Titanium dioxide nanoparticles (TiO 2 NPs) are the most produced nanomaterial for food additives, pigments, photocatalysis, and personal care products. These nanomaterials are at the forefront of rapidly developing indispensable nanotechnology. In all these nanomaterials, titanium dioxide (TiO 2 ) is the most common nanomaterial which is being synthesized for many years. These nanoparticles of TiO 2 are widely used at the commercial level, especially in cosmetic industries. High usage in such a way has increased the toxicological consequences of the human population. Several studies have shown that TiO 2 NPs accumulated after oral exposure or inhalation in the alimentary canal, lungs, heart, liver, spleen, cardiac muscle, and kidneys. Additionally, in mice and rats, they disturb glucose and lipid homeostasis. Moreover, TiO 2 nanoparticles primarily cause adverse reactions by inducing oxidative stress that leads to cell damage, inflammation, genotoxicity, and adverse immune responses. The form and level of destruction are strongly based on the physical and chemical properties of TiO 2 nanoparticles, which administer their reactivity and bioavailability. Studies give indications that TiO 2 NPs cause both DNA strand breaks and chromosomal damages. The effects of genotoxicity do not depend only on particle surface changes, size, and exposure route, but also relies on the duration of exposure. Most of these effects may be because of a very high dose of TiO 2 NPs. Despite increased production and use, epidemiological data for TiO 2 NPs is still missing. This review discusses previous research regarding the impact of TiO 2 NP toxicity on human health and highlights areas that require further understanding in concern of jeopardy to the human population. This review is important to point out areas where extensive research is needed; thus, their possible impact on individual health should be investigated in more details.

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Photoperiod and shelter have direct or indirect effects on phenotypic traits expression in different fish species. The present study was, therefore, intended to explore whether these light and shelter could influence some phenotypic traits of African catfish larvae under laboratory condition. Newly hatched larvae were stocked in plastic aquaria (10L) at a rate of 5 individuals/L and reared for one month under four treatments such as 24h light (24L), 24 h dark (24D), 12h light and 12h dark with PVC (12DL_PVC), and 12h light and 12h dark without PVC (12DL) conditions. A total of 108 larvae were sampled for phenotypic traits analysis. The results revealed that complete darkness (24D) significantly improved the overall growth parameters (total length, standard length, caudal peduncle length, anal fin length, caudal fin length, total body depth, dorsal fin length, pre dorsal distance, pre anal distance, pre ventral distance, head width, head length, eye diameter, maxillary barbell length, inter orbital length, and specific growth rate) than all other treatments, while no significant variation was found among other treatments. Although shelter did not show any significant role in the overall growth, it significantly reduced the larval mortality than those reared without shelter. The survival rates were also significantly different among various light regimes in which the highest was found in 24D (86%) followed by 12DL_PVC (74%), 24L (71%), and 12DL (60%). The study also revealed that larvae reared in 24D exhibited maximum dark brown body colouration (63%), while in 24L showed maximum light brown colouration (96%). On the other hand, maximum larvae were appeared as medium brown color (76%) in tanks having PVC, whereas many of them were light brown (61%) in non-PVC tanks. Taken together, the study suggests that C. gariepinus larvae should be reared in completely dark condition to enhance their overall production.

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