<P> While a starfish lacks a centralized brain, it has a complex nervous system with a nerve ring around the mouth and a radial nerve running along the ambulacral region of each arm parallel to the radial canal . The peripheral nerve system consists of two nerve nets: a sensory system in the epidermis and a motor system in the lining of the coelomic cavity . Neurons passing through the dermis connect the two . The ring nerves and radial nerves have sensory and motor components and coordinate the starfish's balance and directional systems . The sensory component receives input from the sensory organs while the motor nerves control the tube feet and musculature . The starfish does not have the capacity to plan its actions . If one arm detects an attractive odour, it becomes dominant and temporarily over-rides the other arms to initiate movement towards the prey . The mechanism for this is not fully understood . </P> <P> The body cavity contains the circulatory or haemal system . The vessels form three rings: one around the mouth (the hyponeural haemal ring), another around the digestive system (the gastric ring) and the third near the aboral surface (the genital ring). The heart beats about six times a minute and is at the apex of a vertical channel (the axial vessel) that connects the three rings . At the base of each arm are paired gonads; a lateral vessel extends from the genital ring past the gonads to the tip of the arm . This vessel has a blind end and there is no continuous circulation of the fluid within it . This liquid does not contain a pigment and has little or no respiratory function but is probably used to transport nutrients around the body . </P> <P> Starfish produce a large number of secondary metabolites in the form of lipids, including steroidal derivatives of cholesterol, and fatty acid amides of sphingosine . The steroids are mostly saponins, known as asterosaponins, and their sulphated derivatives . They vary between species and are typically formed from up to six sugar molecules (usually glucose and galactose) connected by up to three glycosidic chains . Long - chain fatty acid amides of sphingosine occur frequently and some of them have known pharmacological activity . Various ceramides are also known from starfish and a small number of alkaloids have also been identified . The functions of these chemicals in the starfish have not been fully investigated but most have roles in defence and communication . Some are feeding deterrents used by the starfish to discourage predation . Others are antifoulants and supplement the pedicellariae to prevent other organisms from settling on the starfish's aboral surface . Some are alarm pheromones and escape - eliciting chemicals, the release of which trigger responses in conspecific starfish but often produce escape responses in potential prey . Research into the efficacy of these compounds for possible pharmacological or industrial use occurs worldwide . </P> <P> Most species of starfish are gonochorous, there being separate male and female individuals . These are usually not distinguishable externally as the gonads cannot be seen, but their sex is apparent when they spawn . Some species are simultaneous hermaphrodites, producing eggs and sperm at the same time and in a few of these, the same gonad, called an ovotestis, produces both eggs and sperm . Other starfish are sequential hermaphrodites . Protandrous individuals of species like Asterina gibbosa start life as males before changing sex into females as they grow older . In some species such as Nepanthia belcheri, a large female can split in half and the resulting offspring are males . When these grow large enough they change back into females . </P>

What type of symmetry did your starfish have