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The global production of aquatic organisms has grown steadily in recent decades. This increase in production results in high volumes of by-products and waste, generally considered to be of low commercial value and part of them are consequently discarded in landfills or in the sea, causing serious environmental problems when not used. Currently, a large part of the reused aquaculture waste is destined for the feed industry. This generally undervalued waste presents an important source of bioactive compounds in its composition, such as: amino acids, carotenoids, chitin and its derivatives, fatty acids and minerals. These compounds are capable of offering numerous benefits due to their bioactive properties. However, the applicability of these compounds may be opportune in several other sectors. This review describes studies that seek to obtain and apply bioactive compounds from different sources of aquaculture waste, thus adding commercial value to these underutilized biomasses.HIGHLIGHTSVolume of aquaculture industrial waste from crustaceans and mollusks.Quantity and quality of bioactive components in aquaculture waste.Applications of recovered proteins, lipids, chitin, carotenoids and minerals.Future prospects for the destination of aquaculture waste.

Mast cells are important in inflammatory processes and in the nonspecific immune response, and there are also indications that these cells are associated with the effectors of the specific immune response. Eosinophilic granular cells are frequently compared to mast cells, and some authors maintain that they are the same cells. In this study, we take a fresh look at the similarities and differences between these two cell types in Oncorhynchus mykiss . We evaluated the cytomorphology of each cell type with optical microscopy, their staining affinities, and their ultrastructure. We observed that mast cells were positive for CD117 (c-kit), while eosinophilic granular cells were negative for this marker. We propose that these two cell types have certain common characteristics but represent well-differentiated populations distributed in several Oncorhynchus mykiss tissues., Competing Interests: The authors declare that there are no conflicts of interest., (© 2021 The Authors.)