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1

New observations on green hydra symbiosis

100%
Kovacevic G., Kalafatic M., Ljubesic N.
Folia Biologica
|
2007
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vol. 55
|
issue 1-2
77-79
EN
New observations on green hydra symbiosis are described. Herbicide norflurazon was chosen as a ?trigger? for analysis of these observations. Green hydra (Hydra viridissima Pallas, 1766) is a typical example of endosymbiosis. In its gastrodermal myoeptihelial cells it contains individuals of Chlorella vulgaris Beij. (KESSLER & HUSS 1992). Ultrastructural changes were observed by means of TEM. The newly described morphological features of green hydra symbiosis included a widening of the perialgal space, missing symbiosomes and joining of the existing perialgal spaces. Also, on the basis of the newly described mechanisms, the recovery of green hydra after a period of intoxication was explained. The final result of the disturbed symbiosis between hydra and algae was the reassembly of the endosymbiosis in surviving individuals.
2

Isolation and cultivation of endosymbiotic alga from green hydra and phylogenetic analysis of 18S rDNA sequences

100%
Kovacevic G., Franjevic D., Jelencic B., Kalafatic M.
Folia Biologica
|
2010
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vol. 58
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issue 1-2
135-143
EN
Symbiotic associations are of wide significance in evolution and biodiversity. The green hydra is a typical example of endosymbiosis. In its gastrodermal myoepithelial cells it harbors the individuals of a unicellular green algae. Endosymbiotic algae from green hydra have been successfully isolated and permanently maintained in a stable clean lab culture for the first time.We reconstructed the phylogeny of isolated endosymbiotic algae using the 18S rRNA gene to clarify its current status and to validate the traditional inclusion of these endosymbiotic algae within the Chlorella genus. Molecular analyses established that different genera and species of unicellular green algae could be present as symbionts in green hydra, depending on the natural habitat of a particular strain of green hydra.
3

Effects of norflurazon on green and brown hydra

100%
Kovacevic G., Kalafatic M., Ljubesic N.
Folia Biologica
|
2009
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vol. 57
|
issue 1-2
91-96
EN
For the first time effects of norflurazon on green (Hydra viridissima Pallas, 1766) and brown hydra (Hydra oligactis Pallas, 1766) in high- and low-light conditions were investigated in order to establish the extent of damage that this substance inflicts, with special emphasis on the .bleaching effect. and the effect on hydra-algae symbiosis. Green hydra is a typical example of an endosymbiotic organism. The gastrodermal myoepithelial cells of green hydra contain endosymbiotic algae. Norflurazon is a selective translocational herbicide that induces a .bleaching effect. on newly developed chloroplasts, resulting in a decrease of photosynthetic activity and viability of the organism. In the experiment, morphological (binocular), cytological and histological (Bouin fixative, dehydration, paraplast embedding, H?malaun-eosine staining, light microscope) and conventional transmission electron microscopy (cTEM) (glutaraldehyde, dehydration, raisin, uranyl-acetate, Pb-citrate) were used. Depending on the concentration and light conditions, norflurazon caused mortality, deformations, changes in behavior, locomotion and asexual reproduction, changes in the structure of all 3 layers in hydras, changes in the position and shape of endosymbiotic algae inside the hydra body as well as ultrastructural changes of treated hydras and endosymbiotic algae. Under low concentrations of norflurazon the effects on hydra were similar to the controls, while in the highest concentrations especially manifested were antichloroplastal and antimitochondrial effects. Norflurazon caused a great extent of damage and induced deleterious effects also upon other cellular components such as cellularmembranes, ER,Golgi apparatus, ribosomes. Newly developed buds in symbiotic green hydras were not bleached. After a recovery period, the green hydra individuals that had survived re-established regular endosymbiosis with algae and recovered completely, whereas brown hydras recovered only partially.
4

Karyological analysis of two allopatric populations of planarian Polycelis felina (Daly.) in Croatia

76%
Kalafatic M., Kopjar N., Zrna G., Zupan I., Kovacevic G., Franjevic D.
Folia Biologica
|
2004
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vol. 52
|
issue 1-2
131-133
EN
The results of preliminary karyological investigations of two geographically distant and morphologically slightly different Polycelis felina (Daly.) populations from central Croatia are reported. The results have shown that individuals of both populations are diploids, with the same chromosome number in their neoblasts (2n=18). Their karyotypes were composed of nine chromosome pairs, three of them are metacentric and the other six are submetacentric. Statistical evaluation of data indicated that both populations of Polycelis felina (Daly.), despite minor differences observed between them, belong to the same karyological biotype.
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