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The three main Nile Delta wetland ecosystems, Manzala, Burullus and Edku lagoons, are among the most ecologically important and productive habitats in Egypt. We studied the area degradation and the human health risks associated with trace metal accumulation in Tilapia zillii harvested from these lakes. The area of Manzala lagoon has shrunken from about 3035 km2 in 1800 to about 288 km2 in 2015, the area of Edku has shrunken from about 336 km2 in 1824 to about 18 km2 in 2014, and the area of Burullus has shrunken from about 1116 km2 in 1949 to about 546 km2 in 2014. This area degradation is attributed to drying for housing, land reclamation and fish farming. As a result, the concentration of pollutants and nutrients has subsequently increased, and large parts of the lakes have been overgrown with aquatic vegetation, which increased the rate of degradation and land transformation. Metal pollution was detected in water, sediment and edible fish harvested from the lakes. The hazard index, an indicator of human health risks associated with fish consumption, showed adverse health effects of zinc and lead metals for habitual fish consumers. The impact of the high dam on the lakes was discussed.

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Abstract:We tested the combined effect of the fungus Beauveria bassiana and the microsporidium Nosema pyrausta on the European corn borer larvae, Ostrinia nubilalis, in the laboratory. The first instar of O. nubilalis larvae was the most sensitive to the B. bassiana infection followed by the fifth, second, third, and fourth instar (LC 50 s were 4.91, 6.67, 7.13, 9.15, and 6.51 x 10 5 conidia/ml for the first to fifth instars, respectively). Mortality of each instar increases positively with concentration of conidia. When B. bassiana and N. pyrausta were used in combination, mortality increased significantly in all instars. Relative to the B. bassiana treatment alone, the B. bassiana + N. pyrausta treatment decreased the LC 50 s by 42.16%, 37.63%, 21.60%, 27.11%, and 33.95% for the first to fifth instars, respectively. The combined effects of the two pathogens were mostly additive. However, at the two highest concentrations the pathogens interacted synergistically in the first and second instar. Individuals that survived the B. bassiana and B. bassiana + N. pyrausta treatments and developed into adults had significantly shorter lifespans and females oviposited fewer eggs than non-exposed insects. The effects on the longevity and the egg production were most pronounced at high concentration of B. bassiana conidia. © Versita Sp. z o.o.

Nerium oleander (Apocynacea) is a highly toxic plant that has never been reported to be selected as a food or even as a resting place by any acridid species. The study tested the competence of Heteracrislittoralis (Orthoptera: Acrididae) to tolerate and survive on this plantfor considerable periods, and to resume normal capacity of development and reproduction when favourable food plant became available. Nymphal survival and development were followed by monitoring three cohorts of freshly hatched hoppers. The first cohort fed oleander leaves; the second one (control) fed clover; while the third cohort fed oleander leaves for 35 days, and then switched to clover. Age specific survivorship and reproductive parameters of the adults were followed by monitoring three cohorts of newly fledged adults fed on the same patterns. Moulting was suspended in nymphs fed oleander; when food plant was switched to clover, the insects resumed normal development and reached the adult stage. Adult cohort reared on N. oleander exhibited a normal age specific survivorship curve, but ovarian development was suspended. Suspension of ovarian development by N. oleander was accompanied by very low indices of food consumption and conversion of digested food into body substance. But, after switching to normal food, clover, the insects resumed normal ovarian development with significant prolonged longevity, and the fecundity was approximately equal to the same parameter in the control cohort. This reflects a strong evolutionary biotic potential against the selective power of plant defense.

Chemical pesticides are essentially hazardous. The risks differ from compound to compound, and much of the information on their actions on insect development remains to be captured. The toxicity of abamectin (a macrocyclic lactone, acting on glutamate-gated chloride channels of insects), and fipronil (a phenylpyrazole, disrupting the GABA receptors) was given on embryos of the short-horned grasshopper Heteracris littoralis (Rambur, 1838) for the first time. Abamectin is 66 times more fatal than fipronil. Treated eggs with a sublethal dose gave a reduction up to 51% in hatchability as compared with normal eggs; yet, without any effect on the incubation period. Many embryos have stopped developing at certain developmental stages. The disruptive effects of both the tested chemicals on the brain and the compound eyes were described. The brain and the compound eyes were severely disrupted. The optic lobes appear small in size, and this led to the malformed compound eyes and optic nerves. The brain cells appeared loose and perhaps few in number. The neurosecretory materials carried in the neurosecretory cells were not clear. The neuropil was wide in the normal brain rather than in treated ones. Treated embryos suffered a shrinkage in ommatidia size and number, they are also irregular. Perhaps continued and precise studies should be made to minimize resistance, usually low doses enhance. Continuing studies on the tested pesticides may provide novel insights on their actions for more effective insect control strategies.