Ontogenetic changes in spectral sensitivity and retinal topography in the retina of the yellowtail kingfish (Seriola lalandi): Implications for the global Seriola aquaculture industry

The visual environment of several aquaculture species has been shown to be crucial for increased survival and growth. However, very little is known about the visual system of the increasingly popular Seriola genus and its developmental changes. We investigated the ontogenetic changes in colour vision and spatial resolution in the yellowtail kingfish, S. lalandi and discuss them in relation to past behavioural feeding experiments. Microspectrophotometry was used to measure the spectral sensitivities of photoreceptor visual pigments in larvae and sub-adults. The yellowtail kingfish larva has a broad spectral range including ultraviolet-sensitive (UVS) single cones, middle-wavelength-sensitive (MWS) single cones, MWS twin cones and long-wavelength-sensitive (LWS) twin cones. The overall spectral range narrows during development through the loss of the LWS twin cones and a general short-wavelength shift in the spectral sensitivities of the other photoreceptor types. As a sub-adult the yellowtail kingfish also gains a short-wave-sensitive (SWS) single cone. This suggests that different lighting conditions will be optimal for larvae and sub-adults. No changes are observed in retinal ganglion cell (RGC) distribution between juveniles and sub-adults. A temporal concentric increase in RGC density and a weak horizontal band of medium RGC density (30% of the peak density) are present at both stages. This suggests that no changes in the feeding behaviour will occur throughout growth although the sub-adult possesses 1.6 times higher spatial resolution which would increase feeding accuracy at higher pellet densities. Research into the spectral properties of feed types combined with the data obtained here will allow for better contrast between prey and background by optimising lighting conditions.