What organs or structures are responsible for helping a crab hear?
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Crabs have innervated sensilla or setae that cover their body and appendages; some of these are mechanoreceptors that can sense touch and currents, including vibrations (sound waves). \nAt least for shrimps, their statocyst (equilibrium organ) has been demonstrated to be also a hearing organ (see the scientific paper at the link).\nThe sea is filled with sound, as sound vibrations travel exceptionally well in the aquatic medium. In addition, several crustaceans produce sounds themselves. Therefore it's only logical that they have evolved sound receptors of different types.
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The Praying Mantis.\n\nEars occur in 60% of mantids, and are found on the underside of the mesothorax.  The mantis is an auditory Cyclops, and having only one ear is a feature unique to the mantis, not seen anywhere else in the animal kingdom.  The ear is a deep 1 mm slit that has cuticle knobs at either end and two eardrums inside.  It is located in the ventral midline between the metathoracic legs.  Interneurons in the metathoracic ganglia mediates hearing.  The ear is tuned to ultrasonic frequencies of 25-60 kHz, with thresholds of 55 to 60 decibels.  This is the range of bat's echolocation, supporting evidence that mantids, like lacewings, moths, and crickets, use hearing as a defense against predators
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Ghost crabs live in burrows along the sandy beaches of the Eastern United States. The crabs can reach relatively large sizes of over 50 mm carapace width. They are omnivorous and will eat other crabs, clams, insects, vegetation, and detritus. Feeding activity takes place at night, while burrowing occurs during the day. Burrows show zonation with young crabs found closer to shore, near water. Older crabs tend to burrow farther from water. The large eyes of the crab are sensitive to changes in light intensity. The crab can produce 3 sounds: a rapping of the claw on the substrate, a rasping stridulation of the legs, and a bubbling sound presumably produced from the gill chamber. Combat between males is highly ritualized and rarely ends with contact.\n\n  \n  http://www.vims.edu/~jeff/ghost.htm
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"Some muscles attached to the external ear in humans seem vestigial in terms of evolution.  Some of us can wiggle our ears, some of us cannot.  In lower mammals, dogs for instance, these muscles allow exquisite control of the external ear for purposes of moving them to better able to detect where sounds originate.  In some aquatic animals, the little tab of skin in front of the ear canal, called the tragus, can be operated to act as a valve to open and close the ear canal.\n\nHowever, the earlobe itself has no known biological function."
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This is going way back for me, but I thought that most crustaceans you had to actually dissect them before you could tell.  Sorry, I might be thinking of another class of animals.  I remember learning the answer to your question way back in junior high.
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they have horns. Look for small antennae at the back of their head too thats a sure sign that they are good freinds. Just keep those bots away from water
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This depends on the animal, a number of different types of animals can hear much better than we can.  However there are some animals like turtles and snakes that can only hear very low frequency sounds.  In spite of what many people think neither turtles or snakes are actually deaf.  Some of this has to do with the anatomy of the ear.  Mammals have 3 ear bones; the stapes, the malleus and the incus.  While fish only have a stapes.  This was the result of evolution so that animals could develop better hearing for a number of different reasons such as 1) better hearing required on land as sound travels better through water than land and 2) the development of a means of communication between one another.  These are the only 2 i can think of off hand but there is a lot of interesting information about the evolution hearing in animals out there.
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Its called the stapes (stirrup) in the ear
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Fishes have well-developed nervous systems that organize around a central brain, that is divided into different parts. The most anterior, or front, end of the brain are the olfactory bulbs, which are involved in the fish's sense of smell. Unlike most vertebrates, the cerebrum of the fish is primarily processes the sense of smell rather than being responsible for all voluntary actions. The optic lobes process information from the eyes. The cerebellum coordinates body movements while the medulla oblongata controls the functions of internal organs. Most fishes possess highly developed sense organs. Nearly all daylight fish have well-developed eyes that have color vision that is at least good as a human's. Many fish also have specialized cells known as chemoreceptors that are responsible for extraordinary senses of taste and smell. Although they have ears in their heads, many fish may not hear sounds very well. However, most fishes have sensitive receptors that form the lateral line system. The lateral line system allows for many fish to detect gentle currents and vibrations, as well as to sense the motion of other nearby fish and prey. Some fishes, such as catfish and sharks, have organs that detect low levels electric current. Other fishes, like the electric eel, can produce their own electricity.
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tell him you have crabs
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Crabs run or move sideways because that is the way their legs bend. Crabs do not have ball-and-socket joints; many crabs have joints in their legs moving in a restricted number of planes so that they can only move sideways. Many crabs like the "Shore Crab" need to scamper sideways to avoid the legs getting tangled up with each other. \n\nMuscles work in pairs. A muscle can only retract, or pull; to lengthen again it must relax and be pulled back by another 'antagonistic' muscle. The muscle blocks in crabs are attached to the inner surface of the exoskeleton, including the ten tubular legs, including the legs with claws, or chelae, as well as other appendages.\nAslo,For animals, their body lengths are normally larger than the widths. For locomotion, animals usually move along the long axis of their bodies. As crabs run sideways, they are moving along the long axis of their bodies.\n\nCrabs are scavengers; they do not need to move forward in pursuit of preys like predators do.
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The mandible (jaw).\n\nUnless you want to consider the 3 small bones in each inner ear (hammer, anvil and stirrup).
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Crabs are body lice that manifest usually in the groin because it's warm and moist. They attach themselves to pubic hair and also attach their eggs to pubic hair. When they are hungry they feed on blood. They cause itching when they're on the move, and as a result of feeding. They are tiny (about or smaller the size of a pin head) and are almost transparent. Their eggs are also almost transparent.
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Sloths sometimes let out a cry or hissing sound
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D;hearing,\nbodily function:bowel movement
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I'm partial to crabs. They are misunderstood. Each one has their own personality and temperament. Some even do tricks. It's a shame we execute them so quickly upon discovery.
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I assume you know that the ear is composed of the outer ear, the middle ear and the inner ear. Here’s the gist of it:\n\nSound Source  Sound Medium (Air)  Ear (Auditory Canal)  Eardrum Vibrates [Acoustic Energy]  Ossicles Bones Vibrate [Mechanical Energy]  Fluids in the Cochlea Vibrate [Hydrolic Energy]  Auditory Nerve (8th Cranial Nerve) [Nerve Impulses]   Brain (the vestibular centers (nuclei) in the Brainstem)  1) Ipsilateral Cochlear Nucleus  2) Superior Olivary Nucleus  3) Inferior Colliculus Medial Geniculate Nucleus (Sensory Thalamus)  Auditory Cortex (Temporal Lobe).\n\nIn relation to the ‘loud sound’, I assume you mean ASR: Acoustic Startle Reflex:\n\nLoud sounds causes the Stapedius Muscle (which is innervated by the 7th cranial nerve (facial nerve)) to tighten the Stapes (ossicles) in an attempt to ATTENUATE the sound and protect the eardrum. The Acoustic Reflex Arc ascends from the outer ear to the brainstem and then descends via the facial nerves on both sides of the head to innervate the stapedial muscles in both middle ears.\n\nThe ASR Circuit is as follows: Cochlear Nucleus  Ventral Lateral Pons [Brainstem]  Reticular Formation (pons) [Brainstem]  Spinal Motor Neurons (whole body startle).