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<br />1. Threshold of the anode reaction. The
<br />f d 10 most marked anode reaction was
<br />s::: wa ~~raexperiments on Black Sea fishes. In general it is manifested in the
<br />swim T 11 species. At threshold values of the current the fish t d
<br />to the anode and remain near it (b i h urn aroun .
<br />tt.e of the action of the ump nto t e anode) throughout the entire
<br />case the fish retain theirc~~~~~~tor ~ntil electronarcosis sets in. In the latter
<br />to move towards the anode Breat r 0 some time, expressed ,in periodic attempts
<br />Once the current is ,switched off ~h:gf~~~t;nu~~i although it becomes arrhythmic.
<br />without any noticeable after-effe .' , . ap1 y resume their former activi ty
<br />violent .the. anode reaction and th~t:~re T;:pgi~elatelr the current intensity, the more
<br />y e ectronarcosis sets in.
<br />
<br />anod;h:u~e:~~~~rs~~ t~e viviparous blenny, which turns distinct~y towards the
<br />With an i i gg1shly in its .direction, deviates somewhat from this pattern
<br />nc~ease D voltage the extent of the transverse flexures of th b d . .
<br />;~:~:/~~~~=:~:b~~, ~ut t1'e fish does not in fact move from the spot. eA ~trl~n-
<br />and moves. towards itV ltag~ prevents movement; it cannot turn towards the anode
<br />a field of pulsed cur~:~; ;~;~~. (F~r:;mii;~4~hen~me~~n i~ ~escribed in the eel in
<br />has remadned in a state f ,. n e v V1parous blenny, which
<br />anode fl i 0 tetanus, the anode reaction disappears and only the
<br />eXure rema DS.
<br />
<br />At Fish S~owing no" anode reaction wi th an increase in voltage behaved 'Variously
<br />a cerra n ~oltage such species as the bream and reef-fish swam swiftly now to'
<br />one, now to t e"other electrode. Swimming towards the cathode was more difficult
<br />~= ~owardis the anode. Typical behavior was observed during actlon of the cur-
<br />n an nterval at values. provoking a sHmuT .(f' h )
<br />authors with. the sole diff. h ' us r1g. t described by many
<br />. ' ..." ., .. . erence ,t j't no anode reaction occurred whatevf'~ the
<br />1ncre.ase in current., .The pi.pe.fish perform. ed sharp fIe. d . 1 ".
<br />the bod iT' ... . , .. xures an rotatJ.OllS around
<br />thedir~c:{o~'Of~~/:::~;~el i\httached t~ anything by the-rail, inclined in
<br />
<br />other ~is~. the sole p~rfo~e~ ~ot:~i~::e:n : ~:;:~~~l i;~~n:. sp~:I;'Bl~~~i~:a the
<br />
<br />~~~~ h1~i W~th a.f1eld intensity close to the 'tetanus threshold, all the
<br />the ~'B~::k s::et~r~aJ.~ing ~ea~ and tai: upward~. And yet in onespec1men of
<br />,ota dJ.st~nct turn1ng . and 1mpetuous movement to the anode
<br />~~:~~:~r:~d~ Th~other specJ.es either bent in the direction of the anode {anode
<br />urne ,fowards it, making short darts, frequently towards the wall of
<br />j'
<br />
<br />
<br />Reaction and Tetanus
<br />
<br />',-
<br />
<br />
<br />Anode re-I
<br />action- Tetanus
<br />
<br />s~ cies
<br />
<br />9.3:0,3
<br />7.2:0,3
<br />6,3:0,1
<br />U,I:O,6
<br />4,2:0,7
<br />6.2:0.3
<br />4.2:0,5
<br />6,3:0,6
<br />15,0:0,9
<br />'B.B:2,4.
<br />5;9~O,5.. 21,4:i:O,9
<br />Fish showning no anode reaction
<br />
<br />H-tB
<br />.'8-10
<br />18
<br />18
<br />22
<br />18-19
<br />18
<br />
<br />13'-15
<br />17
<br />8
<br />8
<br />17
<br />14
<br />B
<br />
<br />1,88-2,14
<br />1,88-1,~
<br />1,20
<br />1,20
<br />2,61
<br />2,01-2.05
<br />1,20
<br />
<br />:g::::~ 69.3:0.7 20 17 2.37
<br />14-23 13,5". g;~=!,32 19-.,21 16-17 2,32:"'2,55
<br />3 ,I:.. <>' 18 2,04
<br />f6:::~~ 63,2:1,1 18 14 2,00
<br />15,0: 1,5 18-22 13-17 1,88-2,40
<br />H..,21 14,4: 1,5 .18 8 1,20
<br />
<br />No~** .Reac~on noted. in 4 specimens only. **Reae-ticn noted in 5 cimens
<br />oaIy. ReaCtlOD noted In 1 specimen only (explanation in text). spe
<br />
<br />136
<br />
<br />
<br />
<br />the aquarium with subsequent concealment (round goby, Black Sea blenny, scorpion-
<br />fish, star~azer). If the stargazer was oriented with the head towards the cathode'
<br />strictly along the lines of force, it did not turn towards the anode and responded
<br />to the switching on of the current only by spreading the oppercula and .fins. One
<br />goby responded with a distinct anode reaction which was not repeated with subse-
<br />quent switching on of the current. A yoimg scorpion fish 6 cm in size responded,
<br />if in an open place, by a distinct anode reaction; if near the wall of the aqua-
<br />rium it hid, adopting a threat posture. After the current had been switched on
<br />several times it began to move towards the anode and away from the wall. No anode
<br />reaction was found in the shorthorn sculpin. Its behavior is 'similar to that of
<br />the Black S~a round goby in an electric field.
