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Title: The evolution and functional morphology of hemipteran vibrational organs
Author: Davranoglou, Leonidas-Romanos
ISNI:       0000 0004 8507 8666
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2020
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Acoustic and vibrational signals are among the prevalent modes of arthropod communication, exploited by at least 230,000 species (Cocroft and Rodríguez, 2005). Vibroacoustic signals dominate hemipteran communication, being generated by stridulation, wing buzzing, percussion, membrane buckling and shaking of the body relative to the legs (tremulation). The last two mechanisms are produced by basi-abdominal organs known as tymbals in Cicadomorpha and tergal plates in Heteroptera, respectively, whose systematic distribution and homologies are poorly understood. Other groups, such as the planthoppers (Fulgoromorpha) and moss bugs (Coleorrhyncha), are more enigmatic, as they generate vibrations with mechanisms which have so far remained unexplored. In spite of limited available morphological evidence, it has been suggested that all hemipteran basi-abdominal organs are homologous and evolved once (Tymbalia hypothesis) (Wessel et al, 2014). The aim of this dissertation is to elucidate the evolution of hemipteran vibroacoustic organs by describing their biomechanics, morphology and systematic distribution, and to use the resulting data to test the claims of the Tymbalia hypothesis. I used a combination of state-of-the-art methods such as X-ray synchrotron microtomography and confocal laser scanning microscopy with more traditional techniques 10 (e.g. scanning electron microscopy), in order to describe the morphology of vibroacoustic organs from taxa selected from across hemipteran phylogeny. For experiments with living specimens, I used laser Doppler vibrometers to record their vibrational signals and high speed cameras to film the motion of the organs responsible for their production. I find that Fulgoromorpha produce vibrational signals with a novel mechanism I term the "snapping organ", which is biomechanically and morphologically distinct from tymbals. Furthermore, re-examination of supposed stridulatory organs in derbid planthoppers reveals that they are instead more likely to be used in chemical signalling. I show that tymbals are ubiquitous in Cicadomorpha, and that their segmental affinities were misinterpreted by most previous studies. Finally, I document the tergal plate in a systematically important group of Heteroptera, and I challenge the evidence used to support the Tymbalia hypothesis. Overall, this dissertation documents the morphology and systematic distribution of hemipteran vibroacoustic organs in unprecedented detail, and provides a significant step towards resolving their evolutionary origins.
Supervisor: Taylor, Graham ; Mortimer, Beth Sponsor: Elizabeth Hannah Jenkinson Fund
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available