Balanced aquafeed is the key factor for enhancing the productivity of aquatic animals. In this context, aquatic animals require optimal amounts of lipids, proteins, carbohydrates, vitamins, and minerals. The original plant and animals’ ingredients in the basal diets are insufficient to provide aquafeed with suitable amounts of minerals. Concurrently, elements should be incorporated in aquafeed in optimal doses, which differ based on the basal diets’ species, age, size, and composition. Selenium is one of the essential trace elements involved in various metabolic, biological, and physiological functions. Se acts as a precursor for antioxidative enzyme synthesis leading to high total antioxidative capacity. Further, Se can enhance the immune response and the tolerance of aquatic animals to infectious diseases. Several metabolic mechanisms, such as thyroid hormone production, cytokine formation, fecundity, and DNA synthesis, require sufficient Se addition. The recent progress in the nanotechnology industry is also applied in the production of Se nanoparticles. Indeed, Se nanoparticles are elaborated as more soluble and bioavailable than the organic and non-organic forms. In aquaculture, multiple investigations have elaborated the role of Se nanoparticles on the performances and wellbeing of aquatic animals. In this review, the outputs of recent studies associated with the role of Se nanoparticles on aquatic animals’ performances were simplified and presented for more research and development.
SUMMARY:In the present study, we focused on the morphology of L. sceleratus gills using gross anatomy, scanning electron microscopy as well as light microscopy. Results of this study revealed that the gill openings appeared as simple slits anterior to the pectoral fin without distinct opercular cover. The gill system consisted of three pairs of gill arches carrying two rows of gill rakers on its concave border and gill filaments on its convex border. SEM showed that all surfaces of the gill arch were characterized by the presence of the longitudinal ridges with many taste buds in addition to many spines around the rakers. Histologically, the gill arch was composed of curved bar of hyaline cartilage with slightly elevated area corresponding to the sites of gill rakers. Each filament was formed of a thin central cartilaginous core surrounded by peripheral cartilaginous ma trix and covered by primary epithelial layer with abundant mucous cells. The chloride cells appeared mainly near to the base of secondary lamellae. Each gill filament gave rise to a very large number of secondary lamellae on both sides. The epithelial lining of the secondary lamellae comprised epithelial pavement cells, few mucous cells and pillar cells. The latter interposed the enriched blood capillaries. These findings suggest that L. sceleratus gills have characteristic morphological features that are related to adaptive functions for feeding habits, osmoregulation and respiratory mechanism with in their living environment.
The present study was carried out on the oropharyngeal cavity of the hooded crow to investigate the gross and microscopic structures via gross anatomy, light microscopy and scanning electron microscopy (SEM). The gross anatomy clarified the elongated triangular shape of the oropharyngeal cavity with a non‐protruding tongue with a bifid apex. The lingual body contained median groove rostrally and separated caudally from the root by a transverse papillary crest. The laryngeal mound located posterior to the lingual root, contained midline laryngeal cleft and bounded caudally by a transverse row of pharyngeal papillae. The palate contained choanal cleft rostrally and infundibular slit caudally in addition to five palatine ridges. By light microscopy, the dorsal lingual epithelium was highly keratinised stratified squamous with a lingual nail in the most rostral part of the apex. Then, the thickness of the keratin layer decreased caudally, while in the ventral surface, the lining epithelium became non‐keratinised. The entoglossum supported the lingual body and root, but not extended to the apex. The lining epithelium of the palate was also keratinised stratified squamous and became none‐keratinised at the oral side of the choanal cleft. There were numerous lobules of polystomatic salivary glands in the lingual root and the palate. SEM revealed the arrangement of different types of papillae covering both the floor and the roof of the oropharynx besides numerous openings of salivary glands in the lingual root, laryngeal mound and the palate. These findings reflect the functional relationship of the oropharyngeal cavity of the hooded crow during feeding.
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