j *@ - Sociedade Brasileira de Psicologia

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smdal set of pnmary colours (Backhnus & Menzel, 19d7). 'lNs physiologcal chromaticity
diagram shows thi sm ctral colours in a plane of constant çtbee-bfightness''.
Backhaus & Menzel (1987) derived a model . calculation in which the
perceptual distance of colour signp e4n be determined from the spectral and intrinsic
noise properties of the photoreceptors. The resolution of one photoreceptor is limited
by nuctuations of the recejtor potential. These fluduations are caused by the photon
absorption process and the transduction process (shot noise and transducer noise,
Ixqughlin, 1981). The intrinsic noise componqnts in Apis me lfera reach 0.4% of the
rnaxim lm voltage response, the =me value wâs aWumed for all species. '
For equaly bright spectral lights, the pjnd stem are counted for chnnges of
the smctral lights in 4nm steps. dne pjnd is reached if one of the three receptor
Potentials
changes signifio ntly with respect to the noise components.
U ULTS
The recorded cels showed a resting potential of -40mV to -K mV and à
depolarizing potential with a phasic-tonic time course to lil t' stimuli of diferent
intensities. In some species, discrete potential fluctmtions (quantum bumps) appeared
at very 1ow intensities. The avqrage S(X) of the photorecejtors of the different species
are similar to each other. Most of the species have three receptor types : the UVreceptors,
with maximnl sensitivity at 336 nm ? show 1ow sensitivity . (1-2%) above
450nm and this would appear to be physioloscal in comparison with the model
cal culation
and behavioural iests of colour discriminability. The blue receptors have
their maximal sensitivity at 432nm, and some ' of these receptors ' show high sensitivi jy
(up to 50*) below 370nm. 'l'à e Joisible
explahation for this is either electrical or
artifactual coupling between the UV and blue receptor or the #-peak of the photopim
ent, which Menzel tt al. (1988a) asumed for Osmia rlz/J. the S(X) of the green
receptors follow the theoretical absoyption function of a rhpdoplin pigment with the
corresponding àmax' W e malimum of these receptors are at about 53inm, and 370
,
nm for a iecohd @-j peak.
n ree specles have an additional red receptor with maximnl sensitivity at
Konm and a J-peak at j60nm, but the fldions in Tenthredo are much narrower
as the theoretical Dartnal-functions (see below) predict. '
Although the spedral sensitikties 'of the spedes are similar the V hfunctions
show some differekces. M nnimals are ablé to discriminati violet and bluepeen
colours very wel. However, b0th the worker bee and àrone bee are beter in
'
discnminating blue-pee il co 1 otlrs, whilst
Osmia m/J an' d sole bu' mblebees distinguish
better in the violet part of the spectrum . '
n e spectral sensitivities of the photoreceptors of the worker bee were
measured with diferent methods. Autrlzm & v-zweltl (1964) and Menzel & Blakers