horizontdly, t i i i d the iiit,wiitLl I i i n i i i w n w i i t tisnw of the shrinip waR
itsunlly direct c d ttowtiwltrd i i r i l t w t i r i iiiig:lc of inclinutioii of the body
exceedcd i h u t 50” with thc hOri~,0tlt,id plitii~. Dr W. 1). Clarke (personal
cornniiiiiic,ict,ioii) iiot,rd that uwurtns o f S . s i r n i h off California, observed
through t h window of submt~ait)k*, swttm gently in an oblique or
iic-arly vorticul positioii with t h c b head l i p . On the other hand, underwitter flash 1)hotogribl)hs of A”ergia lurcns suggested that the majority
of‘ this species wertb swimming in horizontiil positions (Ohta and Omori,
1 !I 7 4).
Neverthc4ess, if the ~:ountc~r-shucliiig hypothesis is valid for all
photophores of’ the upper mesopelagio shrimps, it must satisfy
intiny theort~ticd objections. For instance, the light emission of an
tuiimctl milet, be s h t d y and the mima1 must have the ability to adapt,
either by migrittion or controlling photophore funrtioning, to cyclic or
short term variiltionu in ambient light. Migration suggests itself as
the obvious brhavioural response by which an animal could maintain
itself in il constant light regime, but so far neither type of control has
been ciescribed in the shrimps. If the luminescence really serves as a
rec.ognition sigiiiLI by which individuuls of the same species maintain
(*ontact, iri Rwilrrning or ut mating, thr intcrprotation of the hypothesis
becomes difficult. The hypothch uppcitrs unlikely to explain the
f‘unction of photophores that o(:(:ur in the lower mesopelagic species.
I n the depths where the ariirnills are distributed the light produced
locally by the bioluminesoencc of living organisms could exceed the
prnetrntion of daylight, thereby rendering such R counter-shading
rnechttnism ineffective. The tlermal photophorcs may function as
light reflectors or receptors.
Foxtoii ( 1 970b) mentioned the rolc of rhromatophorev of semitmnsparent Rhrimpe in relation to the funotion of the photophores.
[n this connection, Sergin Zucens ilppcars to have the ability to control
the ohromntophoros in resj~on~e t o chitnges in background colour and
illutnincttioii. The shrimps (.aught near the surface during twilight are
Iurgely traiiapsrtwt, while those collecttad a t 200-300 m depths are more
heavily pigmented. The fuuct ion81 significance of the nniformly
pigmented red integument of the lower meso- and bathypelagic shrimps
is obscure exvept in so far as it renders the animals inconspicuous and
possibly aid8 in reducing the surface reflection of light produced by
iicarby orgtinisnis (k’oxton, 1970b).
W&h uncl Cliace ( 1937, 1938) studied the relationship bctwecn
thc vorticd distribution of certain specie8 of sergestids and oplophorids and the size and structure of their eyes, and found that
the eyes of sprcica in the genera Sergia, OpEopho~u~ and flt~~tellaspi8
itsunlly direct c d ttowtiwltrd i i r i l t w t i r i iiiig:lc of inclinutioii of the body
exceedcd i h u t 50” with thc hOri~,0tlt,id plitii~. Dr W. 1). Clarke (personal
cornniiiiiic,ict,ioii) iiot,rd that uwurtns o f S . s i r n i h off California, observed
through t h window of submt~ait)k*, swttm gently in an oblique or
iic-arly vorticul positioii with t h c b head l i p . On the other hand, underwitter flash 1)hotogribl)hs of A”ergia lurcns suggested that the majority
of‘ this species wertb swimming in horizontiil positions (Ohta and Omori,
1 !I 7 4).
Neverthc4ess, if the ~:ountc~r-shucliiig hypothesis is valid for all
photophores of’ the upper mesopelagio shrimps, it must satisfy
intiny theort~ticd objections. For instance, the light emission of an
tuiimctl milet, be s h t d y and the mima1 must have the ability to adapt,
either by migrittion or controlling photophore funrtioning, to cyclic or
short term variiltionu in ambient light. Migration suggests itself as
the obvious brhavioural response by which an animal could maintain
itself in il constant light regime, but so far neither type of control has
been ciescribed in the shrimps. If the luminescence really serves as a
rec.ognition sigiiiLI by which individuuls of the same species maintain
(*ontact, iri Rwilrrning or ut mating, thr intcrprotation of the hypothesis
becomes difficult. The hypothch uppcitrs unlikely to explain the
f‘unction of photophores that o(:(:ur in the lower mesopelagic species.
I n the depths where the ariirnills are distributed the light produced
locally by the bioluminesoencc of living organisms could exceed the
prnetrntion of daylight, thereby rendering such R counter-shading
rnechttnism ineffective. The tlermal photophorcs may function as
light reflectors or receptors.
Foxtoii ( 1 970b) mentioned the rolc of rhromatophorev of semitmnsparent Rhrimpe in relation to the funotion of the photophores.
[n this connection, Sergin Zucens ilppcars to have the ability to control
the ohromntophoros in resj~on~e t o chitnges in background colour and
illutnincttioii. The shrimps (.aught near the surface during twilight are
Iurgely traiiapsrtwt, while those collecttad a t 200-300 m depths are more
heavily pigmented. The fuuct ion81 significance of the nniformly
pigmented red integument of the lower meso- and bathypelagic shrimps
is obscure exvept in so far as it renders the animals inconspicuous and
possibly aid8 in reducing the surface reflection of light produced by
iicarby orgtinisnis (k’oxton, 1970b).
W&h uncl Cliace ( 1937, 1938) studied the relationship bctwecn
thc vorticd distribution of certain specie8 of sergestids and oplophorids and the size and structure of their eyes, and found that
the eyes of sprcica in the genera Sergia, OpEopho~u~ and flt~~tellaspi8