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·. ' ELECTRIC FISHES \ \ I , J ., \ I 'I November 7, 1968 " • - CONTE~TS .,• ' .. . . . . . . . . . . . . . . . .. ................................ . ... I. INTRODUCTION 1 II. ELECTRIC ORGANS ••••••••••••••••••••••••• • ••••••••••••••••••••••••••• 2 ~Iorphology . . . . . . . . . . .. . . . . . . .• • • . • . . . . . . . . . • • . . . . . . • . . . . . . . . . . • . . . • . 2 ............................................ Electrophysiology 7 .. .................. . III. NAVIGATION AND .DETECTION l-HTH ELECTRIC FIELDS 11 .. ....................................................... . IV. REFERENCES 14 .. . • .. ., I. INTRODUCTION > I ~· There are seven families of marine and fish capable of fresh~water deliver~ ing appreciable voltages outside their bodies. For example, the giant electric ray (Torpedo nobiliana) can electrocute a large fish with its pulses of 50 amperes at 50 to 60 volts. Though much smaller, the African catfish (Malaoterurus) pro duces as much as 350 volts, and the electric eel (Electrophorous) of the Amazon and other South American rivers puts out more than 500 volts. In contrast, there are weakly electric· ·fishes· which generate from a few tenths to several volts, • but even these species exceed the highest output of other animals which produce minute electrical currents in their nervous, muscular, and glandular tissue. " . There now see. ms to be no doubt about the· survival value of the peculiar capability of the electric fishes. For the powerfully electric species it ser ves obyious offensive and defensive functions, and recent work has shown that ·in the weakly electric ones it serves as part of a sensory guidance system for navigation in murkey waters and for the detection of predators and prey. The advantages, in fact, are such that natural selection brought about the develop ment of electric organs quite independently in almost every one of the families" (Grundfest, 1960a, pp. 115-116). In several cases, different physiological so lutions were developed for the generation of electrical energy and the shaping and timing of the electric pulses. "Animal electricity" was first studied in electric fishes, and throughout the 19th century these animals were the center of resear.ch on electrophysiology. As This is a digital image that presents information about declassified government documents from "The Black Vault." On the left side of the image, there is a graphic of a vault door, with a complex locking mechanism and a luminous blue glow emanating from it. The right side of the image contains text explaining that the document was obtained from The Black Vault, an online database of declassified government documents, specifically mentioning the MKULTRA/Mind Control Collection. It also provides a URL for accessing the collection. There are no photographs of people, locations, equipment, or subjects, nor are there any handwritten annotations, signatures, official stamps, forms, diagrams, tables, redacted content, or visual evidence of experimental procedures on this page. The document appears to be a title page or a preliminary page from a report titled "ELECTRIC FISHES." It is dated "November 7, 1968." In the bottom right corner, there is a handwrittencircled number "250". The page is largely blank, with scattered small dark marks and a faint vertical line appearing in the upper right quadrant, possibly a printing artifact or a stray mark. There are no photographs, diagrams, forms, or stamps visible. 1960a, pp. 115-116). In several cases, different physiological so lutions were developed for the generation of electrical energy and the shaping and timing of the electric pulses. "Animal electricity" was first studied in electric fishes, and throughout the 19th century these animals were the center of resear.ch on electrophysiology. As far back as 1791 Galvani suggested that there was a kinship between the elec tricity. of "torpedo and cognate animals" and the "animal electricity" that he be lieved he had observed in muscles and nerves. A dispute arose between Galvani and Volta wherein the latter thought that Galvani had demonstrated "metallic" electricity by the contact of two dissimilar metallic surfaces rather than ani mal electricity. This was