Habitat characteristics for different freshwater snail species as determined biologically through macroinvertebrate information.

Macro-invertebrates including freshwater snails collected from 643 sites over 8 successive seasons among the River Nile, branches, main canals and certain drains in eight Egyptian Governorates. Thirteen snail species and one bivalve species were identified. The most distributed were Lanistus carinatus and Physa acuta while the most abundant were Cleopatra bulimoides and Physa acuta during the whole study. The sites that harbored each snail species in all the examined water-courses were grouped seasonally and their biological assessment was determined by their minimum and maximum total point similarity percentage to that of the corresponded reference site and mean of the total points. Habitats for most snail species attained minimum total point's similarity percentage less than 21% (very poor habitat) during autumn and winter then spring while during summer very poor habitat was harbored by only few snail species. P. acuta was the only survived snails in habitat which attained 0 as a minimum total point's similarity percentage during two seasons and L. carinatus and Succinea cleopatra during one season. With respect to medically important snails very poor sites constituted 23% of Biomphalaria alexandrina sites, 14% of Lymnaea natalensis and 9.4% of Bulinus truncatus sites. The studied macroinvertebrate matrices, total number of organisms, taxa richness, the Ephemeroptera, Plecoptera, and Trichoptera (EPT) index, ratio of EPT index to chironomidae, ratio of scraper to filtering collector, contribution of dominant macroinvertebrate major group, comparison revealed descending tolerances from B. alexanrina followed by L. natalensis then B. truncates, but Hilsenhoff Biotic Index (HBI) showed the same tolerance to organic pollution.

Chemical and biological assessment for Egyptian surface freshwater environment with reference to human activities.

The Egyptian freshwater was assessed in the River Nile, branches, main canals and certain drainages in eight Governorates, over eight successive seasons starting from spring 2008. Chemical assessment was made through ten parameters and the biological one was made through macro-invertebrates information. Results showed that means of Cd, Pb, Cu, Hg, Mn, Fe, Ni, Na, K & Ca varied in watercourses seasonally within somewhat narrow ranges, which may exceed the level of concern but with some elevations in branches, Rayahs and canals during certain seasons. Sites showed chemical levels over the permissible one or those gain total points < or = 6.3 according to the biological assessment indicate that very poor habitat or those of Hilsenhoff Biotic Index (HBI) equal to 7-10 indicate that organic pollution were observed in all the studied watercourses reflecting hazard non point source pollution. Damietta branch in the region of Damietta city characterized with elevations in the concentration of most chemicals examined. The percentages of sites that showed chemical level over the permissible one were 70.56% for K, 54.08% for Cu, 50.08% for Na, 22.08% for Cd, 11.36% for Fe, 5.6% for Pb, 1.92% for Ni, 1.12% for Mn, 0.16% for Ca and at last 0.0736% for Hg. The biological assessment was more able to define more polluted sites than did the chemical one. Human activity data revealed that each of the drains, Giza and Qalyubia canals showed the highest item conduction (animal or plant waste, macroscopic pollution and presence of bridges or barriers) and this was co parallel with their highest pollution recordation.

Efficacy of temperature, and two commonly used molluscicides and fertilizers on Fasciola gigantica eggs.

This study evaluated the effect of temperature, molluscicides (Copper sulphate and Niclosamide), fertilizers (Superphosphate and Ammonium sulphate) on the hatchability of Fasciola gigantica eggs. The results showed that hatchability decreased to 4% when eggs were incubated in bile secretion at 37 degrees C for 5 days and to 1.4% for 10 days, but few eggs incubated in water at 37 degrees C hatched. Bile secretion at 37 degrees C was a poor medium for in-vitro egg preservation. But, hatching occurred only when eggs were transferred to water at 26 degrees C. Temperature fluctuation from 26-4 degrees C or from 32-4 degrees C had an inhibitory effect on embryos development (35.2% & 32.3%, respectively) as compared to controls (60% & 63.9%, respectively). The incubation period (19 & 17 days) was higher than controls (14 & 12 days, respectively). The LC50 & LC90 of Copper sulphate and Niclosamide against Biomphalaria alexandrina and Lymnaea natalenesis had no toxic effect on Fasciola eggs. The higher concentrations of Copper sulphate (30 ppm) and Niclosamide (1 ppm) slightly lower eggs hatchability rate than controls. The rate decreased by increasing the exposure time from 3 to 6 hours with both molluscicides. Ammonium sulphate had a lethal effect on eggs, but Superphosphate had some inhibitory effect on egg development, which increased by increasing Superphosphate concentration or with the prolongation of the exposure time.

