Growth-regulating proteins differ between British seawater fish species, shedding light on their ecological adaptations.

Wnt proteins are a family of molecules that help control how cells grow, develop and communicate - processes that are fundamental to the development and health of all animals. Although Wnt pathways have been studied extensively in model species, very little is known about how they operate in marine fish. Understanding these pathways in fish may provide important insights into their physiology, development and ecological adaptations. In this study, we examined whether key Wnt-related proteins are present in four common British seawater fish species - mackerel (Scomber scombrus), plaice (Pleuronectes platessa), lemon sole (Microstomus kitt) and red gurnard (Chelidonichthys cuculus) - none of which have previously been investigated for Wnt expression. Using tissue sectioning and immunostaining, clear species-specific patterns were identified. S. scombrus showed expression of Wnt3, Wnt10a, Dvl1, Dvl3 and E-cadherin. P. platessa exhibited stronger expression of Wnt5a and Wnt11, with only low levels of Dvl proteins. Wnt5a was also detected in both M. kitt and C. cuculus, whereas M. kitt additionally expressed Wnt11, Dvl1 and Dvl3. Very little Dvl3 signal was observed in C. cuculus. These results provide the first evidence that Wnt-related proteins are present in these British fish species and that their expression patterns differ significantly among them. This variation may reflect species-specific developmental or ecological traits, and it lays the groundwork for future studies on the functional significance of Wnt signalling in marine fish biology.