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Abstract
The present work deals with myxosporidian and helminth parasites infecting the internal organs of four genera and five species of Nile fishes in Assiut Province. The examined fishes were Bagrus bayad, Bagrus docmac, Synodontis schall, Oreochromis niloticus and Lates niloticus. Specimens were collected during the period from 2001 to 2002 from the River Nile at Assiut Province. The thesis includes the following chapters :
Chapter I : deals with the general survey which includes examination of 300 freshwater Nile fishes. It was found that the incidence of myxosporidian parasites infection 44.6% while the incidence of helminth parasitic infection was 58.3%.
Seasonal variations indicated that no single pattern was observed controlling the incidence of infection with both of myxosporidian or helminth parasites among the different seasons.
Chapter II : In this chapter 12 species of myxosporidian parasites were described belonging to three genera Henneguya, Myxobolus and Unicauda and one family Myxobolidae. Two species of Henneguya were described; the first species was described from Lates niloticus and studied
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using light, scanning and transmission electron microscopes. The second one was described from Synodontis schall and not identified on the specific level, owing to its rare incidence and low intensity of infection.
Nine species of Myxobolus were described, four of which were redescribed. These were Myxobolus heterosporea Baker, 1963, Myxobolus brachysporea Baker, 1963, Myxobolus synodonti Marwan, 1980 and Myxobolus clarii Mandour et al., 1993. The other five species of Myxobolus were described and proposed to be new species and named as Myxobolus oreochromi, Myxobolus ovali, Myxobolus sphericulata, Myxobolus brushi and Myxobolus knobL
One species of Unicauda was redescribed which was Unicauda nilotica El-Naffar, 1970.
Chapter III : deals with the histopathological effects of some myxosporidian parasites using light microscopy. Histopathological effects were observed in the kidney, spleen and liver of Qeeochramis niloticus and gills and intestine of Lates niloticus. This study revealed the following :
Parasitic infection in the Kidney lead to disorders in the capillary tuft of glomeruli beside infilteration of the red blood corpuscles. The renal tubules exhibit histopathological effects as mechanical pressure due to the presence of parasitic cysts between them and degeneration features of the epithelium lining of these tubules. Also, aggregations of lymphocytes, melanomacrophge centers and congested blood vessels were observed in the infected kidney.
Histopathological effects in the spleen were observed as aggregations of melanomacrophage centers and lymphocytes at the infected areas.
In the Infected liver, pyknosis of hepatocytes nuclei and dissociation of hepatic cords were observed within the hepatic tissues.
The infected gills exhibit some defects such as cartilage destruction of the gill filaments, aggregations of lymphocytes, bronchitis, lamellar fusion and necrosis of the secondary lamellae in some cases.
In the infected intestine, aggregations of lymphocytes and macrophage cells were observed in mucosa layer where the parasite existed.
Chapter IV : deals with the description of some helminth parasites found in examined fishes which includes description of four trematodes, one cestode, four nematodes and two acanthocephalan parasites.
Four trematodes were redescribed belonging to four different families. These were Haplorchoides cahirinus (Looss, 1896) Looss, 1899, Acanthostomum (Acanthostomum) spiniceps (Looss, 1896) Looss, 1899. Astiotrema impletum var. aspinocephala Abdel-Maksoud. 1988 and metacercaria of Clinostomum phalacrocoracis ’Dubois, 1931. Haplorchoides cahirinus (Looss, 1896) Looss. 1899 was studied for the first time using scanning electron microscopy to show the surface features of this parasites.
The cestode, Wenyonia virilis woodland, 1923 was redescribed and studied using scanning electron microscopy.
Four nematodes were redescribed which were Procamallanus laevlconchus (wedl, 1862, Baylis, 1923), Procamallanus (Spirocamallanus) spiralis (Baylis, 1923, Boomker, 1993), Spironoura verebekei Campana-Rouget, 1961 and Cithariniella sp. The first species, Procamallanus laeviconchus (wedl, 1862, Baylis, 1923) was redescribed and studied for the first time by using scanning electron microscopy.
Two acanthoeephalan parasites were redescribed and studied for the first time by using scanning electron microscopy to show the external features of both parasites. The first species was Rhadincrhynchus niloticus Mohamadain, 1989, while the second one was Acanthogyrus (Acanthosentis) tilapiae Baylis, 1947.