The role of nonapeptides in electrocommunication behaviour in gymnotiform weakly electric fish By Ali Mokdad Department of Biology McGill University, Montreal August 2016 A thesis submitted to McGill University in partial fulfillment of the requirements of the degree of Master of Science in Biology. © Ali Mokdad 2016 1 Table of Contents Table of Contents Abstract ....................................................................................................................................1 Résumé .......................................................................................................................................................3 Acknowledgments ................................................. and Contribution.......................................................................................................5 General Introduction ...........................................................................................7 Review - The role of nonapeptides ................................................. in social ...................................................communication: A case........................8 for gymnotiform weakly electric fish Introduction ................................................................................................................................11 Nonapeptide .................................................systems in teleost fish ...............................................................................11 Communication behaviour ..............................................................................13 Vocal communication behaviour .................................................................................................18 Electrocommunication behaviour .............................................................................18 Segregated neural pathways control ................................................. electrocommunication behaviour..........................20 ......... Connections between the electromotor system and POA-AH 22 Nonapeptide effects on electrocommunication behaviou r.............................25 Nonapeptides and wave-type fish .........................28 Nonapeptides and pulse-type fish .....................................................................28 Conclusion .......................................................................31 Investigating the roles ................................................. of isotocin in electrocommuni...................................................cation behaviour...............................37 in a weakly electric fish, Apteronotus leptorhynchus Introduction ....................................................................................40 Nonapeptide ................................................. systems and social behaviour...............................................................................40 ........................................................40 2 Nonapeptides and descending motor pathways in teleosts Electrocommunication behaviour ..........................41 Nonapeptide control of electromotor .................................................. circuits ............................42 Goal ......................................................44 Materials .................................................. and Methods ..........................................................................................46 Animal care and housing ...........................................................................................................46 Recording and stimulation ................................................................................................46 Experimental design ............................................................................................47 Chirp assay .........................................................................................................48 Chirp and JAR .................................................. analysis .....................................................................48 Statistical analysis ...................................................................................................49 Results .............................................................................................................50 Effect .................................................. of isotocin on baseline................................................... EODf ........................................50 Effect of isotocin on JAR excursion .............................................................................50 Chirp analysis ..............................................................................51 Effect of isotocin .................................................. on type-I and type-II chirp................................................... production ...................51 Discussion ..................................52 Summary and Final .................................................. Conclusion ...................................................................................53 Figures and Tables .......................................................................................................57 References ..................................................................................................................................60 ...................................................................................................................................................75 3 Abstract The nonapeptide hormones, arginine vasotocin (AVT) and isotocin (IT), play important roles in mediating a wide range of social behaviour in fish. Gymnotiform weakly electric fish use their electric organ discharge (EOD) to produce an expansive array of social electric signals. These behaviours share relatively simple neural elements by which they are controlled. The first section of this thesis reviews the current literature pertaining to nonapeptide influence on electrocommunication behaviour. AVT has been shown to modulate various electrocommunication behaviours by influencing segregated neural pathways controlling distinct electric displays. In pulse-type weakly electric fish, AVT modulates nocturnal increases in EOD frequency (EODf). Among these same fish, AVT also had an effect on EOD rate changes signalling submission and dominance. In wave-type fish, AVT modulates the production of two types of “chirps” – transient increases in EOD used as courtship or aggressive signals. AVT decreased the production of aggressive signals and increased the production of courtship signals. AVT also increased the magnitude of the jamming avoidance response (JAR), the communicative function of which is still poorly understood. The second section ofApteronotus this thesis was leptorhynchus aimed at investigating the effects of IT on three electric behaviours in male , a South American wave-type electric fish: baseline EOD, the JAR, and chirping behaviour. Intramuscular injection of IT showed no statistically significant effect on any of the three behaviours. The lack of a response to IT was somewhat surprising since the behavioural functions of AVT and IT systems are related. A number of reasons are discussed that may explain the lack of response, chief among them being the possibility that receptor expression was low in the 4 fish tested. Further exploration of IT and AVT in relation to communication is warranted and weakly electric fish are a particularly advantageous system in this regard. 5 Résumé Les hormones nonapeptidiques, arginine vasotocine (AVT) et isotocine (IT), jouent un rôle dans la médiation d’un grand nombre de comportements sociaux chez les poissons. Les poissons faiblement électriques gymnotiformes utilisent leur décharge de l’organe électrique (EOD) pour produire un éventail extensif de signaux électriques sociaux. Ces comportements partagent des éléments neuronaux simples qui les contrôlent. La première section de cette thèse examine la littérature actuelle pertinente à l’influence des nonapeptides sur le comportement électro-communicatif. L’AVT module plusieurs comportements électro-communicatifs, et ceci par l’influence de réseaux neuraux séparés qui contrôlent des signaux électriques distincts. Chez les poissons faiblement électriques de type pulsatif, l’AVT module les augmentations nocturnes de la fréquence des décharges de l’organe électrique (EODf). Chez ces mêmes poissons, l’AVT a aussi un effet sur le taux de changement des signaux de soumission ou de dominance émis par l’EOD. Chez les poissons à décharge par ondes, l’AVT module la production de deux types de « pépiement » - des augmentations transitoires de l’EOD utilisées tels des signaux d’agression ou de cour. L’AVT a diminué la production de signaux d’agression, et augmenté le taux de signaux de cour émis. L’AVT a aussi augmenté l’intensité des réponses d’évitements du brouillage (JAR), dont la fonction communicative n’est pas encore assez analysée. La deuxième section de cette thèse vise à étudier les effets de l’isotocine (IT) sur trois comportements électriques chez les Apteronotus Ieptorhunchus mâles, un poisson à décharge électrique ondulée Sud- Américain; ces comportements étant l’EOD de base, la JAR, et les pépiements. Des injections intramusculaires d’IT ne montrent aucun effet sur ces trois comportements. L’absence de réaction à l’injection d’IT est surprenante puisque les fonctions comportementales des 6 systèmes d’AVT et d’IT sont fonctionnellement liés. Un nombre de raisons sont analysées