Functional foveae in an electrosensory system

• Published in: Journal of comparative neurology (1911) Vol. 511; no. 3; pp. 342 - 359
• Main Authors: Bacelo, Joao, Engelmann, Jacob, Hollmann, Michael, von der Emde, Gerhard, Grant, Kirsty
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 20.11.2008; Wiley
• Subjects: Afferent Pathways; Afferent Pathways - anatomy & histology; Afferent Pathways - physiology; Animal Communication; Animals; Brain; Brain - anatomy & histology; Brain - physiology; Brain Mapping; central magnification; Electric Fish; Electric Fish - anatomy & histology; Electric Fish - physiology; Electric Organ; Electric Organ - anatomy & histology; Electric Organ - physiology; electroreception; fovea; Gnathonemus; Head; Head - anatomy & histology; Life Sciences; mormyrid; mormyromast; Neurons and Cognition; peripheral scaling; Sensory Receptor Cells; Sensory Receptor Cells - physiology
• ISSN: 0021-9967; 1096-9861
• DOI: 10.1002/cne.21843

Several species of Mormyrid weakly electric fish have a mobile chin protuberance that serves as a mobile antenna during prey detection, tracking behaviors, and foraging for food. It has been proposed that it constitutes a fovea of the electrosensory system. The distribution of the three types of receptor organs involved in active imaging of the local surroundings, prey detection, and passive electroreception, and their central projection to the electrosensory lobe (ELL), have been studied in Gnathonemus petersii. Density distributions were compared for different body regions. Primary afferent projections were labeled with biocytin or biotinylated dextrans. This showed that there is considerable central “over‐representation” of the mandibular and nasal regions of the sensory surface involved in electrolocation, at the expense of the other body regions investigated. This over‐representation is not a mere effect of the very high density of receptor organs in these areas, but is found to be due to central magnification. This magnification differs between the subclasses of electroreceptors, suggesting a functional segregation in the brain. We conclude that the chin protuberance and the nasal region are the regions of greatest sensitivity for the resistive, capacitive, and low‐frequency characteristics of the environment, and are probably most important in prey detection, whereas other regions of the skin with a lesser resolution and sensitivity to phase distortion of the EOD, in particular the trunk, are probably designed for imaging larger, inanimate features of the environment. Our data support the hypothesis that the chin appendage and nasal region are functionally distinct electrosensory foveae. J. Comp. Neurol. 511:342–359, 2008. © 2008 Wiley‐Liss, Inc.