Unusual squid eyes serve good visual capabilities

Cephalopods are successful predators with sophisticated eyes and the most complex central nervous system in the whole invertebrate taxa. Their ‘simple’ eyes possess many superficial similarities with vertebrates, providing one of the best known examples of convergence in the animal kingdom. There are fundamental eye-design differences also, such as microvillar rather than ciliary based photoreceptors, the direction of the photoreceptors face and lens shape. Here we describe another fundamental difference, a large retinal distortion or bump in the tempero-dorsal region, that apparently renders a de-focussed image of around ¼ of the frontal visual field.