QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

First published online January 17, 2007
Journal of Experimental Biology 210, 447-453 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.02658

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Jordão, J. M. Articles by Oliveira, R. F. Search for Related Content PubMed PubMed Citation Articles by Jordão, J. M. Articles by Oliveira, R. F.

Spectral sensitivity of four species of fiddler crabs (Uca pugnax, Uca pugilator, Uca vomeris and Uca tangeri) measured by in situ microspectrophotometry

Joana M. Jordão^1,*, Thomas W. Cronin² and Rui F. Oliveira¹

¹ Unidade de Investigação em Eco-Etologia, ISPA, Rua Jardim do Tabaco, 34, 1149-041 Lisboa, Portugal
² Department of Biological Sciences, University of Maryland Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250 USA

^* Author for correspondence (e-mail: jjordao{at}ispa.pt)

Accepted 21 November 2006

Fiddler crabs have compound eyes that are structurally fairly well understood. However, there has been much debate regarding their spectral sensitivity and capacity to enable colour discrimination. We examined the visual pigments of two North-American species (Uca pugnax and U. pugilator), one species from the Indo-West Pacific (U. vomeris) and the only Eastern-Atlantic species (U. tangeri) of fiddler crabs using in situ microspectrophotometry of frozen sections of dark-adapted eyes. Only one spectral class of visual receptor was found in the larger (R1–7) retinular cells of each species, with maximum absorption peaking between 508 nm and 530 nm (depending upon species). The R8 retinular cell, that might contain a short-wavelength sensitive photopigment and provide a basis for colour vision, was too small to analyze by these methods. Rhabdoms were lined with screening pigment which strongly influenced each species' spectral sensitivity, sharpening the peak and shifting the maximum towards longer wavelengths, on occasion to as far as the 600 nm region. We hypothesize that sensitivity to longer wavelengths enhances contrast between background (blue sky or tall vegetation) and the male major claw during the waving display.

Key words: fiddler crab, spectral sensitivity, microspectrophotometry