Olfactory and gustatory chemical sensor systems in the African turquoise killifish: Insights from morphology.

Smell and taste are extensively studied in fish species as essential for finding food and selecting mates while avoiding toxic substances and predators. Depending on the evolutionary position and adaptation, a discrete variation in the morphology of these sense organs has been reported in numerous teleost species. Here, for the first time, we approach the phenotypic characterization of the olfactory epithelium and taste buds in the African turquoise killifish (Nothobranchius furzeri), a model organism known for its short lifespan and use in ageing research. Our observations indicate that the olfactory epithelium of N. furzeri is organized as a simple patch, lacking the complex folding into a rosette, with an average size of approximately 600 µm in length, 300 µm in width, and 70 µm in thickness. Three main cytotypes, including olfactory receptor neurons (CalbindinD28K), supporting cells (ß-tubulin IV), and basal cells (Ki67), were identified across the epithelium. Further, we determined the taste buds' distribution and quantification between anterior (skin, lips, oral cavity) and posterior (gills, pharynx, oesophagus) systems. We identified the key cytotypes by using immunohistochemical markers, i.e. CalbindinD28K, doublecortin, and neuropeptide Y (NPY) for gustatory receptor cells, glial fibrillary acidic protein (GFAP) for supporting cells, and Ki67, a marker of cellular proliferation for basal cells. Altogether, these results indicate that N. furzeri is a microsmatic species with unique taste and olfactory features and possesses a well-developed posterior taste system compared to the anterior. This study provides fundamental insights into the chemosensory biology of N. furzeri, facilitating future investigations into nutrient-sensing mechanisms and their roles in development, survival, and ageing.

Influence of Transportation on Stress Response and Cellular Oxidative Stress Markers in Juvenile Meagre (Argyrosomus regius).

In aquaculture, the transportation of live fish is a crucial but stress-inducing practice, necessitating a thorough understanding of its impact on fish welfare. This study aimed to assess the physiological stress response of meagre (Argyrosomus regius) juveniles during a 24 h commercial transport by quantifying muscle cortisol levels using a specific radioimmunoassay. Additionally, an immunohistochemical approach was used to detect and localize the cellular distribution of oxidative-stress-related biomarkers within various tissues and organs. The results demonstrated a significant increase in muscle cortisol levels following the loading procedure, remaining elevated above basal levels throughout the 24 h transport period. This effect may be attributed to either insufficient time for recovery from the loading stress or prolonged transportation-related stress. Immunostaining for all the antibodies we examined was observed in multiple tissues and organs, but we found no notable variations among the various transport phases. In conclusion, the observed stress response appears to be mainly linked to loading stress and the transport process itself, emphasizing the importance of implementing appropriate operational procedures to safeguard fish well-being during transport. Nonetheless, the unaltered distribution of oxidative stress markers between the control and transported groups suggests that the experienced stress might be within tolerable limits.