John McCluskey escaped from an Arizona prison in the summer of 2010, killed an elderly couple, burned their bodies and stole their truck. Eventually, he was recaptured, tried and found guilty of murder. Sentencing became difficult because the jury had been provided with copies of McCluskey’s PET scans that showed unusual brain activity (ICD-10-CM code R93.0). Ten areas of his brain were oddly inactive, while seventeen brain areas were working overtime. The defense team stated that John was basically a victim of bad biology and should not be unduly punished for his faulty brain. As a result, the jury couldn’t decide if McCluskey should receive the death penalty, so he was sentenced to life without parole. His intracranial function had saved him from walking the green mile, because the jury believed his brain made him do it.
Tunicates, commonly called sea squirts, are a group of marine animals that spend the majority of their lives attached to rocks, shells, docks or the underside of boats. A tunicate is built like a barrel-shaped colored blob of jelly and the name “tunicate” comes from the firm, flexible body covering, called a tunic. This tunic contains cellulose, a glucose polysaccharide not normally found in animals. Sea squirts are found in great numbers throughout all the seas of the world, from the Polar Regions to the tropics. Free-swimming tunicates are found floating and swimming in open water as planktonic drifters.
Tunicates are part of the phylum Urochordata, closely related to the phylum Chordata that includes all vertebrates. Adult sea squirts are filter feeders, with two major openings through which water enters and exits. The tunicate larva, or tadpole, has a nerve cord down its back that is similar to the nerve cord found inside the spine of all vertebrates. Within the tail (which comprises about two-thirds of the sea squirt during the larval phase), the cerebral vesicle is equivalent to a brain, and sensory organs include an eyespot to detect light and an otolith which helps the tadpole orient to gravity.
Tunicate tadpoles mature quickly, requiring only a few hours to reach adulthood. The tadpoles have no mouths and do not feed at this stage; their only job is to find a suitable place to live out their adult lives. Once they find the rock, wharf piling, shell, boat, off-shore oil rig or other solid structure to call home, they secrete a sticky substance that allows them to attach head first to their chosen spot. As the metamorphosis to an adult takes place, there are considerable changes in size and proportion of their body parts. During this process the mouth forms and is directed away from the point of attachment that has become the posterior end of the animal. The larva reabsorbs the tail, cerebral vesicle and other sensory organs within a single day, and the materials in the tail are recycled to build new structures needed for adult life. This repurposing of unnecessary internal organs essentially means that the tunicate eats its own brain during the transition process (ICD-10-CM code G93.82, brain death).
In a related event, pop culture zombies (not the zombies of Haitian and West African folklore) reportedly terrorize the non-zombie population and feed on the brains of the living. Does that mean that sea squirts become zombies when they consume their own cranial tissue? Definitely food for thought.