ИСТИНА

Nineteen hydromedusan species inhabit the White Sea and most of them can be collected in the Rugozerskaya inlet (Kandalaksha Bay). Most hydromedusae species in the Rugozerskaya inlet appear in the spring when the ice is melting. These species have maturated gonads in June. New colonies of Obelia longissima, Bougainvillia superciliaris, Rathkea octopunctata, Sarsia tubulosa, Halitholus cirratus, Catablema vesicarium started growth over the experimental glasses in June or July in 2012-2013. Medusa buds of Bougainvillia superciliaris and Sarsia tubulosa were collected at the end of March when the sea was covered by the ice and the temperature was negative. Others species such as Sarsia (Stauridiosarsia) producta and Obelia geniculata formed gonophores in the middle of the summer 2012 when the temperature of the sea had achieved 12-15ºC. Also the medusa buds of S.producta and S.tubulosa were observed at the end of August in 2012 when the temperature had descended till 10-12ºC. Because of rarity of the accurate observations of medusa budding process we know a little about the environment cues which regulate hydroids life cycles. In the rearing experiments we estimated the hypothesis of regulation of the life cycle of hydroids by temperature. The colonies of O.longissima and S.producta released medusae on time in spite of experimental temperature was 10-12ºC all the year. So we can suppose that medusa budding begin in according to endogenous rhythm if food supply and temperature are fit.