correct in that Galvani's frog nerve-muscle prepara tions were merely more sensitive detectors of electricity than any instruments available at that time. But "Volta was wrong in denying the existance of ani mal electricity. In trying to prove his contention that the electric fish con _tained some sort of generator Volta discovered the electrochemical battery, or 'galvanic' cell. The 'voltaic pile' of cells in series he called 'an artifi·cial electric· organ' which he thought 'victoriously demonstrated' his argument" (Grundfest, 1960a, p. 117). At the present time, work·on electric fish offers some potentially very useful leads to the solution of the problems of synaptic transmission such as the induction by the.nerve impulse of the chemical mechanism that underlies the .. relay of the impulse from one nerve to the next and from the nerve cell to muscle or gland tissue • ·. - II. ELECTRIC ORG&~S Morphology Electric organs are derived from muscle and consist of an array of cells called electroplaques. These component cells may be stacked in columns like a roll o.f coins along each side of the body, running longitudinally and parallel with the spinal column. The eel is an example of this type and has some 6,000 to 7,000 electroplaques in each column, with 70 columns in the organs on each side of its body. ·In the adult eel they make up about 40 percent of the bulk .of the body. In contrast, the columns in the electric ray are arranged verti cally, i.e. at right angles to the spine, forming a large ·compact electric organ in each of the animal's wings. A third pattern is found in the African catfish, in which the organ is in t!:te form of This image displays a table of contents from a document. The content is structured with Roman numerals and sub-sections, each with a corresponding page number. The document appears to be from a report or technical paper, covering topics such as "Introduction," "Electric Organs," "Morphology," "Electrophysiology," "Navigation and Detection with Electric Fields," and "References." There are no photographs, handwritten annotations, stamps, forms, diagrams, tables, redactions, or visual evidence of experimental procedures on this page; it is purely a textual outline. body. In contrast, the columns in the electric ray are arranged verti cally, i.e. at right angles to the spine, forming a large ·compact electric organ in each of the animal's wings. A third pattern is found in the African catfish, in which the organ is in t!:te form of a mantle of tissue just the skin, . belo~v surrounding the entire body from gills to the tail. The bilateral electric or gans of several species are in Figure 1. sho~vn Each electroplaque is a thin wafer-like cell whose two surfaces differ markedly. In most species, one surface· is innervated directly by a dense net work of nerve terminals or indirectly through one or several stalks lvhich emerge from one of the electroplaque surfaces (Figures 2 and 3). But in almost all cases only one surface of the cells is innervated. The opposite side has a number of deep folds and convolutions to increase its total area. All of the electroplaques in one species are oriented in the same way. In addition to the main organ, an accessory electric organ is present in the electric ray. The electroplaques of this organ have a different orientation, i.e.,_ they are in nervated on their dorsal rather than their ventral surfaces. The surface of the electroplaques innervated and other aspects of their structure in a number of electric fish are summarized in Table 1. ·. - ~~~;,:::,~::~ .. · · , · .. . .. ..., .. ~~etrfB~~~J •'•'I I_..,.,. .. ,, , ,., . ··,-_:.r-J.-• :11 -~"tt••:- . a ...~ . . ,•. ,, · .;# · . . . .. . . · . . . · . - .- · 7 · , f • " • .. · .; · ;J · ., " :• r• ' · , ' • ' • i ; / J' 3 : ' · - : ' ~ , ' , ' , i t 1 , l ' , " /. , t , ' ~ • ' . - . ,. . ., , . " .,. ... . ._ ___ • __ "" 4 "" - - ' ; 1 . J " . i: J ~ · # ,. ~ ~, - . .• - : / . ~ I " t ' . " : ' ' : ! . .." ' . ' ". I .. ___ • __ "" 4 "" - - ' ; 1 . J " . i: J ~ · # ,. ~ ~, - . .• - : / . ~ I " t ' . " : ' ' : ! . .." ' . ' ". I .. . ::· - : ~ - . ' , _,. r· ·. .;:-:::~i~i;!iij/,/f!!J)j:)i;.J~;.;.-- • .. ~ :;-:.-:·,.,!ii·y·· ,~~~ ... , .. . // 7 ··~,,.); -i~J&"':t~;~~" 'S"'t'"';~"~t-~~,.., f~~ l~~=-~·~~~!? :-:~~~t:.