جستجوی مقالات مرتبط با کلیدواژه « دافنی ماگنا » در نشریات گروه « علوم پایه »

This study was carried out to investigate the effect of Microcystin-RR (MC-RR) extracted from Microcystis aeroginosa microalgae on Daphnia magna and determine the lethal concentration of this toxin (LC50-96h). Twenty-one Daphnia magna were exposed to concentrations of 0.5, 2, 10, 20 and 50 μg.ml-1 of MC-RR Microcystin in each replicate, and the daphnia survival for 24 to 96 hours was calculated. One treatment was considered as control (no toxin), each treatment had 3 replications. According to the results of this study, microcystin (MC-RR) had a lethal effect on Daphnia magna, so that even at a low concentration (concentration of 0.5), about 38% of mortality was observed, and none of the Daphnia magna had the ability to survive at 2 μg.ml-1 of pure MC-RR Microcystin for 96 hours. This ability decreased by increasing the concentration of poison, so that at the concentration of 10 μg.ml-1 of Microcystin, on the second day and at concentrations of 20 and 50 μg.ml-1 of poison, all daphnia were dead on the first day. The results of this study showed that in the concentration of 1.75 μg.ml-1 MC-RR Microcystin, during 96 hours, 99 percent of daphnia were died.

Beluga (Huso huso) larvae with average body weight of 30.43 ± 1.25 mg and density of 2 fish per liter having three replicates (100 fish per tank) were fed on the 30 percentage of body weight in a day during 15 days using Daphnia magna, Artemia urmiana nauplii and mix of Artemia and Daphnia magna, Artemia urmiana nauplii and the mix of them (Daphnia 50% w/w and Artemia 50% w/w) in a completely randomized design. The fish was weighed individually at the start and the end of the experiment. The carcass proximate compositions of samples of fish were determined. The maximum of carcass crude protein (76.70%) and lipid (8.83%) was obtained in treatments of Artemia and showed significantly difference with treatment of Daphnia and mix of Artemia and Daphnia, respectively (P<0.05). Thesignificant difference in protein, lipid and energy productive value were observed among the treatments (P<0.05). The highest energy retained as protein (13.76 J/day) and lipid (45.14 J/day) were observed in treatment of Daphnia. The best final body weight (193.98) and feed conversion ratio of 2.80 were observed in treatment of Daphnia. The maximum specific growth rate in protein (SGRP), lipid (SGRl) and energy (SGRe) were obtained in fish that fed on Daphnia. The results of this experiment showed that the potential of Huso huso larvae in using of Daphnia magna, Artemia urmiana nauplii and mixture of them was different and Daphnia had a suitable effect on promotion of feeding parameters in larval stage.

Fenitrotione is one of the popular organophosphorus insecticides that is using in gardens and farms، which in this research the effects on mortality rate، filtration rate and intake in Daphnia magna، as an important zooplankton in aquatic ecosystems، was investigated. This organism has high feeding value for all fresh water fingerlings especially for marketing fish. Also the culturing of D. magna is one of the necessary purposes in fertilizing of rearing fish ponds. In this study، D. magna was used as indicator organism in ecotoxicological test. This study was done in static method for 24h، a design of 5 treatments (0. 005، 0. 01، 0. 02، 0. 04 and 0. 1) was arranged with three replicates. All water physico-chemical parameters such as temperature، pH، dissolved oxygen، hardness and electrical conduction were controlled. Chrorella volglaris (10 mg/l) was used to detect filtration rate and intake by D. magna and observed that with increasing Fenitrotione concentration، filtration rate and intake were decreased. According to the present research، Ec10 (Effective Concentration 10)، Ec50 (Effective Concentration 50) and Ec90 (Effective Concentration 90) were 0. 004 mg/l، 0. 011 mg/l and 0. 028 mg/l، respectively. Also maximum allowable concentration (MAC)، low observe effect concentration (LOEC) and none observe effect concentration (NOEC) were 0. 0011 mg/l، 0. 005 mg/l and 0. 00011 mg/l، respectively. It means that this insecticide is high toxic for D. magna. Hence we can conclude that Fenitrotione is very toxic for D. magna and the entered amount was more than EC10 in fresh water ecosystems، this phenomenon.

The Daphnia magna is a promising candidate for feeding freshwater fish larvae in cultural media. In this research، the effect of two Cyanophycae strain (Anabaena flosaquae and Oscillatoria africanum) on ingestion، filtration rate and feeding behavioral of Daphnia magna were investigated. Exposure was down at the same condition in three replications. Rate of filtration، ingestion and feeding of Daphnia magna from two investigated Cyanophycae strain were measured according to Gauld equation (1951). The results shown that with increasing of food concentration (Cyanophycae strains)، filtration، ingestion and feeding rate of Daphnia magna significantly decreased (P<0. 05). Maximum of these indices (798±60. 2، 70861± 992 and 0. 4±0. 02 respectively) in 3 mg/lit and minimum of mentioned parameters (100±17/7، 10683±492 and 0. 2±0. 01 respectively) were observed in 12 mg/lit. It means that Daphnia not able to filtered filamentous Cyanophycae makes some difficulty in filtration system of Daphnia، especially in high concentrations. The maximum of specific growth rate (SGR) (0. 5±0. 02) was observed in feeding with Anabaena flosaquae (in 4. 25 mg/l) (P<0. 05)، and survival rate of Daphnia magna not difference among mentioned algae (P>0. 05). According to the results can conclude that it is difficult to use Daphnia magna biological control of algal bloom in fresh water.

The aim of this study was to investigate the mean time of hatching of D. magna resting eggs under some abiotic factors. To do so, resting eggs were collected from different parts of live food ponds in Sad Voshmgir Cultivation and Breeding Centre of Gorgan, and after isolation, the eggs were kept in dry and wet conditions at 4°C for 2 months in darkness. Following the pre-incubation period, the two aforesaid groups were subdivided into 2 smaller parts and each was floated in 1% NaOCL and distilled water for 5 min. AdaM medium was used to determine the effect of photoperiod levels (continuous illumination, 12h light day-1) and temperature levels (20ºC, 25ºC and 30ºC) on the hatching time of resting eggs and the incubation period last for 15 days. On the obtained results, the incubation of wet eggs of this species and their subsequent exposure to continuous illumination at 20ºC and 25ºC had a significant shortening effect on the mean time to hatch (P<0.05(