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Simple Summary: The European barracuda (Sphyraena sphyraena) is a wild fish species that is both commercially and ecologically valuable and is found in the Adriatic Sea. To better understand its distribution and physiology, this study examined the digestive enzymes in various parts of the barracuda's gastrointestinal system using histochemical analyses. This is the first known study to evaluate the activity of aminopeptidase, alkaline phosphatase, acid phosphatase, and non-specific esterase in the pyloric caeca and the anterior, middle, and posterior segments of the European barracuda's gastrointestinal tract. In this study, we examined the gastrointestinal tract of the European barracuda (Sphyraena sphyraena) living in the Adriatic Sea near Dubrovnik, Croatia. The study aimed to identify the presence and distribution of four digestive enzymes: alkaline phosphatase, aminopeptidase, acid phosphatase, and non-specific esterase. We found that alkaline phosphatase activity was present in the brush border of the enterocytes in all the investigated intestinal segments. The activity of the alkaline phosphatase was the strongest in the pyloric caeca but strong only in the basal part of the intestinal villi in the anterior and middle intestinal segments. In the posterior intestinal segment, alkaline phosphatase had strong activity along the entire villi. The activity of acid phosphatase was weak in all the investigated parts of the intestine, except in the posterior part, where it was moderate. Aminopeptidase was detected in the brush border of the intestinal epithelium, with stronger activity in the pyloric caeca and anterior part of the intestine and weaker activity posteriorly. The activity of the non-specific esterase was moderate in the pyloric caeca and anterior part of the intestine, while it was weak in the posterior segment and the lamina propria in all parts of the digestive tract. Weak acid phosphatase activity was observed only in the lamina propria of the posterior part of the intestine. This study is the first to evaluate the activity of digestive enzymes in the European barracuda. [ABSTRACT FROM AUTHOR]

Simple Summary: Diptera are rich in species, contribute significantly to plant diversity, and have the potential to assess habitat health. They also include many agricultural and forestry pests. Our study provides baseline information on Diptera and Vespidae diversity in the Mediterranean mosaic of agroecosystems. Additionally, we summarized the information on the importance of human influence on Diptera diversity. We carried out an inventory of Diptera in Croatia using a set of traps placed in the proximity of honeybee hives. We determined the presence of pests and newly introduced species. A total of 94 species belonging to 24 families were recorded, including 7 important agricultural and forest pests of Diptera and 17 new records for Croatia. Results pointed out that total insect species richness, pest species richness, and the first findings depend on human activities. Furthermore, the number of honeybee colonies was negatively correlated with total species richness, while anthropogenic influence was positively correlated with pest species richness. Diptera, with their participation in pollination, significantly contribute to the maintenance of plant diversity, and they also have great potential for assessing habitat health and preserving it. A decline in their abundance and diversity has been recorded worldwide as a consequence of biotic, abiotic, and anthropic alterations. In addition to pollinators, these orders include agricultural and forestry pests, which are a threat to both cultivated and wild plants that are very important to the economy. Many pests have escaped from their native areas, and it is important to monitor their spread to implement sustainable means of control. Our study provides baseline information on Diptera and Vespidae diversity in the Mediterranean mosaic of agroecosystems, giving information on the importance of human influence on insect diversity. We carried out an insect inventory in Istria, Croatia, using a set of traps placed in the proximity of beehives. This study was also important in determining the presence of pests and newly introduced species. A total of 94 species from 24 families were recorded—7 important agricultural pests of Diptera and 17 new records for Croatia. The correlation between species diversity and environmental and anthropogenic factors leads to the conclusion that total insect species richness, pest species richness, and the first findings depend on human activities. The number of honeybee colonies negatively correlated with species richness, while anthropic influence positively affected total and pest species richness. [ABSTRACT FROM AUTHOR]