Gene expression intensities of rhodopsin and retinochrome in the retina of three Sepioteuthis spp. and the relationship with their habitats

Abstract

　The maximum absorption wavelength (λ_max) of the photosensitive pigment retinochrome present in the retina of squids is approximately 10 nm longer than that of rhodopsin, and it is known to be abundant in deep-sea species. When comparing the λ_max difference between the two pigments among three species of Sepioteuthis spp., the difference in S. sp. 2, which is common in Honshu, was 17 nm, and less than 2 nm for southern species of S. sp. 1 and S. sp. 3. Retinochrome gene expression intensity was higher in S. sp. 2, which is common in inland bays, than in S. sp. 1, which occurs in deep waters. The habitat of S. sp. 2 has greater fluctuations in turbidity than that of the other two species, and it is presumed that S. sp. 2 adapts its visibility to the complex light environment by actively utilizing two photopigments with different λ_max.