Potential health risk assessment of some bioaccumulated metals in Nile tilapia (Oreochromis niloticus) cultured in Kafr El-Shaikh farms, Egypt.

In Egypt, using agricultural drainage water is a serious challenge for fish farming, due to water scaristy. Metals could be a potential threat to the quality of the cultured fish. Thus, this study aimed to assess the content of the metals in the cultured fish, their effect on the fish tissues, and the possible human health risk upon their consumption. This accomplished firstly, by determining the levels of essential Fe, Mn, Zn, Cu, beside the top three most toxic metals (Cr, Cd, and Pb) in the edible muscles and liver of 200 samples of Oreochromis niloticus cultured at three fish farms, using inductively coupled plasma optical emission spectroscopy (ICP-OES). The results showed the order of abundance: Fe > Zn > Cu ≥ Cr > Mn > Pb > Cd. Levels of Fe, Zn, Mn, and Cu in the fish liver were higher than corresponding values of muscles by 3, 3, 5, 9 order of magnitude, respectively. The histopathological examination showed alternations in muscles and liver tissues of fish farms irrigated with drainage water. However, the risk assessment indicated the safe human consumption of cultured fish produced from these fish farms.

A review article on nanotechnology in aquaculture sustainability as a novel tool in fish disease control.

In recent decades, aquaculture has played a significant role in fulfilling the vast demand for animal protein requirements and consequently in food security. However, environmental contamination and disease prevalence are considered essential challenges for the sector. In this regard, new approaches have been paved in technology to deal effectively with such challenges. Among these, nanotechnology-as a novel and innovative tool-has a broad spectrum of uses and a tremendous potential in aquaculture and seafood preservation. It can provide new technologies for management of drugs as liberation of vaccines and therefore hold the assurance for civilized protection of farmed fish against disease-causing pathogens. This article presents a review of nanotechnology and its applications in aquaculture. Additionally, it gives a brief idea about the fish disease and classical ways of controlling pathogens. On the other hand, this review sheds the light on nanotechnology as a potential novel tool which may possibly enhance the management and the control of disease prevalence. Therefore, the importance of this technology to promote sustainable aquaculture has also been highlighted. Focusing on the role of selenium nanoparticles as an efficient element is discussed also in this article.

Sexual patterns and protogynous sex reversal in the rusty parrotfish, Scarus ferrugineus (Scaridae): histological and physiological studies.

Gonadal histology confirmed that Scarus ferrugineus is a diandric protogynous fish. The process of protogynous sex reversal was investigated through histological observations on the gonads of females changing sex to male. This process was divided into three stages on the basis of changes in the structure of the germinal and somatic elements. Ovaries of functional females (stages IV-V) were filled with vitellogenic oocytes during the breeding season but contained no trace of spermatogenic tissue. During post-spawning period, the remaining vitellogenic oocytes began to degenerate and accompanied by a drop in plasma levels of estradiol-17ß. At the commencement of sex change, previtellogenic oocytes began to degenerate and stromal cell aggregation was observed in the central region of the lamellae. At mid-reversal stage, steroid-producing cells (Leydig cells) developed at the border of the stromal aggregate and spermatogonial cysts appear at the periphery of lamellae. Finally, sex change to secondary males was considered complete, with the beginning of active spermatogenesis and spermiation. Plasma levels of testosterone remained low throughout the sex change, but II-KT increased rapidly parallel to the increased number of Leydig cells while the level of estradiol-17ß decreased. The results indicate also that the sex-changed males had higher level of II-KT than primary males, while primary males had higher level of testosterone. Histological examination revealed that testes of primary and secondary males are almost identical in organization of the spermatogenic cysts, association of sertoli cells, and developing germ cells but differ in clustering and development of Leydig cells.