-:~:-;~~~:'f~:-::~;::it:~;:~"'i:::;;:~:;~~!~~:t~~!~~~I[~~~~;:f~;:~::.:~~:~~t:?2~ .... . -;:.;.• ·.,...-:.-... ···.,.s··'"=--=.·- '~ .. - ......: . -..--·--~·-~F; ...- ,., __- .:· •- ~-..?':':%'·-· . .. ,..,._ -. ~ <:~z~?J:'·~·~3:%""'~~~~:-75;~~5~~v·r . \\. - ~~'ti --~·It~ c •. 'Figure 1. The electric organ arrangement in various electric fishes. The electric eel (a) has three organs (stippled area at top left): large main organ, smaller organ of Sachs behind it and organ of Hunter under i~~ediately neath. Nain organ and organ of Hunter appear. in cross section below. Arrow indicates direction of current flow in body of fish during electric discharge. .. In Mormyrus (b) organ is situated near tail. Organ of Nalapterurus (c) forms a mantle just under skin of fish. Electric skate (d) has organ in tail. Electric ray (e) has a kidney-shaped organ in each wing. Cross-sectional view shm-1s columns of electroplaques in organs. The direction of the dis charge (arrow) is perpendicular to the broad surface of ray. (After Grund fest, Figure 1 continued on next· page. 1960a~ - Figure 1 continued. ~ -----.-.--~ ~-----­ ----------.. - ... ----·------~----_..._.... .... __.. .. ~ ... ,--.-------- .......................... ., • --·· -~-.·-.-~-·w ..... _.~, .. ··- - I . I . v1 ~\J .-~~~ .· .t . ?-1--··--~··--·--:('''f .-•. -·. .. pv~- ;~ -... __ ..:_. .. ... .. "" a \ 7f ___; .... r'·~ ~ - Y' l ' ! ''('-1 i . \ /1---r--·-r-~ '\J l T i ~ ~~-~[·--r_ ~t~'SJ I ·. · f .. ":-· --·--· -- >-\j I • ···•..r• .--. ---Ir '. ...-· - ; i ! .• • \ .. STALK ' \ : i : i I PENETRATING STALK . (: -~,;~- -~; :·-'::' '·.;"::·', .,._.: ·,) '~~~~G~- MULTIPlE STALK b Figure 2 Details of electric organ of electric rays (a), mormyrids (b) and elec tric eel (c) are shown. Electroplaque columns are vertical in body of the ray (top right). Nerve terminals (colored branching at top left) The document is a typed page with text content. There are no photographs, handwritten annotations, signatures, stamps, forms, diagrams, schematics, organizational charts, tables, or structured data visible on this page. There are also no redactions or visual evidence of experimental procedures, equipment, or facilities. The page appears to be purely textual, consisting of an introduction to a scientific topic. STALK . (: -~,;~- -~; :·-'::' '·.;"::·', .,._.: ·,) '~~~~G~- MULTIPlE STALK b Figure 2 Details of electric organ of electric rays (a), mormyrids (b) and elec tric eel (c) are shown. Electroplaque columns are vertical in body of the ray (top right). Nerve terminals (colored branching at top left) directly innervate column. Cranial nerves (heavy colored lines at right) connect organs with elec tric lobes (solid colored area) of brain.·. Recently discovered accessory organ is found only in ray genus Narcine. ~~ong different mormyrid species electro plaques are indirectly innervated via three types of stalk. As in some other fishes, uninnervated membranes of electroplaques in main organ of eel are con voluted. (After Grundfes t, 1960a). ----~--------- .. . : .. . · • lrigeminol ... ,. ., ·. (a) (b) ·. . • -~ (c) (d) Figure 3. Samples of organ and electroplaque structure. (a) Column of electro plaques in series array, representing essentially the arrangement in the torpe dine electric fishes and in Astroscopus. (b) Dorsal vietv of innervation which applies to Torpedo and main organ of Narcine; innervation is by individual nerve fibers to ventral surface of each electroplaque entering four different points of the periphery and supplying a limited area of the surface. In Astra scopus and the accessory organ of Narcine innervation is on the rostral surface, and nerve supply is more complicated. Figure also applies to Torpedo, except that accessory organ is absent. (c) Diagrammatic view of series and parallel_ arrays of electroplaques in the electric eel. A somewhat similar series-parallel arrangement occurs in other electric fish in which one surface is innervated. In Raia innervation is on rostral surfaces. (d) The mormyrid electroplaques are innervated on one or several stalk processes which form from branches that arise in the caudal surface of each electroplaque. In some, branches penetrate through the electroplaque body and inner1ation is then ahead of the electroplaque. In 1-ialapterurus there is only a single stalk which arises from the center of the caudal face of the electroplaque. (After Grundfest, 1960b). •.