▁the ▁visual ▁prote ins ▁are ▁also ▁tight ly ▁pack ed ▁into ▁the ▁micro v ill ar ▁space , ▁leaving ▁little ▁room ▁for ▁cy top las m . ▁ ▁The ▁phot ore cept ors ▁in ▁D ros oph ila ▁express ▁a ▁variety ▁of ▁rh od ops in ▁is o forms . ▁The ▁R 1 - R 6 ▁phot ore ceptor ▁cells ▁express ▁rh od ops in 1 ▁( R h 1 ), ▁which ▁absor bs ▁blue ▁light ▁( 4 8 0   nm ). ▁The ▁R 7 ▁and ▁R 8 ▁cells ▁express ▁a ▁combination ▁of ▁either ▁Rh 3 ▁or ▁Rh 4 , ▁which ▁abs orb ▁U V ▁light ▁( 3 4 5   nm ▁and ▁ 3 7 5   nm ), ▁and ▁Rh 5 ▁or ▁Rh 6 , ▁which ▁abs orb ▁blue ▁( 4 3 7   nm ) ▁and ▁green ▁( 5 0 8   nm ) ▁light , ▁respectively . ▁Each ▁rh od ops in ▁mole c ule ▁consists ▁of ▁an ▁o ps in ▁protein ▁c oval ently ▁linked ▁to ▁a ▁car oten oid ▁chrom oph ore , ▁ 1 1 - cis - 3 - h ydro xy ret inal . ▁ ▁As ▁in ▁verte br ate ▁vision , ▁visual ▁trans du ction ▁in ▁in verte br ates ▁occurs ▁via ▁a ▁G ▁protein - cou ple d ▁path way . ▁However , ▁in ▁verte br ates , ▁the ▁G ▁protein ▁is ▁trans du cin , ▁while ▁the ▁G ▁protein ▁in ▁in verte br ates ▁is ▁G q ▁( dg q