Amazon Nights II: Electric Boogaloo-Neural Adaptations for Communication in Three Species of Weakly Electric FIsh

Abstract

Amazon Nights II: Electric Boogaloo Neural adaptations for communication in three species of weakly electric fish Kathryne Allen Sensory systems are the tools by which organisms collect information about the environment. The environments that these systems have evolved to function within shape how they accomplish this task, as each has its own challenges in regards to noise and physical limits of transmission media. In this dissertation, I examine how a unique sensory system, the electrosensory system of three species of weakly electric fishes, is adapted to accomplish the specific task of detecting and accurately encoding conspecific communication. Communication is useful lens for studying how salient signals are filtered from confounding noise and how coding strategies are adapted across species. I specifically show that the physical structure of a signal can dictate how it is encoded by the sensory system, and further demonstrate that different coding strategies are correlated with different perceptual abilities. I then examine how the behavioral use and ethological significance of communication signals also changes which coding strategies are used to encode those signals. Finally, I show that the social context in which signals are received can influence which coding strategies are adopted. The list of people I have to thank is long, and no matter whom I mention, I am sure this page will fall short of comprehensive. First, I want to credit all the amazing instructors I have had. Every single one of you have taught me the joy in hard work, curiosity, and to trust in my own abilities. In particular, I need to thank Drs. Ann Fabirkiewicz, Doug Shedd, and Kristin Bliss. You all shaped my undergrad experience and each contributed to my perspectives on both science and life. I especially need to thank Dr. Kurt Siedman. You were exactly the research advisor I needed, if not the one I wanted. I am forever grateful that you chose to herd this cat. Next, I need to acknowledge my family. The advantage to having a giant, Brady Bunch, mess of a family is that there is always someone who gets it, no matter what "it" is. Micki, Missa, Mere, Jennifer, and Don, thanks for all the wisdom, much of it extremely hard earned. Gene, thank you for being gentle and steadfast. Cathy, thank you for the levity. Dad, thank you for being consistently encouraging. Mom, thank you for literally everything. Thank you to all of the friends who have brought me joy, perspective, and support through everything.

Discrimination and behavioral responses to communication signals compared across Apteronotids.

“…Therefore, our experiments demonstrate that there is a difference in how relevant the information is to the behavior even though we cannot claim that the difference originated from a perceptual difference. Furthermore, our conclusions are also supported by differences in sensory coding (Allen andMarsat, 2018, 2019;Allen, 2019) that also suggest that different amount of information reaches the higher brain areas. Together, the neurophysiological data previously published (Marsat and Maler, 2010) and the behavioral results presented here clearly reveal qualitative differences in discrimination of chirps.…”

“…This large and species-rich family displays countless variations in size, body morphology, sexual dimorphism, and communication signals (Alves-Gomes et al, 1995;Compton and Albert, 2006;Turner et al, 2007). Due to a rich existing literature detailing the sensory mechanisms and the behaviors in these fish, they are a powerful model system in neuroscience and the cross-species variability makes it a good target for comparative studies (Allen andMarsat, 2018, 2019;Tallarovic & Zakon, 2005;Turner et al, 2007). We know that the basic tuning properties of electroreceptors match the frequency of the species-specific signals across ghost knifefish (Hopkins, 1976).…”

“…Low-frequency beats are typical of same-sex aggressive interactions. Alternatively, chirps elicit graded heterogeneous responses allowing both detection and discrimination of the chirps when occurring on a high frequency beat (Allen andMarsat, 2018, 2019). Chirps on high frequency beats are typical of male-female interactions and occur during courtship.…”

“…Being the most social and possessing the most complex chirps (often multi-peaked) it was thought to have the potential of displaying the highest level of discrimination. In a recent study (Allen, 2019) it was found that much like A. albifrons, A. devenanzii encoded chirps through graded, heterogeneous firing across PCs, with increased firing that corresponded with the FM and accompanied by the inversely correlated AM of the chirp. However, chirp coding was more accurate than for A. albifrons.…”

“…A. devenanzii were also tested neurophysiologically to determine their coding accuracy for chirp stimuli (Allen, 2019). The ELL responses accurately encoded the chirp's structure in graded population responses for all beat frequencies.…”