In this study, we investigated the effect of queen caging on honey bee colonies’ post-treatment development and the optimal timing of method application on honey production during the main summer nectar flow. We conducted the study in nine apiaries (N = 9) across six Mediterranean countries, with a total of 178 colonies. The colonies were divided into three test groups: QC1, QC2, and C. The QC1 group involved queens caged for a total of 28 days before the expected harvesting day. In the QC2 group, queens were caged for 28 days, but only 14 days before the expected harvesting day. The C group consisted of queens that were not caged, and the colonies received common local treatments. In both the QC1 and QC2 groups, the colonies were treated with a 4.2% oxalic acid (OA) solution by trickling after the queen release. Our findings revealed no significant adverse effects (p > 0.05) on colony strength at the end of the study resulting from queen caging. However, significantly lower amounts of honey were extracted from the QC1 group compared to both the QC2 group (p = 0.001) and the C group (p = 0.009). Although there were no initial differences in Varroa destructor infestation between the groups, ten weeks later, a significantly higher infestation was detected in the C group compared to both the QC1 group (p < 0.01) and the QC2 group (p = 0.003). Overall, our study demonstrates that queen caging, in combination with the use of OA, is an effective treatment for controlling V. destructor. However, the timing of caging plays a crucial role in honey production outcomes.

Populations of northern pike (Esox lucius) and pumpkinseed (Lepomis gibbosus) from the Mrežnica River were found to be infected with the tapeworm Triaenophorus nodulosus. In both species, the mean intensity of infection was low, suggesting a well-balanced host–parasite relationship. This study investigates pathological changes caused by adult T. nodulosus in its definitive host, the northern pike, and the associated intestinal immune response. The infection had no detectable adverse effects on either the northern pike population or the host’s body condition index. Histological examination revealed lesions both at the site of tapeworm attachment and in areas adjacent to the free strobila, involving the lamina propria and submucosa. A moderate, multifocal, ulcerative, and necrotizing enteritis was observed, accompanied by an increased number of mast cells (MCs), which were identified as the predominant immune cells involved in the E. lucius–T. nodulosus interaction. MCs, mostly degranulated, were found in the lamina propria and superficial submucosa at the attachment site. Immunofluorescence revealed a subpopulation of piscidin 1-positive MCs in the same layers, with a higher number at the attachment site compared to unaffected intestinal areas. This represents the first evidence of piscidin 1 involvement in intestinal host defence against cestode infections in teleosts.

The small-spotted catshark and the smooth-hound are cartilaginous, carnivorous fish with similar depth ranges in their habitats. These two species are among the most abundant elasmobranchs in the Adriatic Sea and are frequently caught by local fishermen using longline fishing. Despite their ecological similarities, little is known about the physiological differences in their digestive processes. The study of enzymatic digestion in these ecologically relevant species helps to fill the knowledge gap in the understanding of nutrient processing in cartilaginous fish. Therefore, the aim of this study was to determine, measure and compare the enzymatic activity of alkaline phosphatase, acid phosphatase, non-specific esterase and aminopeptidase. Fish were caught in the central part of the Adriatic Sea between 2021 and 2023. A total of 60 adult individuals were analyzed, with samples taken from six parts of the digestive tract. Histochemical analysis of 1440 slides revealed clear differences in enzyme activity between the two species. In the small-spotted catshark, cellular protein degradation was most pronounced in esophagus, posterior stomach and rectum, whereas in the smooth-hound, it was concentrated in posterior stomach and spiral intestine. Cellular digestion of lipids in the small-spotted catshark appears to occur primarily in the stomach. The results of this study provide new insights into the distribution of cellular digestive enzymes in cartilaginous fish and emphasize the importance of studying the entire digestive tract as an integrated system rather than focusing on individual parts. This study fills an important knowledge gap and contributes to a deeper understanding of digestive physiology, which in turn has implications for species conservation and biological variability.