An Overview of Metal Pollution in the Western Harbour of Alexandria,Egypt

Limited data are available on the concentration of metals in sediments in the Western Harbour of Alexandria. The most comprehensive record is from a survey conducted more than a decade ago. Industrial and human activities in and around this area have increased dramatically in the last 20 years. The purpose of this study was to determine the concentrations of heavy metals in surfacial bottom sediments of the harbor, to assess their potential biological effects and to identify their possible sources. Sediment samples from 21 stations throughout the harbor were analyzed for grain size, total organic carbon content (TOC), and metals (Al, As, Ba, Be, Cd, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Se, Sn, V, and Zn) to assess the extent of contamination in the area. The results indicated that concentrations of metals in the sediments varied widely depending on the location. High levels of metals were observed in the Arsenal Basin and the outfall area of El Mahmoudiya Canal in the inner harbor. The concentrations of metals were found to be higher than those recorded in the previous study. However, with some exceptions, most of the changes in the metal concentrations could be accounted for by the variations in aluminum, which represents the variations in mineralogy and grain size, indicating that the majority of the metals were of “natural” origin. The present data were also compared with results from other areas.     

Effects of parasitization of Trichoplusia ni by Chelonus sp.

ABSTRACT. Parasitization of Trichoplusia ni (Huebner) (Lepidoptera: Noctuidae) by Chelonus sp. (Hymenoptera: Braconidae), an egg-larval parasitoid, leads to precocious cocoon spinning of the host in the fourth (penultimate) stadium followed by parasitoid emergence from the prepupa. We have investigated the mechanism by which Chelonus sp. disrupts host development. The developing larva and fluids injected by the adult female separately from the egg, are not the source of these effects, but it remains a possibility that the teratocytes, originating from the trophamnion of the parasitoid egg, are responsible. The titre of the juvenile hormone esterase activity in the haemolymph of the parasitized fourth instar host is similar to that in the initial period of the final instar of normal T. ni, but lacks the postwandering peak of activity. The increased JHE activity leads to a reduced JH titre early in the fourth stadia. This indicates that disruption of host development occurs within 12h after apolysis to the fourth stadium, if not before. Anti-juvenile hormone activity is not detected in extracts of parasitized T. ni. The morphological and behavioural changes associated with precocious development of the T. ni host are prevented by applications of juvenile hormone I, juvenile hormone II and the juvenoid, Ro 10–3108, but not juvenile hormone III and the juvenoid R 20458. However, these applications fail to prevent the onset of juvenile hormone esterase activity, another marker of precocious development. These observations indicate that simple anti-juvenile hormone activity may not be the mechanism of disruption of host development. Development of the parasitoid is disrupted by application of Ro 10–3108 and juvenile hormones I, II and III, but timing of eclosion is only affected by application of juvenile hormone I, juvenile hormone II and Ro 10–3108. This observation may indicate a discrimination by the parasitoid between its own juvenile hormone III and the host's juvenile hormone II.     

The Fossil Record of Shell Boring by Snails

The predatory boring habit common to many recent snails probablyarose first in the Polinicinae (Naticacea) during Upper Cretaceous(Cenomanian) times (100 million years B.P.) . In the fossilrecord the frequency of bored shells increasesgreatly in rocksof latest Cretaceous age and becomes more widespread duringearly Tertiary times coincident with the major diversificationof the primary groups of boring snails. The borings in these Cretaceous and Tertiary shells show thesame characteristics of preference of penetration in one pelecypodvalve rather than the other or in position of the boring siteon the shell that are found in recent shell assemblages. Borings in Paleozoic brachiopod shells (230–550 millionyears old) that have previously been attributed to gastropodpredation are herein attributed to other but unknown boringorganisms. In part these borings are not accepted as evidence of Paleozoicgastropod predation because it necessitates: (1) Postulationof the separate development of a boring habit ith its concomitantdevelopment of an accessory boring organ in a groupwhose descendantsare all herbivores, and (2) The development of such a habithundreds of millions of years before the appearance of any relativesof present day borers.