Eye structure and function in the giant freshwater prawn Macrobrachium rosenbergii

Abstract

We used histological and electroretinogram methods to investigate eye structure and function in Macrobrachium rosenbergii. M. rosenbergii was demonstrated to have superposition compound eyes with a clear zone. Rhabdom volume dramatically increased only under dark-adapted conditions at night. The eyes were assumed to be dark adapted after about 50 min under dark conditions, and to be light adapted after about 4 min under light conditions during the day. The mean angle between receptor units was 1.75°. The slope of the visual sensitivity (V/log I) curve of M. rosenbergii was 0.40 and the K value (stimulus irradiance eliciting half of the maximum response) was 16.1 log photons cm−2 s−1. The mean dynamic range was 4.06, ranging from 13.91 to 17.97 log photons cm−2 s−1. The response latency was 19.6 ± 7.5 ms (mean ± SD). Analysis of the visual spectral sensitivity of dark-adapted specimens indicated that the sensitivity maximum was centered at a wavelength of 563 nm in the yellow–green region of the spectrum. The critical flicker fusion frequency increased as stimulus irradiance increased, up to a maximum of 44.3 Hz at almost the same stimulus irradiance of the K value.