Effects of UVB radiation and norflurazon on green hydra (Hydra viridissima Pallas, 1776) and brown hydra (Hydra oligactis Pallas, 1776)

Postoje dokumentirana istraživanja o postojanju tumora na tijelu hidri, a ovo je prvo istraživanje gdje su jedinke hidre izlagane tretmanu UVB-zračenjem i/ili norflurazonu s namjerom da se izazovu tumori. Jedinke zelene hidre (Hydra viridissima Pallas, 1766) i jedinke smeđe hidre (Hydra oligactis Pallas, 1766) ili obje vrste zajedno izlagane su norflurazonu koncentracija 2x10-7 mol/L ili 2x10-6 mol/L. Dio hidri izložen je norflurazonu i zračen UVB-zračenjem valne dužine 254 nm 2 minute. Drugi dio pokusa je rađen tako da su hidrama dodane suspenzije slobodnoživuće alge Chlorella vulgaris (CV) i endosimbiotske alge Mychonastes homosphaera (CZ10) ili obje alge zajedno. Hidre s dodatkom algi su izlagane norflurazonu i zračene na isti način kao u prvom dijelu pokusa. Pratile su se morfološke promjene hidri: migracija, odgovor na mehanički podražaj, oblik tijela, oštećenje lovki, nespolno (pupanje) i spolno razmnožavanje te smrtnost. U eksperimentalnim posudicama s dodatkom algi pratile su se još boja otopine i prisustvo nakupina algi. Migracija hidri, promjena oblika tijela pretežno iz relaksiranog u kontrahirani oblik i spolno razmnožavanje bili su prvi znakovi izbjegavanja štetnog učinka UVB-zračenja ili norflurazona. Histološke promjene pratile su se svjetlosnim mikroskopom i brojale su se stanice ektoderma, gastroderma, intersticijske stanice, zimogene stanice i žarne stanice, a mjerena je i debljina mezogleje. Ugibale su samo zračene jedinke zelene hidre. Pri višoj koncentraciji norflurazona i u svim zračenim hidrama uočena su velika oštećenja u strukturi tkiva hidri. Zračenje je prouzročilo izrasline na lovkama i na tijelu hidre ili specifične rašljaste lovke The occurence of tumors on the body of hydra has already been reported in researches but this is the first study in which the individuals of symbiotic green hydra and nonsymbiotic brown hydra were exposed to UVB-radiation and /or norflurazon in order to induce tumors. The individuals of green hydra (Hydra viridissima Pallas, 1766) and brown hydra (Hydra oligactis Pallas, 1766), either separately or both species together, were treated with norflurazon in concentrations of 2x10-7 mol/L or 2x10-6 mol/L. A group of hydra was treated with norflurazon and exposed to UVB-radiation with a wavelenght of 254 nm for 2 minutes. The second part of the experiment was performed by adding suspensions of free-living algae Chlorella vulgaris (CV) or endosimbiotic Mychonastes homosphaera (CZ10) and both algae together. The group of hydra with algae suspension was treated with norflurazon and exposed to UVB-radiation in the same way as in the first part of the experiment. The following morphological changes of hydra were observed: migration, response to mechanical stimuli, body shape, damage to tentacles, asexual (budding) and sexual reproduction, and mortality. The experimental dishes with algae suspension were monitored for the change of solution color and the presence of algae blobs. Migration, change of body shape from relaxed to predominantly contracted, and sexual reproduction were identified as the first evasion signs of the deleterious effects of UVB-radiation and norflurazon. Histological changes were detected by light microscope, while ectoderm, gastroderm, interstitial, zymogen and cnidocyte cells were counted. The thickness of mesoglea was measured. Mortality was present in the individuals of green hydra that were exposed to UVB-radiation. Severe damage to the structure of hydra tissue was noted in hydra treated with high concentrations of norflurazon and in all hydra exposed to UVB-radiation. Radiation caused tissue growths on both tentacles and body of hydra as well as specific fork-shaped tentacles in hydra.