioxide showed zoochlorellaeintheirarchaeocytesandflourishesonly strong inhibition of gemmule germination in the in warmer season in southern district of Japan. oxygenated oraerated media. Theseresults show that Gemmules of the Annandale sponge also contain gemmules of the Annandale sponge are induced to zoochlorellae in thesocytes and germinate only under germinatebycytoplasmicoxygenconcentration under illumination even ifall other conditions are properly the favourable condition, but can be substantially provided. Although the light sufficient to induce the suppressedbycarbondioxide.Thus, itisregardedthat germination was very low in intensity and extremely lightappliedto thegemmuleswould initially promote short in illuminating period, photosynthesis seems to photosynthesis in the symbiotic chlorellae in the be essential for the germination, because a thesocytes, which would absorb cytoplasmic carbon photosynthetic inhibitor, atrazine, strongly inhibited dioxide and block the initiation and/orprogression of the germination underoptimal condition. gemmule germination, and evolve oxygen that SincegemmulesoftheAnnandalespongecontaina promotes gemmules to germinate. To confirm this rich storage of nutrients in the thesocytes, assumption, we have tried to induce germination in photosynthetic nutrients, produced during the darkness with fully oxygenated and carbon dioxide incubating period under very low intensity and short free media. However, no gemmules have germinated lengthofillumination, seem tohave littleeffecton the intotal darkness, inspiteofotheroptimal conditions. induction ofthegemmulegermination. We undertook The failure of germination in darkness can be to observe the effects of other factors on gemmule understood as follows: when optimal temperatureand germination, that is, gaseous components such as oxygen were provided to the gemmule cells, (which oxygen evolved and carbon dioxide consumed by had been dormant under the cold temperature), they photosynthesis. To accomplish gas experiments, we seemed to rouse and begin to respire, and generate devised a glass slide with a hollow chamber of3cm3 carbon dioxide. The carbon dioxide could not be sealed with a glass plate. In gas experiments, eliminated fromthecytoplasm readily, duetothe lack gemmuleswereplacedinthechamberwithM-medium ofphotosynthesis underdarkness, so its accumulation (previously boiled to eliminate dissolved gaseous in thethesocytes appearsto inhibitgermination ofthe O components). The chamber was tightly sealed with a gemmules. Porffera,freshwatersponges, gemmule, glass plate and the desired amount of gas was germination, symbionts,photosynthesis, 2, C02. introduced to the medium as a bubble underthe glass plate. Gemmules were illuminated at3000 lx through Y Satoh. Y Fujimoto, A. Yamamoto & Y. Kamishima the glass plate by ordinal fluorescent tubes for lOhrs (email: ykam(a}cc.okayama-u.ac.jp). Department of daily and kept at 24°C for 8 days. When gemmules Biology, Faculty' ofEducation, Okavama University, were incubated in degassed medium that was tightly Okayama, 700-8530, Japan; JJune 1998.
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