· --- ---------------- - Table 1. Anatomy of elcctroplaque in several electric fish. (After Grund fest, 196( . ... . S.p ecies• Ori:;in Inner- Dimensions '~o.in co ~ l o u . m o n ( s 'f (muscle) vatiou• Orientation R-C D-V 1\1-Lt columns per sidt' Torp.:do nobiliana Ilrandaial v D-V 8mm 10,. 8 nun 1000 1000 Nardne This page contains densely typed text, broken into paragraphs and sections with headings. There are no photographs, diagrams, stamps, forms, or handwritten annotations visible. The text discusses electroplaques, which are cells that make up electric organs in fish. The descriptions of electroplaques and their organization within the electric organs are detailed and technical. The page has a clean, document-like appearance with no visual distractions or experimental evidence. The page contains a scientific illustration of various electric fish, labeled as Figure 1, depicting the arrangement of their electric organs. The illustration includes drawings of an electric eel, a Mormyrus, a Malapterurus, a different type of electric fish with an arrow indicating current flow, and an electric skate. Several labels, such as 'a', 'b', 'c', and 'd', are present next to the respective fish. The illustration is accompanied by a detailed textual description that explains the anatomy and function of the electric organs in each fish. There are no photographs, handwritten annotations, official stamps, or redacted content visible on this page. in several electric fish. (After Grund fest, 196( . ... . S.p ecies• Ori:;in Inner- Dimensions '~o.in co ~ l o u . m o n ( s 'f (muscle) vatiou• Orientation R-C D-V 1\1-Lt columns per sidt' Torp.:do nobiliana Ilrandaial v D-V 8mm 10,. 8 nun 1000 1000 Nardne 6rasilitnsis Main organ Branchial v D-V 4mm 10" 4mm 500 400 Accessory organ Branch in I D Oblique 4mm !0" 4mm !!00 10 Raia clat"ala Skeletal R R-C ·200 1.2 Aslroscopus y-grar:cum .Ocular D D-\' IOmm 50" IOmm 200 20 Eltclrophorus .c tltclricus Skeletal R-C 200" I mm lSmm 6000 1S Eigtnmannia oirtsctns Skeletal c R-C 2mm 200" 200" 5 Sternopygus tlegans Skeletal c R-C 1mm 60" 60,. IS Gymno!us carapo Skeletal RandC R-C !!00 " 500" 500" 80 4 Sternarchus albzfrons ~ ~ R-C Gnathonemus com- pressiroslris Skeletal c c R-C so I' lOmm Smm 100 2 ~formyrus rume Skeletal R-C so I' 10mm Smm 100 2 Gymnarchus niloticus Skeletal c R-C 100 I' 100 I' 100 I' 140 4 Malaptr:rurus c tlectricus · ~ R-C 40" lmm 1mm 3000 ISOO • Abbre,·iations are R, rostral; C, caudal; D. dorsal; an .. d . \', ventral. f l\ledial-litteral• Electrophysiology The electroplaques in each column of an electric organ form a series array, so that the hook-up in series adds the outputs of the cells and builds up the voltage, Yhile the arrangement of columns of electroplaques in parallel functions to build up the amperage. "The large area of the organ of the strongly electric fishes is analoaous to the large number of plates in a storage battery cell of high current output" (Grundfest, 1967, p. 405). The discharge characteristics of electroplaques in several fishes are outlined in Table 2 • . In the electroplaques of marine electric fish, only the innervated surface of the cell is reactive. Electrogenic activity cannot be evoked by direct elec trical stimulation, but only by stimulating the nerve or Yith chemical agents, i.e., the cell is electrically inexcitable. The electroplaque's cell membrane, like that of the nerve or muscle cell, is selectively permeable to potassium ions but not to sodium ions, so that the higher concentration of the former in side the cell membrane and the latter outside the cell creates a resting poten tial across the membrane , with the inside negative and the outside positive. After a stimulus is applied, the permeability The document displays a monochromatic illustration featuring two distinct fish specimens, likely related to a scientific or biological study. The larger specimen is a flattened, disk-shaped fish, possibly a ray or skate, depicted in a dorsal view with intricate line work and shading indicating its fins, eyes, and gills. A smaller, more elongated fish, resembling an eel, is