Spectral sensitivity of the compound eyes in the purple land crab, Gecarcinus lateralis

Abstract

The spectral sensitivities(S(λ)) of dark-adapted compound eyes of the purple land crab Gecarcinus lateralis posses a broad maximum in the blue-green, 420-530 nm,when measured by electroretinographic (ERG) techniques. Selective adaptation experiments showed large changes in sensitivity but did not isolate different receptor types. A photopigment with maximal absorption at 487 nm was identified in the rhabdoms by microspectrophotometry. Besides the presence of a dominant green receptor system, the existence of a hump in the short wavenlegth region in S(λ) suggests the presence of a blue-sensitive system as well. It is hypothesized that two photo pigments (P487 and P440) in conjunction with screening pigment(s) mediate broad visual maximum in the blue-green in the purple land crab.