الفهرس 
LITERATURE REVIEWOnly 14 pages are availabe for public view
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Abstract
The cattle egrets (Bubulcus ibis) are cosmopolitan species of birds in the family Ardeidae. Cattle egrets are free-range migratory birds with widespread distribution. Parasites infecting migratory birds all over the world are still under investigation. The identification of parasitic taxa infecting ardeids was done concerning their morphological and morphometric features. Parasites represent a biological marker of the host’s eating habits. Therefore, the present study aimed to provide more information on helminth parasites of the cattle egrets and these parasites’ capacity to accumulate heavy metals to be useful bio-indicators for environmental pollution or not.
A total of 20 Bubulcus ibis (Ardeidae) specimens were collected from the agricultural lands belonging to the Faculty of Agricultural at Cairo University and investigated for parasitic infections. Examination of the investigated cattle egret reported the natural occurrence of two nematode species belonging to two different families. There are different prevalence rates for parasitic species with specific infection sites in the cattle egrets: Heterakis gallinarum (family Heterakidae) infecting the lumen of the ceca with 40%, and Desportesius invaginatus (family Acuariidae) infecting the gizzard of egrets with 65%.
At morphological and morphometric levels, the adult parasitic species of H. gallinarum has all the generic features within the genus Heterakis. It could be distinguished from other species within this genus by male worms, especially by the spicule structures and lengths, number and position of the caudal papillae, the presence of the precloacal sucker, and its relative length to the cloacal aperture. Regarding the descriptions of many heterakid species that are not very precise, molecular phylogenetic analysis based on 18S rRNA and COI genes was chosen and analyzed to investigate the phylogenetic affinities and taxonomic status of the recovered parasite species. The phylogenetic analyses showed a well-resolved distinct clade for the present heterakid species with other taxa of the family Heterakidae and deeply embedded within the Heterakis genus.
At morphological and morphometric levels, the adult parasitic species of D. invaginatus has all the generic features within the genus Desportesius. It could be distinguished from other species within this genus by the body length, the margins of the tips of the two recurrent cordons are anastomosed on both ventral and dorsal surfaces with the other cordon, presence of 20 spines in the widest cuticular plates of cordons, length of the muscular and glandular esophagus, the length of the spicules (right spicule is longer than the left one), and the arrangement of the caudal papillae (four pairs of preanal and five pairs of postanal papillae). Regarding the descriptions of many acuariid species that are not very precise, molecular phylogenetic analysis based on the 18S rRNA gene was chosen and analyzed to investigate the phylogenetic affinities and taxonomic status of the recovered parasite species. The phylogenetic analyses showed a well-resolved distinct clade for the present acuariid species with other taxa of the family Acuariidae and deeply embedded within the Desportesius genus.
To assess the relationship between pollution and parasitism, the concentration of some elements was detected in both parasitic taxa and their host tissues. The bioaccumulation of different metals in different organs was higher in non-infected egrets than in infected ones. This study compares and highlights the accumulation potential of two nematode species. The bioconcentration factors obtained for the almost metals confirmed the high accumulation capacity of parasites for any pollutant than egret tissues. It confirmed that egret nematodes could be regarded as useful bio-indicators when evaluating terrestrial ecosystems’ environmental pollution by heavy metals.