shown in profile in the upper portion of the page. Additional, smaller diagrams of fish anatomy are also present. Text at the bottom denotes "Figure 1 continued." There is no other visible content, such as stamps, handwriting, or experimental procedures. potassium ions but not to sodium ions, so that the higher concentration of the former in side the cell membrane and the latter outside the cell creates a resting poten tial across the membrane , with the inside negative and the outside positive. After a stimulus is applied, the permeability of the membrane changes, permitting the movement of both types of ions (and,- therefore, an electric current) to floY across the membrane. Generally, only the innervated membrane of the electroplaque - - Table 2. Electroplaque discharge and response characteristics in several elec- tric fish. (After Grundfest. 1960 b.) Respon-o;e • Dur:1tion, msec: y Species Dischu~e Post- Amplitude, Ampli- syn:Jptic: volts Form Frequency tude, mv Type* potential Spike Torptdo nobiliana 60 Monophasic Repetitive on Max. SO 1 5 None excil:ltion Narci~ brc:silitnsil Main orsan . 30 Monophasic Repelith·e on Max.S(} 1 5 None excil:ltion Accessory or;an 0.5 Monophasic Repetitive on Max. SO 1 s None , .. excit."ltion Raia. tlarola. ·4 Monophasic Repetitive on Max. SO 1 2S "None excit3tion Aslroscopus ;y-f]raccum 7 Monophasic Repetitive on ~fax. SO 1 s None excitation Electrophorus tleclricw 100 Monophasic Repetith·e on ~fin. 100 2 %+ 2+ excita lion · Eigrnmannia rirts~ens 1 Monophasic 250/sec: 1\Iin. 100 % 1 : . posith·e ; direct. current. SltrMp;ygus tltgans 1 Monophasic SO/sec Min. 100 2 2 10 positive direct current Gymnolu1 rarapo 1 Triphasic 50/sec Min. 100 3 1.5 1 Slernarchus albifrons 1 ·Diphnsic 750/sec: Min. 100 3 Gnathontmus rom-· prts:siroslris 10 Diphasic Variable Min. 100 4 0.% s ./.Iormyrus rumt 12 Diphasic: Variable Min. 100 4 Gymnarchus nilo!icw Low ~fonophasic 300/sec ~ ~ .. Malaplerurus tltdricw 300 Monophasic Repetitive on Min. 100 4 2 excitation • Response types: 1, electrically inexcitable electroplaques which produce only a posts}·nlptic potential and only on the innervuted surface: !!, responses are both postsynaptit.: potentials and 5pikes, produced only at in nervated surface; 3, opposite, uninnervated surf'!~e also is electrically excitable, producin~ a spike, whereas the . innervuted surface develops both a pnstsynuptic potcnti:ll and a spike; -t, the synaptic junction is at a distance rrorn the Inajor surfaces of the electrophque on one or several st;1lks produced by the caudal surface, and both major $Urfaces produce spikes. . . .. - .·· is affected. The opposite membrane usually remains inactive, maintaining a ne gative potential and offering little resistance to the flow of electric current. Inasmuch as current flows from electrophque on one or several st;1lks produced by the caudal surface, and both major $Urfaces produce spikes. . . .. - .·· is affected. The opposite membrane usually remains inactive, maintaining a ne gative potential and offering little resistance to the flow of electric current. Inasmuch as current flows from positive to negative, the orientation of the · electroplaque determines the current's direction in the fish. For example, ·the innervated surfaces of the eel's electroplaques all face the tail, so that cur rent flows from tail to head inside the fish and from head to tail in the water to complete the circuit. "The great number of electroplaques in series enables the eel to produce the voltage necessary to overcome the high resistance of its freshwater environment. The columns in parallel enable it to generate a cur rent, in brief pulses. of about one so that even in fresh water the or ~~pere. gan generates considerable pot-rer. The electric rays, living in salt water, show a corresponding adaptation to the lo\ver resistance of this medium. The giant ray Torpedo nobiliana has up to 1,000 elect"roplaques in series • much fe\.rer than the eel, and so generates a lower voltage. But it has some 2,000 columns in .. parallel in each organ, g1v1ng it its extraordinary amperage " (Grundfest, 1960a, p. 119). ; The generation of electricity in electroplaque oem~ranes considered as batteries is shown in Figure 4. ,· •, ,--'::'··---- ----, , . ... ' ~· Lla ·-· .r tb_ · . I, "• +p. ... I . . ___!