Tell us about the arowanaâaka the dragon fishâand why it has become so valuable. The Asian arowana is the worldâs most expensive aquarium fish. It is a tropical freshwater fish from Southeast Asia that grows three feet long in the wild. Thatâs roughly the size of a snowshoe. [Laughs.] It is a fierce predator dating back to the age of the dinosaurs.
A personality disorder is an enduring pattern of inner experience and behavior that deviates markedly from the expectations of the individual's culture, is pervasive and inflexible, has an onset in adolescence or early adulthood, is stable over time and leads to distress or impairment.
Parkinsonâs disease (PD) is a degenerative, progressive disorder that affects nerve cells in deep parts of the brain called the basal ganglia and the substantia nigra.o understand Parkinson's, it is helpful to understand how the nervous system works and how PD affects normal functions (see Anatomy of the Brain). Nerve cells, or neurons, are the basic building blocks of the nervous system. The neuron is responsible for sending and receiving nerve impulses or messages.