بررسي تغييرات سالانه جمعيت ، چرخه توليد مثلي و پراكنش كرم پرتار Hypania invalida در ساحل شهرستان نور-جنوب درياي خزر

Annual study of population dynamics, reproductive cycle and dispersal of the Hypania invalida, in the Noor Coast-The south of the Caspian Sea

In this study, Annual population dynamics and reproduction cycle and dispersal of Hypania invalida, in 5, 15 and 30 meter depths of the Noor Coast was studied seasonally during a year (2004-2005).Results revealed except spring the density and biomass of Hypania invalida,, during other seasons, decreased with increasing depth, total organic mater and decreasing sand percentage of the substrate. Maximum density and biomass of this worm were observed 1196.30±105.29 ind/m2 and 1076.67±94.76 mg/m2 in 30 meter depth at spring. In seasonal study, maximum and minimum density and biomass were obtained at Spring and Summer respectively. Eggs bearing females were observed in five month (March-July), but reproduction peak was obtained in March and April. Maximal egg diameter was obtained 154 micrometers and the egg number was 40 - 76.