__;- • -·-·-- ~ -~ • ~+ UNINNERVATED MEMS::tA.NE : !ELECTRICALLY INcXCITASLEI •i -; ;;.: •. ~ • - . l "] t·_'~----- J :. - . : .. I____ [. .- - ···.·-. ----·--. Io . : .. -:;::- ~- r INNERVATED MEMBRANE .. .· . I' .· !ELECTRICALLY INEXCITABLEI . L .J... . i. - .i &, ••• --. .... ~ I -:, ··:~· .. :·: ~--~··· ..... ·, --~ · . .2 ft 2b r -:.- . _!_.:.; --- ·~: ! -f .. UNINNERVATED MEMoRANE ~: (ELECTRICALLY INEXCITABLEI ___ .. -- •I r-·.:·~---~--- ~--- t .. ... -- . T ..... ··---- l r!. ... ·. .· "'! ••••• _,_ ..... ·-::;..: ·-·--.-..• - • .. . . -· .--· ::.1_- -· ' ·--~ I· . ·. ~ + INNERVATED MEMoRANE ···.-· ~ .T ··: !ELECTRICALLY EXCITABLE! i The page displays technical illustrations of electric organs from fish, labeled "a," "b," and "c," with detailed diagrams of electroplaques, nerve terminals, and internal anatomy. A caption below these figures describes the electric organs of electric rays, mormyrids, and electric eels, referencing their innervation and recent discoveries in the genus Narcine, citing "Grundfest, 1960a." The image also contains scattered small, dark dots that appear to be part of the original document's texture or printing, and faint, gray, horizontal lines that suggest a ruled or gridded background. There are no photographs, stamps, forms, or handwritten annotations visible on this page. ___ .. -- •I r-·.:·~---~--- ~--- t .. ... -- . T ..... ··---- l r!. ... ·. .· "'! ••••• _,_ ..... ·-::;..: ·-·--.-..• - • .. . . -· .--· ::.1_- -· ' ·--~ I· . ·. ~ + INNERVATED MEMoRANE ···.-· ~ .T ··: !ELECTRICALLY EXCITABLE! i ..:..J_ . ·~ . i . . . . . . . . ·- .. :-:--r-:- . ..... :.:1 T---... --··• -- .... L- ,;~ •.: ..::.. ____ ;_ ,· 3a 3b , ... --------.- --~l. ·-·---~- . '5_- . UNINNERVATED MEMot>.ANE I !ELECTRICALLY EXCITABLE! . ;_·_ -_ :.:.._-... :.. - ..- r: -~---- . I ~·. .~ I I I r~·······~·-···. - ':. : L.. r ' .. ~ --- -· _ .. : ~ · - i ~. .L . -~ I . ~ INNERVATED MEMSRANE ~ : . + !ELECTRICALLY EXCITABLE! .. L· ...... ·- . -r--:- . ._,_... • . . ,.:::I::..e , _______ · _ • : _ __- ;f I Figure 4. The generation of electricity by electric fishes can be explained by comparing electroplaque membranes (shaded areas) to batteries. Resting poten tials of membrane batteries, negatively ch~rged on inner surface and positively charged on outer, are shm-m at left. In marine fishes nerve stimulus short-cir cuits battery of innervated membrane (lb). }-Jagnitude of discharge equals resting potential, and current (broken line) flm.;s through electroplaque, then through external medium. In eel, stimulus reverses polarity of battery of electrically , ,... " - III. .Al.'m DETECTION WITH ELECTRIC FIELDS NAVIGATIO~ I The gymnarchus has a weak electric organ which.is somewhat like the power ful electric organs of the electric eels and other fishes in that it is derived from muscle tissue •. But until recently, no one had found a function for weak electric organs. Not-r it is knmm that "gymnarchus lives in a world totally alien to man: its most important sense is an electric one, different from any we possess" (Lissmann, 1963, p. 359). By means of this sense, it is able to swim uith equal facility backward or forward, and to avoid obstacles when they are encountered fore.·or aft·. Its movements are made with great precision, and •it never bumps into the walls of its tank when darting after small fish. The small electric organ of gymnarchus consists of four thin spindles con taining electroplaques running up each of its sides to This page features a scientific illustration detailing the structure and innervation of electroplaques in electric fish. It includes diagrams labeled (a) through (d) depicting these structures and their neural connections, with some labels pointing to specific anatomical parts. There are no photographs of people, locations, equipment, or subjects, nor any handwritten annotations, signatures, stamps, forms, or tables. Redactions or obscured content are not present on this page. The visual content focuses solely on presenting biological diagrams and their accompanying labels. obstacles when they are encountered fore.