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Fig. 4. Ommatidial subtypes found in the dorsal rim area (DRA), dorsal and ventral
retina of butterflies according to opsin mRNA expression in individual
R1–8 photoreceptor cells (ovals). Photoreceptor cells are color coded
according to the identically colored visual pigments and opsins shown in Figs
2 and
3 that are expressed in them.
Question mark indicates that opsin expression is unknown in some parts of the
eyes reviewed here. Boxes indicate the UV, B and LW opsin genes and
lineage-specific duplicates present in each species and are organized into
columns according to membership in the UV, B or LW opsin clades shown in
Fig. 2. Note: the patterns of
opsin mRNA expression in the riodinid Apodemia mormo are unknown and
so are not included in this scheme. Left to right: D. plexippus DRA
is composed of approximately 100 ommatidia organized into two to three rows
that exclusively express the UV opsin (gray) in the R1–8 cells. Both the
dorsal and ventral eye contain three types of ommatidia in which the R1 and R2
cells express UV–UV, UV–B or B–B opsin mRNAs and the
R5–8 cells express a LW opsin (orange)
(Sauman et al., 2005). P.
rapae ventral eye contains four opsins and three ommatidial subtypes in
which R5–8 express one LW opsin mRNA (orange) and R1 and R2 express
UV–B, UV–UV or V–V (violet) opsin mRNA
(Arikawa et al., 2005). It is
not yet known whether other ommatidial subtypes are present in the dorsal
retina or in the DRA. L. rubidus dorsal eye contains three opsins and
is sexually dimorphic with respect to their expression. In males, R5–8
exclusively expresses the B1 (purple) opsin, while in females the B1 opsin is
co-expressed with the LW (orange) opsin. The R1 and R2 cells of the dorsal eye
are almost entirely UV–UV, with the R1 and R2 cells of a few ommatidia
expressing UV–B1 and even fewer expressing B1–B1. The ventral eye
of both males and females contains one additional opsin, B2, encoded by a
duplicate blue opsin gene, BRh2. The R3–8 cells all express the
LW opsin and R1 and R2 all express UV–B1, UV–UV, B1–B1,
UV–B2, B1–B2 or B2–B2
(Sison-Mangus et al., 2006).
P. xuthus contains a dorsal eye with four opsins and three distinct
ommatidial subtypes: B–B (dark purple) in R1 and R2 and PxRh2 (orange)
in R3–8; UV–B in R1 and R2, PxRh2 in R3 and R4, and PxRh3 (yellow)
in R5–8; UV–UV (gray) in R1 and R2, PxRh2 in R3 and R4, and
co-expressed PxRh2 and PxRh3 (orange–yellow). The ventral retina
contains five opsins and the same three ommatidial subtypes except PxRh1 is
co-expressed with PxRh2 (green–orange) in all R3 and R4 cells in the
ventral eye. Squares indicate opsin genes expressed in identically colored
photoreceptor cells.
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