Yamato Tachibana (Tachibana; Citrus tachibana) is an endemic fruit and represents one of the oldest citrus species in Japan; it is grown in the Mie Prefecture. It has been attracting attention for its cultural heritage and unique scent. To evaluate biological activities of Tachibana, we fed several parts of the Tachibana fruit (whole fruit, pulp [albedo and segment wall], and flavedo) to adult zebrafish and found that Tachibana increased body weight and plasma triglycerides besides increasing overall food intake. We then created a simple fluorescence-based feeding assay using dried rotifer sheets and larval zebrafish (6 days postfertilization) to screen the various extracts of Tachibana parts. We found that water extracts of Tachibana pulp increased feeding volume in zebrafish. Although citrus species are believed to prevent obesity and obesity-associated diseases in general, our findings showed that water extracts of Tachibana increase food intake in zebrafish and lead to an increase in body weight. We suggest that Tachibana might reverse appetite loss in lean populations and may prove beneficial in aiding fish cultivation.

Nanomaterials of various shapes and dimensions are widely used in the medical, chemical, and electronic industries. Multiple studies have reported the ecotoxicological effects of nanaoparticles when released in aquatic and terrestrial ecosystems; however, information on the toxicity of silver nanowires (AgNWs) to freshwater organisms and their transfer through the food webs is limited. In the present study, we aimed to evaluate the toxicity of 10- and 20-μm-long AgNWs to the alga Chlamydomonas reinhardtii, the water flea Daphnia magna, and the zebrafish and study their movement through this three-species food chain using a variety of qualitative and quantitative methods as well as optical techniques. We found that AgNWs directly inhibited the growth of algae and destroyed the digestive organs of water fleas. The results showed that longer AgNWs (20μm) were more toxic than shorter ones (10μm) to both algae and water fleas, but shorter AgNWs were accumulated more than longer ones in the body of the fish. Overall, this study suggests that AgNWs are transferred through food chains, and that they affect organisms at higher trophic levels, potentially including humans. Therefore, further studies that take into account environmental factors, food web complexity, and differences between nanomaterials are required to gain better understanding of the impact of nanomaterials on natural communities and human health.