Eye: Squids contain a singular, highly developed eye that is described in peer reviewed research by Roger Villanueva and peers as having, “a single nearly spherical lens with a graded refractive index, the ability to accomodate the len and a similar capacity for eye movement, showing an example of convergent evolution” (Villanueva et al., 2017).  Additionally, an adjustable pupil works to control the amount of light that enters the eye, this pupillary constriction being one of the fastest in the animal kingdom as a whole.  Squids are also said to have the largest eye overall of the entire animal kingdom, though it serves the purpose of identification and detection above anything else.  This narrow range of tasks makes squids adept at detecting prey, as the species utilizes bioluminescent waves generated by sperm whales to detect prey, and couple this with extra-ocular light perception that makes cephalopods sensitive to polarized light.  The research article, “Cephalopods as Predators” previously mentioned highlights the advantages of polarization vision, stating, “Squid hatchlings attack planktonic prey under polarized illuminated at a 70% greater distances than under depolarized illumination” (Villanueva et al., 2017).  Additionally, the photoreceptors in the retinas of fish point away from light whereas squids and octopuses point towards the light.  This further differs from the extensively processed visual signals that fish photoreceptors receive by integrating nerve cells within the retina, which is a far more cost ineffective method than that of squid, whose photoreceptors send visual signals more directly to the brain through usage of multiple optic nerves (Hill et al., Page 11).  

Lateral Line System: Alongside compelling visual accommodations, squids also have sensory receptors within cephalopods and have the ability to detect gentle water currents and vibrations.  This occurs through ciliated primary sensory hair cells that line the arms, head, and part of the mantle, and are sensitive to movements in the water.  Research by Marta Solé and peers on the susceptibility of sound in cephalopods further examines this, detailing, “ciliated cells of this lateral line system are sensitive to local water movements and are able to perceive hydrodynamic pressure...shown to be able to detect local water movements generated by a vibrating sphere” (Solé et al., 2018).  This function is coupled with that of statocyst, which is a balance sensory receptor that allows for squid to hear, enabling the organism to hear low-frequency sounds in the water.  These functions allow cephalopods to detect particle motion, further acting as a defense-mechanism against predators and in exchange an advantageous feature in hunting down prey.