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Abstract V - SUMMARY Freshwnter invertebrates have a great economic importance either as a source of protein for man (as cn~stacea) or as a source of food for fishes and edible Crustacea (as zooplankton and other invertebrates). Furthermore some these freshwater invertebrates are parasites which cause diseases for several aquatic animals either vertebrates or invertebrates. Also, other species act as intermediate . . hosts for parasites infecting man, wild and domestic animals, birds and fishes. In spite of the above mentioned economic importance, the taxonomical and morphological studies on the Egyptian freshuiater invertebrate fauna are insufficient and covers only very small parts of the taxa, and Therefore this thesis was planned in an attempt to fill this shortage. The study is divided into two main parts. The first part contains a detailed taxonomical investigation of freshwater invertebrate fauna inhabiting some water bodies in Gharbia and Menoufia governorats. Keys and descriptions of the recorded specces as well as redescriptions were submitted with the aid of scanning eletron microscope. The second part includs some ecological observation on the recorded taxa including dominancy population density and seasonal distribution. . . The sa~nples were collected monthly from each of four sites in Delta provience (Two sites in Gharbia governorate and two sites in Menoufia govcrnorate) through n period of two years extending from December 1988 till November 1900. Each sample consisted of a single vertical net haul at the sampling site. Meanwhile, with each collection, temperature of water and air were measured. Other sites of collecrion were taken once either to search for large Crustacea as shrimp and crab (Rahr Shebin Canal) or to determine the density of freshwater invertebrate fauna in polluted area (drain behind the ice factory in Tan t a). The large samples such as leeches, Molluses and decapods which are attached to stones, plants stems and floating leaves were hand-picked for the investigation. The main results of this study could be summarized as follow : - 1 - Taxonomy : The recorded species were 27 in number belonging to seven phyla. Among these, 14 species are large and hand - picked. These species are Barbronia assiuti; Salijb perspicax; Helobdella conifera (Nirudinea : Annelida); Neritina nilotica; Viviparn utzicolm-, Lanistes boltetzi; Cleopatra bulitnoides; Lytnlnaeu tnitzcat~rla; Bulitz~is trwzcatus; Bio~npl~daria alexatzdritza; plzysa acuta; Sphueriutn sitnile (Molluscs) atzd Potarnotzautes tziloticus (Crustacea). The other 13 species are planktonic ind collected by the net. These are Hydra viridis; Hydra vulgaris (Hydrozoa : Cnidar-ia); Mesostoma orabiensis (Turbellaria : Platyhelminthes), Brachion~is ~irceolaris (Rotifera), Dorylainzus fecundus (Nematoda); Pristina sp., Nais sp. (Oligochaeta : Annelida), Ceriodaphnia reticulata, Sitnoceplzalus exspitlosus, Si11zoceplza1~i.s ver~ilus (Brnnchiopoda : Crustacea). Cypretta bilicis, Cl~lutnydotlzeca texasiensis (Ostracoda : Crustacea) and Cyclops vernalis (Copepoda : Crustacea). Among detected sample 8 species are firstly recorded in Egyptian freshwater. These species are H. viridis, H. vulgris, D. fecundus, Pristina sp. Nais sp., Cypretta bilicis, C. texasiensis and C. vernalis . 2. Ecology : It has been found from the data, that the species of Copepoda and Cladocera . . are the most domitiant members in all sites of collection while the species of Ostracoda and Turbellxia are the least dominant members. The relatively low densities of Kotifera recorded here might be due to the cleaning of the investigated water bodies during late sping and early summer in both years of investigation. The species of Rotifera, B. ~irceolnris, was found to be dominant at sites 2 and 4. On the other hand, the species of Copepoda (C. vernalis ) and Nematoda (D. fec~rndi~s ) weie’found to be dominant at all sites of collection except at site 4. Moreover, the turbellarian species and Nais sp. were found to be subdominant in - all the investigated sites. The ostracode species, C. texasiensis was found to be subrecedent at site 3. The ecological parameters used have reveale that the species composition of the invertebrate zooplankton community at the studied sites was more or less similar. This may be due to the close similarity of the prevailing anvironmentnl factors during this study. The effect of silt, clay, mud and salinity on the susceptibility of Nais sp. and Physa aclltcl to Cd C12 concentrations was also studied. The applied solutions were changed every 24 hours. The volume of the solution depended upon the number and size of the animals i.e. 1 ml and 2 ml of solution for each individual of Nais sp. and P. acuta, respectively. The concentrations of Cd C12 used were 1, 1.5, 2.5, 5 and 10 ppm and the quantities of silt, clay or mud used . in the experiments were 0.2, 0.4, 0.6, 0.8 and 1 gm. The present data demonstrate that Nais sp. shows an obvious resistant against the different concentrations of Cd C12 or no obvious effect on the mortality of these worms at low levels of cadmium and there is no significant difference between the doses 1 and 1.5 ppm. Moreover, the results showed that silt amount of 0.6 gm was accompanied by higher mortalities within the first seven days of treatment after which the higher mortalities were restricted the lower quantity of silt. The statistical analysis showed a tendency to decrease the mortality as the concentration of CdC12 increased which may be produced as a result of the adsorption effect of the silt. On the other hand, there is no significant difference between the control group and any of the various quantities of clay or mud. Therefore, mortalities caused by using mud or clay with Cd C12 could be referred to the effect of Cd C12 alone. This gives indication to the importance of clay or mud in adsorbing Cd cations as a heavy metal and hence enhancing the survival of this species. The present results showed that a decrease in salinity caused an increase in the lethality of cadmium for these womx. On the other hand, the data demonstrated that the snail P. acuta is very resistant to all the concentrations of Cd C12 below 10 ppm, while 10 ppm caused death for more or less half of the tested snails at 24 hours. Moresover, Silt, Clay and mud proved no significant effect in adsorbing cadmium and hence did not influence the survival of’the snail. |