·or aft·. Its movements are made with great precision, and •it never bumps into the walls of its tank when darting after small fish. The small electric organ of gymnarchus consists of four thin spindles con taining electroplaques running up each of its sides to a point just beyond the middle of its body. The characteristics of its electric organ discharge vary ·with the individual and -.;-rith temperature. For example, specimens may produce voltages of 3 to 7, with a discharge frequency averaging about 300 cycles per second.* "During each discharge the tip of its tail becomes momentarily nega tive with respect to the head. The electric current may thus be pictured as s spreading out into the surrounding water in the pattern of lines that describes a dipole field (Figure 5). The exact configuration of the electric field depends on the conductivity of the water and on the distortions introduced in the field by objects tV'i th electrical conductivity different from that of the water. In a large volume of water containing no objects the field is symmetrical. When objects are present, the lines of current will converge on those that have better conductivity and diverge from the poor conductors (Figure 6). Such objects alter the distribution of electric potential over the surface of the fish" (Lissmann, 1963, 362). If gymnarchus could perceive such changes, it would be able to de tect objects in its environment. --This it is able to do through skin perforations near its head which lead into tubes filled with a jelly-like substance. Since the jelly is a good conductor, it acts as a lense to focus the lines of electric current which converge from the water into the pores and are led to electric sense organs at the base of the tubes. ·All animals are sensitive to strong electric currents, but their response is to currents many thousands of times stronger than those effective in gymnarchus and gymnotus. The latter can readily learn to locate currents whose density is reduced to 2 x l0-5 ~A/cm2, as calculated from the response distance to the hor izontal movement of an electrostatic charge outside the aquarium. Even the elec trostatic charge of a plastic elicits a response in gymnarchus. The same co~b fish is able to detect the weak current flot-r from a horshoe-shaped copper wire when it is closed and dipped The document page displays a table titled "Table 1. Anatomy of electroplaque in several electric fish." The table contains columns for Species, Origin (muscle), Innervation, Orientation, Dimensions (R-C, D-V, M-Lt), Number of columns, and Number of columns per side. Below the table is a section titled "Electrophysiology" with descriptive text. There are no photographs, handwritten annotations, signatures, or official stamps visible on this page. The content is entirely text and structured data within the table. There is no visual evidence of experimental procedures, equipment, or facilities. response distance to the hor izontal movement of an electrostatic charge outside the aquarium. Even the elec trostatic charge of a plastic elicits a response in gymnarchus. The same co~b fish is able to detect the weak current flot-r from a horshoe-shaped copper wire when it is closed and dipped just belot-1 the surface. It is also possible for this fish to distinguish b~t\.;reen "geometrically identical objects t..rith differing electrical conductivities. Conversely, it cannot distinguish between dissimilar objects which modify the current distribution in a similar way" (Lis£mann and Nachin, 1958, p. 454). * Discharge frequencies usually increase it higher temperatures. - .. . ., • Figure 5. Electric field of Gvmnarchus and location of electric generating or gans are diagramed. Each electric discharge from organs in rear portion of body makes tail negative with respect to head. Most of the electric sensory pores or organs are in head region. Undistrubed electric field resembles a dipole field, as shown, but is more complex. The fish responds to changes in the distribution ' of electric potential over the surface of its body. The conductivity of objects .. <1ffects distribution of potential. (After Lissmann, 1963.) ---- -- ---·--------· -----·- ··-------· -------- -----·-- --·-----------·--:---·--·.._..------------·· --<P··-·--·'"-----.. - ~- --~-~ --~ -~·---- -----·-~---·~----- .. . .- ·~ Figure 6. Objects in electric field of Gymnarchus distort the lines of current f