Electric Fish in Danger - Essay Example

Electric fish in danger An electric fish belongs to a special species of fish which can produce electric fields and it is also known as electrogenic.Electric fish, like any other electrogenic fish, is also electroreceptive fish and the electric fish can detect electric fields. That is to say, an electric fish is electrogenic as well as electroreceptive. Significantly, electric fish have often fascinated people to a great extent throughout history and continue to do so in the modern age. Thus, the electric fish has aroused interest and curiosity among the ancient Egyptians, Romans, Arabs and Greeks. The Egyptians have ascribed the word "thunder" to catfish, a variety of electric fish. The Greeks have referred to electric fish as "narke" which means "numbness" and the ancient Greeks were aware of the numbing power of the electric fish. There are evidences from ancient history to prove that the people of the past have effectively used the numbing properties electric fish in medical treatment. (Moller, 584) Thus, the electric fish has long enthralled human beings through its specific nature and capabilities and it continues to arouse crucial interest among the scholars of the contemporary world. The electric fish species can be found in the sea as well as in the freshwater rivers of certain regions such as South America and Africa. It is important to comprehend that the electric fish are generally divided into three categories: the strongly electric, the weakly electric and fish that can detect electricity but do not generate electricity. The most significant fishes in the first category, i.e. strongly electric fish, are electric eel, electric catfish, and electric rays, while knife fish and elephant nose are categorized as weakly electric fish. However, many fishes such as sharks, rays, paddle fish, and catfishes can detect electric fields, whereas they cannot generate electric fields, and therefore they belong to the third category of electric fish. Therefore, the most peculiar quality of an electric fish is that it can generate electric fields and the strongly electric fish can generate about six hundred volts. This paper undertakes a profound analysis of electric fish in general, its history, characteristics, electric organ and electric organ discharge, its means of communication, the various distinctions of electric fish in ecology, the different types of dangers encountered by the species, the potential pollutants affecting its existence, and how ecological factors influence the pattern and frequency ranges occupied by male and female fishes. Whereas the strongly electric fish produce several hundreds of volts of electricity, in the weakly electric fish the voltage generally does not exceed one volt. Electric fish has been the center of attraction in various scholarly discussions due to its diverse characteristics and the dangers confronting the existence of this species have offered a new area of researches. It is important to comprehend how the electric fish produce very strong electricity to shock large animals. According to the Columbia Encyclopedia, electric fish is the name for various fish which produce electricity by way of organs generally developed from modified muscle tissue. Significantly, the electric fish produce electricity at different levels and they mainly use this electric discharge to stun the prey. It is also found that the electric eel, otherwise called electrophorus electricus, which is a South American freshwater fish related to the carp, has organs along the ventral surface competent enough to produce from 450 to 600 volts of electricity. Another important electric fish, the electric ray, or torpedo, which is a freshwater electric catfish with a jellylike subcutaneous electric organ (probably of epidermal origin) that extends over the whole body, also produces several volts of electricity. There are also various species of stargazer fish which produce high volts of electricity and attract the curiosity of humans. There have been significant researches into the characteristics of various types of electric fish and important facts about how these fish produce electricity have been found. "All these fish produce electricity at will to paralyze or kill their prey, to repel their enemies, and to aid in navigation. Recent experiments have shown that when an electric eel is in motion it generates pulses of low-energy electricity which serve to detect the presence of nearby objects. Scientists believe that electric organs in fishes may function also in communication between individuals. Electric eels are classified in the phylum Chordata, subphylum Vertebrata, class Osteichthyes, order Cypriniformes, family Electrophoridae." (Electric Fish, p 15357) Therefore, the electric organs of the electric fish help this species in producing electricity to paralyze or kill their prey, to repel their enemies, to aid in navigation, and to communicate properly. In an electric fish, the electric fields are produced from an organ known as an electric organ which is located in the tail of the electric fish and this electric organ is made up of muscle and nerve cells. The electric fish have great capacity to generate high voltage shocks and can shock even larger animals with these electric fields. The capacity of the electric fish to produce electric fields has greatly attracted humanity from the ancient ages and people have often made use of this electric shock in curing human diseases. "Some electric fish can generate extremely powerful electric discharges: up to 220 volts in the electric ray; 370-550 volts in the electric eel, which also generates a much lower continual pulse; and 350-450 volts in the electric catfish. The ancient Romans used the electricity produced by electric rays to cure some health problems in people - an early form of electroshock therapy." (Aquatic Life of the World, 