ИСТИНА

Pelagic coastal community in the sea is the complicated mosaic of alternate populations. Many meroplankton species send their larvae to the plankton. But also gelatinous carnivore (hydrozoan and scyphozoan medusae) appear in the periods of abundant zooplankton to feed and sexual reproduction. What are the environment cues which regulate this nature mosaic? In this research I checked if the temperature affects production of medusae in the White Sea. Nineteen hydromedusan and two scyphozoan species inhabit the White Sea and most of them can be collected near the Pertsov Biological Station (Rugozerskaya inlet, Kandalaksha Bay). Hydromedusae predate mainly on crustacean preys (Prudkovsky, 2013). In average they are usually insufficient to reduce the prey populations. But predation rate is highest in the rare areas or in the rare periods with high medusae abundance. Most hydromedusae species in the Rugozerskaya inlet appear in the spring when the ice is melting and only two species appear in the middle of the summer. Hydroid colonies Bougainvillia superciliaris and Sarsia tubulosa with medusa buds were collected in the sea at the end of March 2011-2013 when the sea was covered by the ice and the temperature was negative. Hydroids Coryne producta and Obelia geniculata produced medusae in July or August 2012-2013 when the temperature of the sea had achieved 10-15ºC. 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 I estimated the hypothesis of regulation of the life cycle of hydroids and scyphozoan polyps by temperature. In experiments five hydroid species (Bougainvillia superciliaris, Halitholus cirratus, Catablema vesicarium, Rathkea octopunctata, Obelia longissima) and scyphozoan polyp Cyanea capillata produced medusae in different seasons of year out of the usual periods. The repeated successful experiments in different seasons were carried out for Rathkea octopunctata and Catablema vesicarium. The schemes of experiments were the same for different species. The “temperature shift experiments” were carried out in 2013 after prolonged cultivation of species in the constant temperature conditions (0ºC, 5ºC or 10ºC). Several species (R.octopunctata, C.vesicarium, H.cirratus) produced medusae as a result of fall the temperature till 0-5ºC. On the contrary several species (O.longissima, C.capillata) produced medusae as a result of rise the temperature till 5-10ºC. Hydroid B.superciliaris produced medusa buds both after fall and after rise the temperature to the value 4-6ºC. I have not achieved the evident results for Sarsia tubulosa and Coryne producta. In experiment hydroid S.tubulosa produced medusae in the end of July or in September with invariable temperature 4-6ºC or 10-12ºC. These results are in contradiction with usual temperature at which hydroid produce medusae in the sea. Hydroid C.producta produced medusae for several months with invariable temperature 4-6ºC or 10-12ºC. It was occurred in the same period as in the sea. Some results pointed to complexity of life cycle regulation. The colonies O.longissima released medusae both in September after rise the temperature and in June with invariable temperature conditions. It is probably the shift in the food ration could induce the medusae generation in the last case. Also in the process of experiments I elucidated the life cycles of two Pandeidae species H.cirratus and C.vesicarium.