Spectral tuning and signaling of diverse and most red sensitive visual rhodopsins that drive high colour discrimination in Mantis Shrimp eyes

Of all visual systems shaped over billions of years, stomatopod crustaceans or mantis shrimps possess arguably one of the most extraordinary eyes, with unmatched potential for broad colour detection ^1–3 . Yet how their unusual diversity of visual opsins ⁴ maps onto functional spectral sensitivities ^5,6 has remained unresolved. Here, we uncover the molecular rhodopsin-based physiological mechanisms of spectral tuning and show that seventeen opsins, mostly from the colour-sensing midband of the Neogonodactylus oerstedii eye, exhibit distinct spectral absorption ranges and couple to Gq- or Gi-proteins. Two mid-wavelength opsins (NOMs) preferentially absorb blue light, while twelve long-wavelength opsins (NOLs) absorb in the green range. In addition, three NOLs are red-sensitive beyond 600 nm, representing the most far-red-sensitive opsins functionally characterized in animals. Several opsins exhibit photoreversibility with inverse blue-red spectral shifts, revealing an unrecognised layer of photochemical flexibility in stomatopod photoreception. Combined with ommatidial carotenoid filters, our mechanistic model shows how individually tuned rhodopsins shape row-specific spectral sensitivity across the eye, promoting far-red sensitivity in tier 3P in relation to other spectral wavelengths. These specialised rhodopsin-filter combinations collectively enable robust colour vision along a broad light spectrum and across dim and bright conditions, offering new insights into the evolution of one of Nature’s most sophisticated visual systems.