173) Significantly, elephant-snout fish and knife-fish generate a very feeble electric discharge, and the generally produce electric discharge less than a volt. However, this electric discharge in the electric fish is continuous or pulses intermittingly. Therefore, the electric fish has the capacity to produce strong electricity without harming itself which is used to shock its preys including large animals. However, this electricity is not used by electric fish entirely for attacking or killing the other animals, but they also use the electricity for navigation and communication in water. Thus, an electric fish is able to feel and absorb the environment and communicate through electrical signals. Significantly, the electric fish can produce electricity as well as perceive electrical impulses. The sharks, rays, catfish, common eels and electric fish etc are able to sensing and orienting to low frequency, feeble voltage gradients. "Electro-perception is widely used as a prey-seeking device. By means of feeble, steady electric fields that leak out of flatfish, sharks are able to locate these preys even when they are buried in sand. Furthermore, electric fish generate their own fields by means of electric organs consisting of highly modified muscles tissue. When prey or other objects in the water disturb the field, their presence is betrayed to the fish even when all other sensory cues are lacking. In view of this degree of sophistication, it is perhaps not surprising to find that at least some of the electric fish also use their fields to communicate with one another." (Wilson, 239-40) Therefore, the electric fish mainly use their capacity to produce strong electricity in order to attack the enemies and preys, and to make the communication effective and easy. It is mainly some of the tropical freshwater fishes and the electric fish that use electricity for navigation and communication. Significantly, the electric fish makes use of the electricity to 'feel' its environment, and they communicate to other electric fish using their electrical signals. It is essential to comprehend the various types of electric fish and the distinguishing characteristics of these varieties of species. As mentioned before, electric fishes are divided into the three main categories. The strongly electric fish include electric eel, electric catfish, and electric rays, and the weakly electric fish are knife fishes and elephant nose. The third category of electric fish can only sense electricity, while they cannot produce electricity, and the sharks, rays, skate, catfish, paddle fish, and platypus (though not a fish, they are electroreceptive) belong to this category. It is essential to note that all of these electric fishes produce electricity from an organ in the tail called an 'electric organ' which contains electrically excitable cells known as 'electrocytes'. These electrocytes receive simultaneous command signals from the brain to operate, during which the electrocytes are unevenly polarized acting as serially connected batteries. "The simultaneous firing of electrocytes results in the electric organ discharges (EODs) which are emitted in the surrounding water. In strongly electric fishes, such as the electric eel, electric catfish, and electric rays, the electric organ is huge containing numerous electrocytes. Therefore, their discharge voltage can reach as high as 600 volts. In weakly electric fishes, which use electricity for navigation and communication, the discharge voltage is small -- often less than a volt. There are two types of EODs, pulse type and wave type. All strongly electric fishes and some weakly electric fishes are pulse-type electric fishes. They discharge short electrical pulses intermittently. Some weakly electric fishes are wave type. They produce wave-like continuous A.C. electricity." (What is an electric fish) Therefore, the various types of electric fish produce electricity differently from one another and they make use of electricity for navigation as well as communication. The strongly electric fish such as electric eel, electric catfish, and electric rays can generate an excess of electricity and use it to catch food, to repel predators, and to navigate. There are two species of catfish within the family of catfish such as the small electric catfish, Malapterurus microstoma, and the electric catfish, M. electricus. "The electric catfish lives in the Nile Valley and the river systems of tropical Africa except for Lake Victoria and East Africa. It lives primarily in swamps. Although it is occasionally also found in rivers, the electric catfish stays among the reed beds at the edges of water rather than venturing into deeper waters." (Burton, 760) Significantly, the electric organ of the catfish is formed from a layer of muscle that lies like a jacket just under the skin of the main body and part of the tail. The polarity of the electric catfish runs from tail to head, while the polarity runs from head to tail in the electric eel. An electric catfish is able to discharge a shock of between 350-450 volts. In the tropical Africa, electric catfish have extensively been used as a remedy for aches and pains and the method of electrotherapy has been extensively employed in the southwestern Asia and North Africa since the 11th century. Electric eels are mostly found in South America and they are tropical American fish which can produce electricity at varying degrees. The electric eel has a cylindrical, olive-brown body which ends in a pointed tail and it can grow up to 7.5 feet long. "In common with other electric fish, the electric eel is capable of emitting a series of low-voltage discharges. The less powerful impulses form an electrical field around the fish and any object that enters the field such as a rock or another animal disrupts it. The disruption is picked up by sensory organs on the eel's skin, thereby enabling the fish to