@article {572,
	title = {Sensory Specializations of Mormyrid Fish Are Associated with Species Differences in Electric Signal Localization Behavior},
	journal = {Brain, Behavior and Evolution},
	year = {2019},
	month = {Jan-03-2019},
	pages = {1 - 17},
	abstract = {<p>The ability to localize communication signals plays a fundamental role in social interactions. For signal localization to take place, the sensory system of the receiver must extract information about distance and direction to the sender from physical characteristics of the signal. In many sensory systems, information from multiple peripheral receptors must be integrated by central sensory pathways to determine the sender location. Here, we asked whether evolutionary divergence in the electrosensory and visual systems of mormyrid fish is associated with signal localization behavior. In mormyrids, differences in the distribution of electroreceptors on the surface of the skin are associated with differences in the midbrain exterolateral nucleus (EL). Species with electroreceptors clustered in three rosettes on both sides of the head have a small and undifferentiated EL. In contrast, EL is enlarged and subdivided into anterior (ELa) and posterior (ELp) regions in species that have electroreceptors broadly \&shy;distributed throughout the body. Interestingly, species with EL and clustered electroreceptors also have larger visual systems and higher visual acuity than species with ELa/ELp and broadly distributed electroreceptors. Species with broadly distributed electroreceptors and ELa/ELp approached a simulated conspecific by following the curved electric field lines generated by the electrosensory stimulus. In contrast, a species with small EL and clustered electroreceptors, but an enlarged visual system, followed shorter and straighter paths to the stimulus source. In the central electrosensory system, evoked field potentials in response to stimuli delivered from the left versus the right differed more in EL than in ELa/ELp. Our results suggest that signal localization behavior is associated with differences in sensory specializations. We propose that the distribution of electroreceptors on the body affects the ability of individuals to align parallel to electric field lines and maintain such alignment while approaching the signal source. The spatial resolution of sensory information relayed from the periphery to the midbrain in species with clustered electroreceptors may allow for gross, but not fine, processing of sender location. Furthermore, visual information may play an important role in localizing signaling individuals in species with small EL and clustered electroreceptors. In line with previous studies, we suggest that the physiological and behavioral differences associated with signal localization reflect adaptations to different habitats and social environments.</p>
},
	issn = {0006-8977},
	doi = {10.1159/000496493},
	url = {https://www.karger.com/Article/FullText/496493https://www.karger.com/Article/Pdf/496493https://www.karger.com/Article/Pdf/496493},
	author = {V{\'e}lez, Alejandro and Ryoo, Da~Yeon and Bruce A. Carlson}
}
@article {477,
	title = {Independent Evolution of Visual and Electrosensory Specializations in Different Lineages of Mormyrid Electric Fishes},
	journal = {Brain, Behavior and Evolution},
	volume = {82},
	year = {2013},
	month = {Jan-01-2013},
	pages = {185 - 198},
	abstract = {<p>African mormyrid fishes are by far the most diverse group of osteoglossomorph (bony tongue) fishes. Mormyrids communicate using pulses of electricity, and they process electric communication signals in the midbrain exterolateral nucleus (EL). In its ancestral form, the EL is relatively small and homogenous. In two different lineages, however, the EL expanded in size and increased in cytological complexity. This evolutionary change established the perceptual ability to distinguish variation in electric pulse waveform, which plays an important role in species recognition and mate choice. However, the sensory basis of social behavior in species with a small, homogenous EL remains unknown. Using published species descriptions, we found that species in one of these lineages have relatively large eyes. Using sectioned brains, we measured the volume of a major visual region, the optic tectum (OT), and found that this same lineage also has an enlarged OT. We also found that eye size and OT size are highly correlated across species. Phylogenetic analysis suggests that a reduced visual system evolved with the origins of an active electrosense, and that this one particular lineage secondarily evolved an enlarged visual system. Behavioral tests revealed that this enlargement of the visual system established increased visual acuity. Thus, our findings demonstrate that different lineages of mormyrids have evolved visual or electrosensory specializations, but that no lineages have specialized in both. This sensory divergence likely reflects fundamentally different ecologies and suggests that vision may play an especially important role in the social behavior of mormyrids that cannot detect variation in electric signal waveform. Our findings provide an example of evolutionary change in multiple sensory systems among closely related species that lays a foundation for relating ecological adaptation to evolutionary change in multisensory perception and social behavior.</p>
},
	issn = {0006-8977},
	doi = {10.1159/000355369},
	url = {http://www.karger.com?doi=10.1159/000355369},
	author = {Stevens, Jennifer A. and Sukhum, Kimberley V. and Bruce A. Carlson}
}
