AUTHOR=Appudurai Audrey M. , Hart Nathan S. , Zurr Ionat , Collin Shaun P. 

TITLE=Morphology, Characterization and Distribution of Retinal Photoreceptors in the South American (Lepidosiren paradoxa) and Spotted African (Protopterus dolloi) Lungfishes

JOURNAL=Frontiers in Ecology and Evolution

VOLUME=4

YEAR=2016

URL=https://www.frontiersin.org/journals/ecology-and-evolution/articles/10.3389/fevo.2016.00078

DOI=10.3389/fevo.2016.00078

ISSN=2296-701X

ABSTRACT=<p>Lungfishes are the closest living relatives of the ancestors to all terrestrial vertebrates and have remained relatively unchanged since the early Lochkovin period (410 mya). Lungfishes, therefore, represent a critical stage in vertebrate evolution and their sensory neurobiology is of considerable interest. This study examines the ultrastructure of the retina of two species of lungfishes: the South American lungfish, <italic>Lepidosiren paradoxa</italic> and the spotted African lungfish, <italic>Protopterus dolloi</italic> in an attempt to assess variations in photoreception in these two ancient groups of sarcopterygian (lobe-finned) fishes. In juvenile <italic>P. dolloi</italic>, the retina contains one rod and two cone photoreceptor types (one containing a red oil droplet), while only one rod and one cone photoreceptor type is present in adult <italic>L. paradoxa</italic>. Both species lack double cones. The large size and inclusion of oil droplets in both species apart from one of the cone photoreceptor types in <italic>P. dolloi</italic> suggests that <italic>L. paradoxa</italic> and <italic>P. dolloi</italic> are adapted for increasing sensitivity. However, the complement of photoreceptor types suggests that there may be a major difference in the capacity to discriminate color (dichromatic and monochromatic photoreception in <italic>P. dolloi</italic> and <italic>L. paradoxa</italic>, respectively). This study suggests that the visual needs of these two species may differ.</p>