<br />
<br />The intermediate group of fish deserves ,particular attention. All the speci-
<br />mens of, the surmullet caught in spring and summer in Kerch Strait, showed ,an anode
<br />reaction. Of the 18 specimens investigated in February in the. region of Anakliya
<br />(Caucasus), only 10 moved unswervingly to~ards the anode and out of 9 specimens
<br />of fish from the Batumiregion (in October) only 4 preferred the anode (Table).
<br />The others either swam swiftly around the aquarium, stopping in turn at one or
<br />the other of the electrodes, or went to neither of them.
<br />
<br />All the specimens of the greater weever"caught in the same month as 'the sur-
<br />mullet and also off Batumi, responded with a completely clear anode reaction
<br />Crable) but .2 specimens caught off Novi Afonin December responded to the switch-
<br />ing on of the current merely by hiding and adopting a threaf'posture.
<br />
<br />Of the 10 specimens of the fopnder only 5 turned distinctly towards the anode
<br />and reached 'it. The others merely made swimming movements, without moving from
<br />the spot and without being able either to turn towards the. anode or move away
<br />from the bottom. The dab is. a subspecies of the Baltic. flounder;.bowever, as we
<br />can see from the data given in the ,Table, the behavior of ,this fish. is .quite dif-
<br />ferent. In this sense the Baltic subspecies is similar in its behavior in an
<br />electric. field to the Black Sea specimens of the greater weever and the surmullet.
<br />
<br />.Ii' sh~uld al~o.b~ noted that in spite of th~,-absenc~ of an anode reaction
<br />in bottom and demersal fishes, all the. species distinguished the polarity of the
<br />electric field and preferred the descending flo~ to the ascending flow.
<br />
<br />2.,> Tetanus threshold. Values of .field intensity provoking tetanus exert the
<br />strongest cur.rent action on.fishin pur experiments. . It is manifested similarly
<br />in all species of fish: .the body is tense, thef.ins spread, the opercula are
<br />wide open and breathing ceases.. This. state continued for .some time after the
<br />current was switched off. in direct relation to the duration of current action.
<br />Breathing is not renewed immediately after the current .ceases and at the beginn.ing
<br />it is manifested only in jaw movements with open opercula. Sometimes the fish ap-
<br />pears'I to sh~ke ,".itself~, ' -,', -
<br />
<br />ThIi . threshold of the reactions .in dif'f';rent'spe:~:i';!l)'tIlaidiffer si~iUcknf1y'
<br />and it:does~ot depend on thedegree.of'cresist~nce?f,afishto:.c:urre.~t; ,Thus in
<br />the surmullet, bream and sole the. tetanus, threshold is highest "and .its va1.ues
<br />similar, as also the size of .the fish (Table). At the same time after.2 - 3.in'-
<br />puts (in succesdon)' of ,a .$trongcurrent, ,the surmulle~ "may die, the bream and
<br />the sole survive it withQut e,!,ident seri"usconsequ,e,nces." .' ,',
<br />
<br />In some fish an inverse' depend';nce is noted. In f,ish\!,ore resistant: to the
<br />current" the tetanus .threshold is lower. than in the less resistant: ones. .The
<br />reef-fish, the seahorse and the pipefish are:':weak fish"; their threshold ,is
<br />35.6,47.1, 25.8 VIm respectively. The dab, the round goby,the Bla,:,k Sea
<br />blenny,the scorp10n-fishand the stargazer are.very resistant; their thre~hold
<br />is between 15.0 and18.0.V/m: The same is also observed in Baltic fishes: in
<br />lhe vimba, the~ivip~rous blenny.and flounder the thresh;'ldis 20 VIm, and in the
<br />shorthorn sculpin 14.4 VIm (Table). .
<br />
<br />,l,et us aiso indicate the difference in threshold with the different orienta-
<br />tion of the fish. Thus is.a scal in an ascending. flow. the tetanus threshold is
<br />
<br />137
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