Octopamine Effects on Crustaceans

There are over 50,000 invertebrate crustacean species in the world. They are consumed by many predators and exhibit a variety of protective behaviors. Many types of neurohormones, such as octopamine, are found in crustaceans to facilitate these particular behaviors. Octopamine is similar to the effect of the neurotransmitter norepinephrine in vertebrates. It is associated with submissive, feeding and sexual behaviors.

  1. Crustaceans Defined

    • Invertebrate crustaceans occur both aquatically and terrestrially. An invertebrate has no backbone or internal skeleton. Crustaceans have a hard exoskeleton shell, a segmented body, a primitive nerve cord and a nerve bundle near the antennae. Years ago, scientists believed that crustaceans did not feel pain or stress. With the discovery of neurohormones, neurotransmitters and neuromodulators, scientists have found significant behavioral changes related to crustacean nervous system stimulation.

    Effect on Posture

    • Many crustaceans use posturing as a form of communication. Since octopamine is similar to norepinephrine in counteracting aggression, increasing octopamine causes submissive posturing in crustaceans. According to the 1997 issue of the "Journal for Comparative Physiology," squat lobsters given octopamine injections sat flat on their tails, with their four legs and claws in a forward position. This stance placed the lobster's body lower compared with other lobsters and exhibited a submissive posture.

    Effect on Tail Flipping

    • Crayfish, lobsters and shrimp possess a long abdomen used for propelling them through the water by tail flipping. These crustaceans usually use this when they are startled to escape dangerous situations. The tail-flipping behavior is mediated by a network of nerves, and high doses of the neurotransmitter octopamine will elicit tail-flipping and scuttling responses without provocation. Therefore, octopamine is vital to the crustacean's survival.

    Effects on Shaking

    • Certain doses of octopamine on lobsters made their legs, claws and abdomens shake. As the octopamine dosage increases, so does the shaking. The shaking may be intermittent or constant and lasts several minutes. High doses of octopamine cause lobsters to become completely immobilized by the violent shaking. The mechanism for the shaking is unknown, but the exhibited actions differ among crustaceans.

    Octopamine Location

    • Octopamine is present in various neurological tissues of crustaceans, and its effect may depend on its location. Octopamine has been detected extensively in eyestalks, brain, circumesophageal connectives and the ventral nerve cord of crustaceans. Increased octopamine affects the gastric nervous system in a crab by increasing its stomach contractions. Any place within a crustacean's body that contains nerves can be affected by octopamine.