Laboratory studies on the effect of magnetic technologies on some biological parameters of Biomphalaria alexandrina in Egypt.

The effect of magnetic water on some biological parameters of B. alexandrina was investigated. The growth rate, egg laying capacity, hatchability of deposited eggs, development of the newly hatched snails and the mortality rate of the treated snails (maintained in magnetic water for 12 weeks) were determined and compared with control ones maintained in normal water. The mean length of the diameter of treated snails after 12 weeks exposure to magnetic water (6.8 +/- 0.93) was slightly greater than the control group (6.4 +/- 0.8). Also, a highly significant increase in number of eggs and egg-masses of treated snails (8.06 +/- 6.55 & 1.14 +/- 0.8, respectively) as compared with controls (2.5 +/- 1.2 & 0.33 +/- 0.14, respectively). Hatchability rate of treated eggs in magnetic water for a period of 5 days was higher (63.4%) than the control group which recorded 28.2%. However, a highly significant reduction in the survival rate of newly hatched snails (22.5%) maintained in magnetic water for another 7 days after hatching as compared with the control (61.5%). Also a highly significant reduction in the survival rate of adults in magnetic water for 12 weeks which recorded 40% in contrast with the control ones, recorded 88%, (P < 0.001). There was slight decrease in the calcium content of the shells of treated snails (25.44% of wt.) as compared to controls (29.58% of wt.). The haermaphrodite gland acini of snails in magnetic water for 12 weeks were most frequently in final stages of oogensis and spermatogenesis. There were a significant increase in the mean number of 2ry oocytes and mature ova in acini of treated snails comparing with the control group (P < 0.05).

Food composition and feeding habits of some fresh water fishes in various water systems at Abbassa, Egypt, with special reference to snails transmitting diseases.

Study of feeding habits of freshwater fishes collected from ponds at World Fish Center (ICLARM) showed that the African catfish, Clarias gariepinus and Forskal catfish, Bagras bayad had the highest proportion of full stomachs (31-58% & 44-45% respectively). In cichlid fishes, the rate of full stomachs was much lower, being 0.0-12.5% and showed higher incidence of empty stomachs that varied from 37.5% for Oreochromis niloticus to 78.3% for Sarotherodon galilaeus. Food items were analyzed by the percentage of point assessment (P%), abundance (N%) and frequency of occurrence (F%). Results of the three methods of analyses (Index of relative importance, I.R.I) emphasized the importance of plants (1214.7) as a major food resource in the stomach of Nile tilapia, O. niloticus followed by shell fragments (628.5), whereas, snail soft bodies were the main food category in the diet of hybrid tilapia O. niloticus x O. aureus (2539.3). Shell fragments (652) and snail soft bodies (296.9) were the 1st in relative importance as foods of O. aurea. In case of S. galillae, shell fragments (338) came 2nd in I.R.I. after plants (559). Present investigation shows that shell fragments were represented by 11.1% and 15.1% in the diet of African catfish, C. gariepinus by (N%) and (P%) methods, however, they came as the second food item in its diet by I.R.I (1237.3). According to F% method, both shell fragments and Crustacea were present in the diet of C. gariepinus considerable proportions each of 47.4%. Shell fragments were represented by low proportions in the diet of B. bayad 3.9, 2.1 and 22.2 by N%, P% and F% respectively.

Feeding ecology and food composition of the black carp Mylopharyngodon piceus and the grass carp Ctenopharyngodon idella inhabiting the fish pond of Al-Abbassa fish hatchery with emphasis given to vector snails.

