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Regardless of the absence of spinal deformities, vitamin C deprivation in adult-sized Clarias gariepinus challenged the physical integrity and survival of ®sh, inducing changes that greatly resembled those of ®ngerlings of other species. Vitamin C was presumed to be a dietary facilitator, which when deprived in the diet of C. gariepinus, would obstruct intestinal absorption of iron and/or impair its release from the reticulo-endothelial stores. This impaired erythrocyte synthesis led into anaemia (as indicated by lowered levels of red blood cells, haemoglobin and haematocrit). Leukopenia noted in ®sh on a scorbutic (lacking vitamin C) diet suggested functional depression of phagocytic engulfment with increased susceptibility to the deteriorating action of pathogenic agents. Changes in histology included hypertrophy, oedematous separation and telangiectasia of gill lamellae. Shrunken glomeruli, sloughed Bowman's capsules and tubular dilation and distortion were also shown. Shrunken hepatocytes and the occurrence of yellowish ceroid pigments were the concrete histopathological signs in liver. Vitamin C is thus suggested as a potent antioxidant that oers protection against oxidative damage to various ®sh tissues. KEY KEY WORDS

Carbonate commonly accumulates in weathering profiles developed on noncalcareous parent material under arid and semiarid climatic conditions. Such weathering profile types are widespread in Morocco, making it critical to know the sources of the calcium in order to understand the genesis of carbonate‐rich soils. In this study, we use 87Sr/86Sr as a geochemical tracer of the Ca sources in weathering profiles developed on volcanic rocks (basalt, tuff, andesite and latite) in the Mediterranean coast of Morocco. The results show that the most of the Sr, and hence Ca, is of an external origin, derived from (i) sea‐water for the profiles located near to the coast or (ii) sea‐water plus Liassic carbonate outcropping in the catchment for the profiles more distant from the coastline. The contribution of the host rock is small, being less than 25%. The ratio of the Sr (Ca) from the parent material to that from the external sources is controlled by the degree of porosity developed in the profile.

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Huge amounts of rice straw are left every year in different areas of the world; these residues still cause environmental problems due to un-safe practices such as burning. Isolation of nanomaterials such as cellulose nanofibers represents an effective way for utilization of rice straw in advanced products. The current work aimed at evaluating the properties of rice straw cellulose nanofibers isolated from bleached and high-lignin unbleached pulps using a multi-criterion quality index, which allows a benchmarking analysis between different sources, processes and features. Rice straw was subjected to neutral sulfite pulping process to obtain the high-lignin unbleached pulp while the bleached pulp was obtained by bleaching the produced pulp with NaClO2/acetic acid mixture. Using mechanical pretreatment (Valley beater), and ultrafine friction grinder both bleached and unbleached pulps were used to obtain cellulose nanofibers with and without lignin (LRSNF and RSNF, respectively). Nanopaper sheets were prepared from both types of nanofibers and characterized using tensile tests, optical microscopy, atomic force microscopy, electron scanning microscopy, water contact angle and surface energy. Cellulose nanofibers generated from rice straw were scored using a multi-criterion quality index depending on characterization using eight tests (nanosized and macro size fraction, turbidity, Young's modulus, porosity, transmittance, tear resistance, and homogeneity).