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Pain in crustaceans. Close up of the head of a live lobster. There is a scientific debate which questions whether crustaceans experience pain. It is a complex mental state, with a distinct perceptual quality but also associated with suffering, which is an emotional state.
Pain in invertebrates is a contentious issue. Although there are numerous definitions of pain, almost all involve two key components. First, nociception is required. This is the ability to detect noxious stimuli which evokes a reflex response that moves the entire animal, or the affected part of its body, away from the source of the stimulus.
A typical human cutaneous nerve contains 83% C type trauma receptors (the type responsible for transmitting signals described by humans as excruciating pain); the same nerves in humans with congenital insensitivity to pain have only 24-28% C type receptors. [23] The rainbow trout has about 5% C type fibres, while sharks and rays have 0%. [24]
Sensory systems in fish. Most fish possess highly developed sense organs. Nearly all daylight fish have colour vision that is at least as good as a human's (see vision in fish). Many fish also have chemoreceptors that are responsible for extraordinary senses of taste and smell. Although they have ears, many fish may not hear very well.
Snow crabs, a cold-water Arctic species, thrive overwhelmingly in areas where water temperatures are below 2 degrees Celsius, though they can physically function in waters up to 12 degrees Celsius.
Crab (Pachygrapsus marmoratus) on Istrian coast, Adriatic Sea. Crabs attract a mate through chemical (pheromones), visual, acoustic, or vibratory means. Pheromones are used by most fully aquatic crabs, while terrestrial and semiterrestrial crabs often use visual signals, such as fiddler crab males waving their large claws to attract females.
Red crabs have only been commercially fished for about 30 years, so little is known about their biology and reproduction. The National Marine Fisheries Service has deemed them a data-poor stock.
Decapod anatomy. The decapod (crustaceans such as a crab, lobster, shrimp or prawn) is made up of 20 body segments grouped into two main body parts: the cephalothorax and the pleon (abdomen). [1][2] Each segment may possess one pair of appendages, although in various groups these may be reduced or missing. They are, from head to tail: