Petrocephalus of Odzala offer insights into evolutionary patterns of signal diversification in the Mormyridae, a family of weakly electrogenic fishes from Africa

Publication Type:Journal Article
Year of Publication:2008
Authors:Lavoué, S., Arnegard, M. E., Sullivan, J. P., Hopkins C. D.
Journal:Journal of Physiology-Paris
Volume:102
Pagination:322-339
Date Published:Jul-Nov
ISBN Number:0928-4257
Keywords:adaptive radiation, communication signals, electric organ anatomy, electric organ discharge, electrosensory modality, food-habits, gnathonemus-petersii mormyridae, molecular evolution, petrocephalus, pollimyrus-isidori, riverine species flock, sexual signal evolution, sexual-dimorphism, species marker, type npp electrocytes, wave-forms
Abstract:

Electric signals of mormyrid fishes have recently been described from several regions of Africa. Members of the Mormyridae produce weak electric organ discharges (EODs) as part of a specialized electrosensory Communication and orientation system. Sympatric species often express distinctive EODs, which may contribute to species recognition during mate choice in some lineages. Striking examples of interspecific EOD variation within assemblages have been reported for two monophyletic radiations: the Paramormyrops of Gabon and the Campylomormyrus of Lower Congo. Here, we describe a speciose assemblage of Petrocephalus in the Lekoli River system of Odzala National Park, Republic of Congo. This widespread genus comprises the Subfamily (Petrocephalinae) that is the Sister group to all other mormyrids (Mormyrinae). Eleven Petrocephalus species were collected in Odzala, five of which are not described taxonomically. We quantify EOD variation within this assemblage and show that all eleven species produce EOD waveforms of brief duration (species means range from 144 to 663 mu s) compared to many other mormyrids. We also present reconstructed phylogenetic relationships among species based on cytochrome b sequences. Discovery of the Odzala assemblage greatly increases the number of Petrocephalus species for which EODs and DNA sequence data are available, permitting a first qualitative comparison between mormyrid Subfamilies of the divergence patterns that have been described within lineages. We find that the Petrocephalus assemblage in Odzala is not a monophyletic radiation. Genetic divergence among Petrocephalus species often appears higher than among Paramormyrops or Campylomormyrus species. In contrast, results of this study and others Suggest that Petrocephalus may generally exhibit less interspecific EOD divergence, as well as smaller sex differences in EOD waveforms, compared to Paramormyrops and Campylomormyrus. We discuss possible causes and consequences of EOD diversification patterns observed within mormyrid subfamilies as a framework for future comparative studies of signal evolution using this emerging model system. (c) 2008 Elsevier Ltd. All rights reserved.

URL: https://doi.org/10.1016/j.jphysparis.2008.10.003
DOI:10.1016/j.jphysparis.2008.10.003
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