Document Detail

Morphology, characterization, and distribution of retinal photoreceptors in the Australian lungfish Neoceratodus forsteri (Krefft, 1870).
MedLine Citation:
PMID:  16320259     Owner:  NLM     Status:  MEDLINE    
The Australian lungfish Neoceratodus forsteri (Dipnoi) is an ancient fish that has a unique phylogenetic relationship among the basal Sarcopterygii. Here we examine the ultrastructure, histochemistry, and distribution of the retinal photoreceptors using a combination of light and electron microscopy in order to determine the characteristics of the photoreceptor layer in this living fossil. Similar proportions of rods (53%) and cones (47%) reveal that N. forsteri optimizes both scotopic and photopic sensitivity according to its visual demands. Scotopic sensitivity is optimized by a tapetum lucidum and extremely large rods (18.62 +/- 2.68 microm ellipsoid diameter). Photopic sensitivity is optimized with a theoretical spatial resolving power of 3.28 +/- 0.66 cycles degree(-1), which is based on the spacing of at least three different cone types: a red cone containing a red oil droplet, a yellow cone containing a yellow ellipsoidal pigment, and a colorless cone containing multiple clear oil droplets. Topographic analysis reveals a heterogeneous distribution of all photoreceptor types, with peak cone densities predominantly found in temporal retina (6,020 rods mm(-2), 4,670 red cones mm(-2), 900 yellow cones mm(-2), and 320 colorless cones mm(-2)), but ontogenetic changes in distribution are revealed. Spatial resolving power and the diameter of all photoreceptor types (except yellow cones) increases linearly with growth. The presence of at least three morphological types of cones provides the potential for color vision, which could play a role in the clearer waters of its freshwater environment.
Helena J Bailes; Stephen R Robinson; Ann E O Trezise; Shaun P Collin
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The Journal of comparative neurology     Volume:  494     ISSN:  0021-9967     ISO Abbreviation:  J. Comp. Neurol.     Publication Date:  2006 Jan 
Date Detail:
Created Date:  2005-12-06     Completed Date:  2006-02-06     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  0406041     Medline TA:  J Comp Neurol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  381-97     Citation Subset:  IM    
Copyright Information:
Copyright 2005 Wiley-Liss, Inc
School of Biomedical Sciences, The University of Queensland, St. Lucia, Brisbane, Queensland 4072, Australia.
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MeSH Terms
Cell Count
Choroid / cytology,  ultrastructure
Color Perception / physiology
Fishes / anatomy & histology*,  physiology
Oils / analysis
Retina / cytology*,  physiology,  ultrastructure
Retinal Cone Photoreceptor Cells / chemistry,  cytology,  ultrastructure*
Retinal Pigments / chemistry,  classification*
Retinal Rod Photoreceptor Cells / chemistry,  cytology,  ultrastructure*
Reg. No./Substance:
0/Oils; 0/Retinal Pigments

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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