Stomach contents of M. piceus and C. idella collected from earthen fish ponds at Al-Abbassa fish hatchery during different seasons were examined. Food items were analyzed by three methods; the numerical (N%) percentage of point assessment (P%) and frequency of occurrence (F%). A comparison of the different methods emphasized the importance of snails as the major food resources in the diet of M. piceus during all seasons. During winter, stomachs of the most fish samples collected from fish ponds were empty or had traces of food. The index of relative importance (I.R.I) indicated that snails were the major food category in the diet of M. piceus during summer, autumn and spring represented by 7331, 9696 and 11670 respectively. Plants were the main food item in the diet of C. idella during summer (4604), meanwhile they came 3rd in relative importance in the diet during autumn and spring. Artificial fish food came as the 2nd food item in the diet of M. piceus during summer (1398.9) and autumn (5896.3) but it completely absent in spring. It is considered the main food item in diet of C. idella during autumn (10384.3) and spring (6293.5) and being 3rd in summer (1395.5). The results showed that snails reached highest level in the diet of M. piceus during spring (about 80% of all diet, decreased during summer (about 70%) and reached lowest proportion in autumn (50%). Plants exhibited marked seasonal variation in abundance with maximum level during summer (about 41% of all diet decreased during spring (27%) and autumn (22%). Artificial fish food was the highest in the diet of M. piceus during autumn (39%), decreased in summer (22%) until disappeared during spring. It reached highest level in diet of C. idella during autumn (49%), decreased in spring (38%) and reached lowest proportion during summer (21 %).

Correlation between snails and fish in fish ponds of World Fish Center (ICLARM) with special reference to snail vectors of schistosomiasis and fascioliasis.

The abundance of snail species in earthen fish ponds, irrigation and drainage canals at World Fish Center (ICLARM) in descending order was Bellamya unicolor (50.89%) > Physa acuta (18.94%) > Cleopatra bulimoides (7.6%) > Lanistes carinatus (6.73%) > Bulinus truncatus (5.19%) > Melanoides tuberculata (4.83%) > Lymnaea natalensis (3.14%) > Gabbiella senaariensis (0.9%) > Biomphalaria alexandrina (0.55%) > Lym naea truncatula (0.4%) > Planorbis planorbis and Succinea cleopatra (0.33%) > Ferrissia isseli (0.18%). Dead snails constituted about 5.19% of all the collected specimens. There were dramatic decrease in the total number of pulmonates in fish ponds which contained only Tilapia sp., and a very small number of cat fish, whereas the numbers of prosobranchia snails were much higher in these ponds. In fish ponds which accommodated a variety of fish species, the most dominant snail was B. unicolor followed by L. carinatus. However, pulmonate snails were absent in these ponds. B. truncatus was the only snail species found in concrete tank which contained only young tilapias with a very small size (5-8 cm in standard length). In irrigation canals, the number of snails and diversity was much higher than those in fish ponds. Out of 191 snails collected from inlet irrigation canal, 71 were dead, but in the outside irrigation canals, seven out of 564 snails were dead. P. acuta was absent in all examined fish ponds, but it was alive and in a high number (497 snails) in the outside irrigation canals. The number of snails collected from Bahnasawy drain was remarkably low (128 snails), however the diversity of snails was much higher compared to those in fish ponds and irrigation canals. Snail populations were stable with constant recruitment of young to adult snails for all the studied species.

Molluscicidal effect of fungicide, herbicide and plant extract on some biological and physiological parameters of Biomphalaria alexandrina.

In was found that the exposure of B. alexandrina to LC25 of fungicide (Isoprothiolane), herbicide (Anilofos) and plant extract (Euphorbia lactea) led to highly significantly elevated in the number of abnormal egg masses laid by treated snails in comparison with the control ones. The LC25 caused reduction in infection rate of B. alexandrina. It caused reduction in number of cercariae per snail during the patent period and reduction in the period of cercarial shedding. The results obtained showed that adenosine triphosphatase (ATPase) activity of tissue of snails was significantly increased in response to tested substances. The activity level of lactate dehydrogenase (LDH). pyruvate kinase (PK) and phosphoenolpyruvate carboxy kinase (PEPCK) was significantly reduced in response to treatment. This reduction does not reflect on both D. lactate and pyruvate concentrations.