K. f’hotoltrc:! ic. itriplicuti,orhs
Aside fi-om one or two iq)orts 011 tlinofli~gellates, a11 the above
olwrvut ions leiid 11s to stibte t t i ; r t “ InigrcLtion ”, when present, consists
of ill1 II 1)w;~rd iiiovenl(!iit iij the inoriiing or (luring the day :md a d o w ~
wibrd niovemcnt in tlhe aftmnoou or ut, night. Thus positive phototwtism iiiiiy be offercd i ~ s u gtlnebrid explanation, in agreement with
HiLsI(1 (l!h%&), I{liple,y ct al. (10681)) m ( 1 others.
This is Riilwtiir1tiutid by liLhi*iLtol..V work on freshwater und marine
I’l’otiStiL. An c ~ d o g e ~ ~ o ~ s
circiitlii~n rhythm of pliotot~iLxis WAR first
establishetl t)y I’ohl ( 1 948) on 1b”rrgl~nn m i l since then h i ~ s bocn studied
in detuil (see for iiistnnce VoWild t ~ n d Ihvenport,, 1970). Id’or general
rovicaws on 1)tioIotiLxis in rinicelliiliir t i l g i w , Clikyton (1964) t ~ n d Nriltsch
( I $170) rniiy h c:oiisiiltd.
M o w work is ticctlctl on spwific rcy)rmxes of phytopltmktcrs to
liglit, stiriirili, li~llowing Nordli’s ( L!h57) first experimcnts. Action
spcat,ra Ii;ivcb 1)ccw stutlietl by Halldt~I ( 1 958) for threo Rpecies of rlinotlitgcllntcs. Akiniiis ( 1967) hru cwtirnatetl the threshold intensities for
two ot,lrcrs : ptiotot8iictism wus posithv from 400 to “ 1 000 ” (10 OOO?)
lux, zoro from 1 1 000 tjo 16 000 lux i d ncgntive at, 20 000 lux (photosynt h i 8 Iwiiig iticrrnsed, sat,rir:itctl tincl inhibited respectively).
l’liototi~xis is ;clso iiivolved in the circiuliun migrations of benthic
inicro-;tIgii(~ (sipit iLlitong recent works HopBins, 1966, and Round and
I?L~TII(T, I !)(;ti), so that vwticul inigriitions in both phytoplrinkton and
ph,ytobcn tlios nIiL.\i involvcl t i contntiw mechunisni .
I. Otlw r. irtiylicd icms
14wt, or illusion, us we askibil ;ibovca? I t might he iirgucd that
phyt,ol)liiiiktcrs ivcro ncvw w e n swiriiining u p and down i L t s a t by m y
ocit.:~no#r~ti)lic.!., i d ttmt avd:ihlc ” prooik ” consist in observing rnore
cells iit i~ given tlrpth m t l titnc ; t h u x , some other phcnorn(mon mriy
interfere itlid twing nbout an artifiwt of migration. In the author’s
opiiiion this c i ~ n be true in A O I I ~ C caws, but doea not invulidatc the
g c n c ~ ~ l
schrme. Let us play the dovii’s urlvocate.
( 1 ) If cells divide u t ti preferential clepth (related to an optimal
light levd) iit i~ givm tirnc, i t could be erroneously conclutletl that
t h y llttti migritttd there actively. Relntive 1 1 s well as ahsolute conc.entmtions stiouI(1 Iw considered. In the following cxaniplc a t least,
this criticitmi s w i t i s iiiviilid : the freshwilter C‘(1rutiunt observed by
N ~ i i i w w k ( 1 !)(i3) ~~~:tclierl its maximum division rate around 3 a.m.
when celh ~ v w t ~
(~wnly t h t ri1)utcd ill tho water column ; il prontinent
Aside fi-om one or two iq)orts 011 tlinofli~gellates, a11 the above
olwrvut ions leiid 11s to stibte t t i ; r t “ InigrcLtion ”, when present, consists
of ill1 II 1)w;~rd iiiovenl(!iit iij the inoriiing or (luring the day :md a d o w ~
wibrd niovemcnt in tlhe aftmnoou or ut, night. Thus positive phototwtism iiiiiy be offercd i ~ s u gtlnebrid explanation, in agreement with
HiLsI(1 (l!h%&), I{liple,y ct al. (10681)) m ( 1 others.
This is Riilwtiir1tiutid by liLhi*iLtol..V work on freshwater und marine
I’l’otiStiL. An c ~ d o g e ~ ~ o ~ s
circiitlii~n rhythm of pliotot~iLxis WAR first
establishetl t)y I’ohl ( 1 948) on 1b”rrgl~nn m i l since then h i ~ s bocn studied
in detuil (see for iiistnnce VoWild t ~ n d Ihvenport,, 1970). Id’or general
rovicaws on 1)tioIotiLxis in rinicelliiliir t i l g i w , Clikyton (1964) t ~ n d Nriltsch
( I $170) rniiy h c:oiisiiltd.
M o w work is ticctlctl on spwific rcy)rmxes of phytopltmktcrs to
liglit, stiriirili, li~llowing Nordli’s ( L!h57) first experimcnts. Action
spcat,ra Ii;ivcb 1)ccw stutlietl by Halldt~I ( 1 958) for threo Rpecies of rlinotlitgcllntcs. Akiniiis ( 1967) hru cwtirnatetl the threshold intensities for
two ot,lrcrs : ptiotot8iictism wus posithv from 400 to “ 1 000 ” (10 OOO?)
lux, zoro from 1 1 000 tjo 16 000 lux i d ncgntive at, 20 000 lux (photosynt h i 8 Iwiiig iticrrnsed, sat,rir:itctl tincl inhibited respectively).
l’liototi~xis is ;clso iiivolved in the circiuliun migrations of benthic
inicro-;tIgii(~ (sipit iLlitong recent works HopBins, 1966, and Round and
I?L~TII(T, I !)(;ti), so that vwticul inigriitions in both phytoplrinkton and
ph,ytobcn tlios nIiL.\i involvcl t i contntiw mechunisni .
I. Otlw r. irtiylicd icms
14wt, or illusion, us we askibil ;ibovca? I t might he iirgucd that
phyt,ol)liiiiktcrs ivcro ncvw w e n swiriiining u p and down i L t s a t by m y
ocit.:~no#r~ti)lic.!., i d ttmt avd:ihlc ” prooik ” consist in observing rnore
cells iit i~ given tlrpth m t l titnc ; t h u x , some other phcnorn(mon mriy
interfere itlid twing nbout an artifiwt of migration. In the author’s
opiiiion this c i ~ n be true in A O I I ~ C caws, but doea not invulidatc the
g c n c ~ ~ l
schrme. Let us play the dovii’s urlvocate.
( 1 ) If cells divide u t ti preferential clepth (related to an optimal
light levd) iit i~ givm tirnc, i t could be erroneously conclutletl that
t h y llttti migritttd there actively. Relntive 1 1 s well as ahsolute conc.entmtions stiouI(1 Iw considered. In the following cxaniplc a t least,
this criticitmi s w i t i s iiiviilid : the freshwilter C‘(1rutiunt observed by
N ~ i i i w w k ( 1 !)(i3) ~~~:tclierl its maximum division rate around 3 a.m.
when celh ~ v w t ~
(~wnly t h t ri1)utcd ill tho water column ; il prontinent