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Lateral Lines by Bill Harvey
Well, I am not sure I remember it all, but here goes with that which I DO remember. The lateral line system is a set of sense organs which are restricted to the fishes and (I think) some aquatic stages of amphibians. In some ways, it shares nerve pathways with the auditory system of the fishes inner ear, but it is a distinct sensory system. Lateral lines are actually canals with pores in either skin or scales around the head and body of the bony fishes, although some systems with the Elasmobranchs (sharks) also would be classified within the general definition of lateral line systems. In the Chondricthyes, the ampullae of Lorenzini are examples. These are very powerful means of assessing prey species in the sharks, not only do they pick up sound and other sources of vibration, they sense (I swear this is true) mild electrical fields. In freshwater, it seems I recall that catfish species (Ictaurus, specifically) can detect weak electrical fields. (I digress here for a second. The red drum has a very distinct lateral line system and structures similar to ampullae of Lorenzini--at least in how they look--around the head. I have seen reds come up under a popper and "nose" it then swim away. Actually lifting it out of the water. I am convinced they are either seeking or repelled by weak electrical fields around that fly and its associated hook. Any metallic object dragged through saltwater will generate some level of static electricity. As Casey Stengel said, "You can look it up.") The lateral line is innervated by the cranial nerves and have a close association with the with auditory nerves. This is SO COOL, there are centers in the medulla oblongata (the fishes so called dinosaur brain) which are divided into to groups, one for the head of the fish and one for the area along the body. The secondary connections relay this information to the fishes eyes and brain. OK, how do they work? The basic receptor is called a neuromast, an area of sensory tissue that has a sort of hair in it. The sensory cells of the neuromast have hair-like structures called cilia. Some of these hairs point to the head of the fish, some toward the tail, but are all lined up along the general longitudinal axis of the fish. OK, now, as vibrations or other stimuli reach these hairs, some bending toward the head, some toward the tail, it is not hard to see how when stimulated, these hairs immediately relay information to the fish about the general direction of the stimulus! The lateral line responds to a lot of different stimuli like irregular pressure waves and LOW-Frequency vibrations in the neighborhood of 50-100 cps. The lateral line, then alerts the fish to localized disturbances, caused by small currents, mechanical vibrations below 100 cps or of displacement of the surrounding water. They system sort of acts like an ability to touch at long distance. It allows the fish to sense moving objects such as predators or prey or to sense fixed objects that reflect water movements caused by the fishes own swimming. Ever wonder why reds will spook when they hear you wading or when a pressure wave off your shins reaches them. Lateral line in action. Or why they are drawn to rattles or to popping bugs or flies? Lateral line. Very powerful sensing organ. Thanks to John McEachron (Ichthyology), Ira Greenbaum (comparative anatomy) and Drew Harvey (my dad) Bill

Lateral Lines by Bill Harvey

Well, I am not sure I remember it all, but here goes with that which I DO remember.

The lateral line system is a set of sense organs which are restricted to the fishes and (I think) some aquatic stages of amphibians. In some ways, it shares nerve pathways with the auditory system of the fishes inner ear, but it is a distinct sensory system.

Lateral lines are actually canals with pores in either skin or scales around the head and body of the bony fishes, although some systems with the Elasmobranchs (sharks) also would be classified within the general definition of lateral line systems. In the Chondricthyes, the ampullae of Lorenzini are examples. These are very powerful means of assessing prey species in the sharks, not only do they pick up sound and other sources of vibration, they sense (I swear this is true) mild electrical fields. In freshwater, it seems I recall that catfish species (Ictaurus, specifically) can detect weak electrical fields. (I digress here for a second. The red drum has a very distinct lateral line system and structures similar to ampullae of Lorenzini--at least in how they look--around the head. I have seen reds come up under a popper and "nose" it then swim away. Actually lifting it out of the water. I am convinced they are either seeking or repelled by weak electrical fields around that fly and its associated hook. Any metallic object dragged through saltwater will generate some level of static electricity. As Casey Stengel said, "You can look it up.")

The lateral line is innervated by the cranial nerves and have a close association with the with auditory nerves. This is SO COOL, there are centers in the medulla oblongata (the fishes so called dinosaur brain) which are divided into to groups, one for the head of the fish and one for the area along the body. The secondary connections relay this information to the fishes eyes and brain.

OK, how do they work? The basic receptor is called a neuromast, an area of sensory tissue that has a sort of hair in it. The sensory cells of the neuromast have hair-like structures called cilia. Some of these hairs point to the head of the fish, some toward the tail, but are all lined up along the general longitudinal axis of the fish. OK, now, as vibrations or other stimuli reach these hairs, some bending toward the head, some toward the tail, it is not hard to see how when stimulated, these hairs immediately relay information to the fish about the general direction of the stimulus!

The lateral line responds to a lot of different stimuli like irregular pressure waves and LOW-Frequency vibrations in the neighborhood of 50-100 cps. The lateral line, then alerts the fish to localized disturbances, caused by small currents, mechanical vibrations below 100 cps or of displacement of the surrounding water. They system sort of acts like an ability to touch at long distance. It allows the fish to sense moving objects such as predators or prey or to sense fixed objects that reflect water movements caused by the fishes own swimming.

Ever wonder why reds will spook when they hear you wading or when a pressure wave off your shins reaches them. Lateral line in action. Or why they are drawn to rattles or to popping bugs or flies? Lateral line.

Very powerful sensing organ.

Thanks to John McEachron (Ichthyology), Ira Greenbaum (comparative anatomy) and Drew Harvey (my dad)

Bill

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