A two-fold integrated research study was conducted; firstly, to understand the effects of copper (Cu) and zinc (Zn) on the growth and oxidative stress in Nile tilapia, Oreochromis niloticus; secondly, to study the beneficial effects of the duckweed Lemna minor L. as a heavy metal remover in wastewater. Experiments were conducted in mesocosms with and without duckweed. Tilapia fingerlings were exposed to Cu (0.004 and 0.02 mg L−1) and Zn (0.5 and 1.5 mg L−1) and fish fed for four weeks. We evaluated the fish growth performance, the hepatic DNA structure using comet assay, the expression of antioxidative genes (superoxide dismutase, SOD; catalase, CAT; glutathione peroxidase, GPx and glutathione-S-transferase, GST) and GPx and GST enzymatic activity. The results showed that Zn exhibited more pronounced toxic effects than Cu. A low dose of Cu did not influence the growth whereas higher doses of Cu and Zn significantly reduced the growth rate of tilapia compared to the control, but the addition of duckweed prevented weight loss. Furthermore, in the presence of a high dose of Cu and Zn, DNA damage decreased, antioxidant gene expressions and enzymatic activities increased. In conclusion, the results suggest that duckweed and Nile tilapia can be suitable candidates in metal remediation wastewater assessment programs.

The increase of seawater temperature as a result of global climate variation elucidates a major challenge for marine organisms survival in addition to consumers safety. Spotted grouper (Epinephelus coioides) and Seabream (Sparus aurata) were collected in water with different temperature variations at Suez Canal and Alexandria (Suez and Abu Qir bay) in Egypt with the aim to assess expression levels of heat shock proteins such as HSP47, HSP70 and HSP90 genes in addition to antioxidants value through enzymes activity: Glutathione-S-Transferase (GST) and Glutathione Peroxidase (GPx). Research results revealed that expression of the HSP47, HSP70a and HSP90 genes increased in marine fishes tissues collected from Suez Canal, with higher water temperature (23:28ºC), compared with those collected from Alexandria (19:24°C) whereas the content of GPx and GST decreased. Our results show alteration of the marker examined suggesting that the increase of heat shock protein genes expression levels of fish collected from Suez Canal might be exposed mainly to thermal oxidative stress response more than those collect from Alexandria. The increase of heat shock protein-related genes expression could be considered as a factor in prohibiting the heat shock transcription factor that may lead to stimulation of heat-inducible genes in addition to heat acclimation. Thus, warming of water is also likely to alter the composition and abundance of food resources, e.g. fish muscles, available to higher trophic level consumers.

Mediterranean fish species living along Italian (Gaeta) and Egyptian (Alexandria) coasts were analyzed using DNA barcodes for molecular identification. Mitochondrial Cytochrome c Oxidase subunit 1 (COI) gene was sequenced from 31 different marine species to test whether the morphology-based assignment of individuals into 19 families, 6 orders was supported by DNA-based species delimitation and Neighbour Joining cladogram. All COI rRNA gene barcodes were matched with reference sequences of expected species, according to morphological identification. Neighbour joining tree was drawn based on COI rRNA gene and the majority of specimens clustered in agreement with their taxonomic classification. Our results updated Mediterranean edible fish knowledge providing graphical resources, taxonomical and bioinformatics references, improving the genetic fish database and the basic molecular information to strengthen the science-policy interface for biodiversity and ecosystem services as conservation, blue economy, and long-term human well-being.

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We have developed an original in vitro bioassay using teleost scale that has osteoclasts, osteoblasts, and bone matrix as each marker: alkaline phosphatase (ALP) for osteoblasts and tartrate-resistant acid phosphatase (TRAP) for osteoclasts. Using this scale in vitro bioassay, we examined the effects of seawater polluted with highly concentrated polycyclic aromatic hydrocarbons (PAHs) and nitro-polycyclic aromatic hydrocarbons (NPAHs) on osteoblastic and osteoclastic activities in the present study. Polluted seawater was collected from 2 sites (the Alexandria site on the Mediterranean Sea and the Suez Canal site on the Red Sea). Total levels of PAHs in the seawater from the Alexandria and Suez Canal sites were 1364.59 and 992.56 ng/l, respectively. We can detect NPAHs in both seawater samples. Total levels of NPAHs were detected in the seawater of the Alexandria site (12.749 ng/l) and the Suez Canal site (3.914 ng/l). Each sample of polluted seawater was added into culture medium at dilution rates of 50, 100, and 500 and incubated with the goldfish scales for 6 hrs. Thereafter, ALP and TRAP activities were measured. As a result, ALP activity was significantly suppressed by both polluted seawater samples diluted at least 500 times, although TRAP activity did not change. In addition, mRNA expressions of osteoblastic markers (ALP, osteocalcin, and the receptor activator of the NF-B ligand) decreased significantly, as did the ALP enzyme activity. Actually, ALP activity decreased with selected PAHs and NPAHs treatments. We conclude that seawater polluted with highly concentrated PAHs and NPAHs influenced bone metabolism in teleosts.