[Effect of variable phases of tide cycle on reproduction of Laomedea flexuosa (Hydroidea, Thecaphora].
Colonial hydroid Laomedea flexuosa inhabits the narrow belt of low littoral zone in the White Sea. What is a reason of so limited habitat? The authors studied the time of planulae release and its behavior during free swimming stages and settlement of larvae in nature and under laboratory conditions. Three methods were used to registrate the tidal dependent dynamic of planulae release: 1) plankton collecting bags around Fucus inflatus kelp with mature hydroids colonies; 2) active stirring kelps with hydroids in container with water, which is an old way to stimulate planulae release; 3) direct account of the mature planulae into gonangia. The dynamic of intensity of L. flexuosa planulae release was investigated according 3-4 phases of tidal cycle. All data were statistically tested. For L. flexuosa a moment of general larvae release was found in phase with the period of low water. This correlation could explain strict limitation in occurrence of L. flexuosa only in the lower part of intertidal zone. Laboratory experiments show that planulae release is stimulated by littoral drainage, and renewal of water movement during the beginning of tide. The decrease in time of planulae settlement is an affective way for marine sedentary species to stay in a narrow zone of optimal habitat.
Belorustseva
S A
SA
Dept. Invertebrate Zoology, Biological Faculty, M.V. Lomonosov Moscow University, Moscow 119899, Russia.
Marfenin
N N
NN
D000818:Animals; D003063:Cnidaria / Q000254:growth & development / Q000502:physiology*; D008386:Marine Biology; D016081:Moon; D012098:Reproduction; D012426:Russia