الفهرس 
ACKNOWLEDGEMENTSOnly 14 pages are availabe for public view
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Abstract
Ultraviolet (UV), one of the components of solar
radiation, is divided into UV-A (320–400·nm), UV-B (280–
320·nm), and UV-C (200–280·nm). Normally, stratospheric
ozone reflects UV-C and most of the UV-B, so only UV-A and a
little of the UV-B reach the Earth. Organisms on Earth are
therefore evolutionarily adapted to UV-A, but might not be
adapted to UV-B. Recently, due to atmospheric ozone depletion,
a great deal of attention has been focused on UV-B induced
photo damage to organisms.
Under normal conditions, many vertebrates and
invertebrates can protect themselves from UV by skin pigments
or integuments, such as feathers, hairs or scales the increasing
UV-B radiation has influenced organisms and ecosystems on
Earth. Many studies have demonstrated that enhanced UV-B
radiation may be a threat to many organisms, also in aquatic
ecosystem. Effects caused by UV-B, including DNA damage
melanogenesis, skin erythema, skin cancer, immunosuppression
and damage to the eyes, have been studied in vertebrate. UV-B
also affects egg hatching and causes deformities in amphibian
and fish embryos .Although the damaging effect of UV-A on
organisms is less than that of UV-B, the influences of UV-A also
need to be considered. Thus, it is equally important to know the
effect of UV-A and UV-B on organisms.Leeches are common in a wide range of fresh water habitat
in Egypt. This makes them one of the most suitable bio-indicator
organisms for testing UV-A. Reviewing of the literature on the
subject revealed a lack of information on the relationships
between the UV stress changes in the different biochemical
components of leeches. Since The biology and ecology of the
leech B. assiuti has attracted considerable attention. But not its
biochemistry. The present study reports the results of such
investigation carried out in that direction.
Molecular markers of the biological effects of
contaminants on organisms (i.e. biomarkers) could be used as
diagnostic and prognostic early-warning tests to detect and
assess the effects of stressors and contaminants, on
environmental quality. The results of numerous studies lead to
the hypothesis that UV may affect either the biotransformation
or oxidative stress defense systems in Barbronia assiuti. The
toxicity tests available for fresh water fauna have been restricted,
until now, to acute toxicity and chronic bioassays (i.e. growth
and reproduction).
The present study aimed to elucidate negative impact of
UV-A on the histology and histopathology of the body wall,
epidermis, muscles, pigments, botryoidal tissue and reproductive
organs, some biochemical parameters and genetic background of
Barbronia assiuti.Mature Barbarona assiuti (weight 0f 0.8-1.g) were hand
picked from irrigated canals and the River Nile at Assuit, Egypt.
Leeches were classified into four groups: control and three
UVR- A irradiated groups (first exposed for 30 min/day),
(second for 45 min/day) and (third for 60min/day) each for 15
days.
The first experiment was carried out to study the effect of
ultraviolet radiation on histology and histopathology of B.
assiuti. The results demonstrates that the irradiated groups
exhibited clear damage of cuticle, epidermis, muscle, botryoidal
tissues, gland, and reproductive tissues.
The second experiment was carried out to study the effect
of ultraviolet radiation on some biochemical parameters:
glucose, triglycerides, HDL, LDL, proteins, cholesterol and iron
where significant decrease were found in all parameters.
The third experiment was carried out to study the effect of
ultraviolet radiation on DNA of leeches. Some banding pattern
obtained for different primers used in these experiments
indicated that, significant variation in DNA bands of B. assiuti
attributed to UV irradiation.