navigate and to locate prey." (Burton, 763) The electric ray is further divided into two families such as Torpenidae and Narcindae, and the largest species is the Atlantic electric ray. One of the most essential elements in the animal behavior of the electric fish in general is the fact that they communicate though the use of pulses conducted through the water. As aforementioned, there are two types of electric fish: those that produce electric pulses to stun prey or deter predators, and those that produce relatively weak electric signals used for communication. The latter category of electric fish is normally found in fresh waters in Africa as well as South America. According to Tim Halliday, "the signals are a series of pulses ranging from 10 per second in some species to 1700 per second in others. The number of pulses per second may be species specific, in which case the signal can indicate identity. The fish have sensitive electrical receptors which, in addition to their communication function, can also provide navigational information and warning of an approaching predator: they can detect minute distortions of the surrounding electrical field when another animal or object is nearby." (Halliday, 85) Therefore, one of the most essential characteristics in the behavior of an electric fish is the way in which it makes use of the electric fields in attacking, protecting, communicating and navigating. The various species of electric fish such as electric eels, elephant fish, stargazers, African electric catfish, and electric rays employ their ability to produce electric fields in the survival of the fittest. However, there are various other threats encountered by the electric fish in ecology including the pollutants of the ecosystem due to human waste, commercial pollution etc. One of the most fundamental facts about the existence of electric fish in the ecology is that they are in serious danger as the potential pollutants disrupting their environment increase at an alarming rate. Thus, the potential pollutants of the ecosystem affecting the existence of the electric fish as well as human beings include human waste, commercial pollution, and other types of water pollution. The pollution in the African rivers where the electrical fish mainly live affects the existence of these electric fish as well as human beings. Water pollution is a serious threat to the ecology in general and it affects the survival of species such as electric fish negatively. More importantly, the pollution of the water through human waste, commercial pollution, and the use of chemicals etc can affect human health. The troubling chemicals called phthalates are ever-present in modern life, and they are found in plastic bottles, cosmetics, some toys, hair conditioners, and fragrances. These chemicals can affect human health and many scientists have linked them to everything from sexual deformities in babies to obesity and diabetes. One of the essential problems with the phthalates is that they suppress male hormones and sometimes mimic female hormones. These chemicals can be dangerous to the various species of fish including electric fish. According to Nicholas D Christof, "chemicals called endocrine disruptors are believed to explain the proliferation of "intersex fish" - male fish that produce eggs - as well as sexual deformities in animals and humans. Phthalates (pronounced THAL-ates) are among the most common endocrine disruptors, and among the most difficult to avoid. They're even in tap water, and levels soar in certain plastic water bottles." (Christof) Therefore, chemicals or endocrine disruptors such as Phthalates make life difficult to human beings as well as species such as the electric fish. Significantly, one of the major threats to the survival of the electric fish is raised from various types of pollutants, due to human waste, commercial pollution, chemicals etc. endocrine disruptors or environmental hormones make life difficult to these species including electric fish and human beings. Water pollution in different forms affects the ecosystem in general and the dangers encountered by electric fish are the best example of the bad effects of human interference of the ecosystem. "Various types of endocrine disruptors or environmental hormones flow from their sources down into harbours through rivers and other watercourses, and are accumulated in sediment on the sea bottom. Tributyltin, which has been used as paint for ship bottoms, is considered one of the endocrine disruptors." (Yosokawa) Therefore, endocrine disruptors or environmental hormones affect the living environment of the electric fish and they are in danger. One of the most effective solutions to the issues of human waste etc which negatively affect the ecology and the survival of species such as electric fish is the careful and vigilant approach of the nature by humanity. Managing our natural resources must be given high priority and effective measures need to be adopted for the preservation of species such as the electric fish. Works Cited Aquatic Life of the World. New York: Marshall Cavendish Corporation. 2000. P 173. Burton, Robert. International Wildlife Encyclopedia. New York: Marshall Cavendish. 2002. P 760. Christof, Nicholas D. "Chemicals and Our Health." 2009. 11 August, 2009. . "Electric Fish." The Columbia Encyclopedia. 6th Ed. New York: Columbia University Press. 2007. P 15357. Halliday, Tim. Animal Behavior. University of Oklahoma Press. 1994. P 85. Moller, Peter. "Electric fishes - History and behavior." Fish and Fisheries Series. London: Chapman and Hall. Vol. 17. 1995. P 584. "What is an electric fish" 11 August, 2009. . Wilson, Edward O. Sociobiology. Harvard: Harvard University Press. 2000. P 239-40. Yosokawa, Y et al. "The nationwide investigation of endocrine disruptors in sediment of harbors." Mar Pollut Bull. Vol. 47. Iss. 1-6. 2003. P 132-8. 11 August, 2009. . Read More