Ancient eyes and scorpionflies: Evolution of panorpid visual systems (Mecoptera:Panorpidae)

Scorpionflies (Mecoptera: Panorpidae) are a diverse and ancient group of insects. In fact, the oldest known fossil of an insect capable of metamorphosis is a mecopteran. One feature that distinguishes panorpids from its sister taxa, and also a possible explanation for the groups' longevity, is their visual systems. This highly visual insect employs its vision in courtship, mating, predation, and interspecies combat.  This paper presents the first transcriptome work done in Panorpidae, specifically in the eye. The transcriptome of three panorpid visual systems were obtained. Methods include visual tissue RNA extraction, Roche 454 long sequencing, and bioinformatics tools to assemble and parse the data. The presence of opsins and other phototransduction genes were assessed.  Only long-wavelength opsins were isolated despite extensive effort, a finding that is supported by electrophysiological data. The evolution of the long-wavelength opsin among mecopterans was examined in conjunction with the long-wavelength opsins of close relatives. With these results, we consider potential biological explanations for opsin evolution among this insect lineage.