2 OPSINS FROM THE COMPOUND EYE OF THE CRAB HEMIGRAPSUS-SANGUINEUS

The primary structures of two opsins from the brachyuran crab Hemigrap sus sanguineus were deduced from the cDNA nucleotide sequences. Both d educed proteins were composed of 377 amino acid residues and included residues highly conserved in visual pigments of other species, and the proteins were 75 % identical to each other. The distribution of opsin transcripts in the compound eye, determined by in situ hybridization, suggested that the mRNAs of the two opsins were expressed simultaneou sly in all of the seven retinular cells (R1-R7) forming the main rhabd om in each ommatidium. Two different visual pigments may be present in one photoreceptor cell in this brachyuran crab. The spectral sensitiv ity of the compound eye was also determined by recording the electrore tinogram. The compound eye was maximally sensitive at about 480 nm. Th ese and previous findings suggest that both opsins of this brachyuran crab produce visual pigments with maximal absorption blue-green region of the spectrum. Evidence is presented that crustaceans possess multi ple pigment systems for vision.