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Fig. 4. Spectral sensitivities of Pieris photoreceptors and absorbance
spectra of screening pigments. (A) Log spectral sensitivity data (error bars
are S.E.M.) of green sensitive photoreceptors determined by
intracellular recordings of R3,4 photoreceptors of type I and III ommatidia
(open symbols; L560) and type II ommatidia (filled symbols; L560-II); from Qiu
and Arikawa (2003a). The
continuous green line gives the absorption spectrum of a visual pigment with
peak absorption at 563 nm. (B) Log spectral sensitivity data (error bars are
S.E.M.) determined by intracellular recordings on R5–8
photoreceptors of type I and III ommatidia (open symbols; L620) and type II
ommatidia (filled symbols; L640); from Qiu and Arikawa
(2003b). The dashed and dotted
lines give log(1–Tp) and
log(1+Tp), respectively, where Tp is
the transmittance of the proximal rhabdom tier, length
Lp=150 µm, diameter Dr=2.0 µm,
with a visual pigment R563, with maximum absorption coefficient
max=0.006 µm–1, in all R5–8
photoreceptors. The dot/dash green line gives the absorbance due to the visual
pigment in photoreceptors R3 and R4 of the distal rhabdom tier,
Adv=–log(Tdv), where
Tdv is the transmittance. The summed volume fraction of R3
and R4 is assumed to be f3,4=0.3 (see Materials and
methods). The used spectral sensitivity data are normalized to the peak value,
meaning that the log sensitivity data have a zero peak value. The log
sensitivity data of L620 and L640 were shifted 0.66 and 1.1 log unit,
respectively, to fit the log (1–Tp) spectrum at the
longest four (L620) or three (L640) wavelength values. (C) Absorbance spectra
of screening pigments in the pale-red (PR) ommatidia and the deep-red (DR)
ommatidia derived by subtracting the log spectral sensitivities of L620 and
L640 from the log (1–Tp) spectrum; the error bars
are taken to be identical to those in B.
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