@article {582, title = {Female choice by electric pulse duration: attractiveness of the males{\textquoteright} communication signal assessed by female bulldog fish, Marcusenius pongolensis (Mormyridae, Teleostei)}, journal = {Journal of Experimental Biology}, volume = {211}, year = {2008}, month = {Mar-06-2009}, pages = {1969 - 1977}, abstract = {

In adult males of the South African weakly electric bulldog fish, Marcusenius pongolensis, the duration of the electric organ discharge (EOD) increases with body size over lifetime. Although there is experimental support for intrasexual selection (male\–male competition) having shaped the males\&$\#$39; EOD pulse duration in evolution, nothing is known about intersexual selection, such as female choice. Playback of 25 natural male EODs of pulse duration varying from 320 \μs (close to the average female value) to 716\μ s, to eight female experimental subjects elicited approach, head butts and circling behaviour. The rate of head butts on the dipole electrode model increased significantly with stimulus pulse duration in seven out of eight experimental subjects. In ten experimental female subjects we contrasted the shortest playback pulse with simultaneous playback of one of four longer ones (424, 524, 628 and 716 \μs). Pooled responses for all experimental subjects were stronger for the dipole playing back the longer pulse in a pulse pair. The difference in the number of head butts (\Δhead butts) that were dealt the two dipoles per 60 s test session increased significantly with the difference in pulse duration (\Δpulse duration). The increase followed a significant linear trend (P\<0.0001). Similar results were obtained for \Δassociation time, \Δcircles with head butts, and\Δ circles without head butts. These results suggest that a male\&$\#$39;s reproductive success is enhanced by longer, i.e. more attractive EODs, and that both intra- and intersexual selection must have played a significant role in shaping the EOD of male M. pongolensis.

}, issn = {0022-0949}, doi = {10.1242/jeb.016949}, url = {http://jeb.biologists.org/cgi/doi/10.1242/jeb.016949https://syndication.highwire.org/content/doi/10.1242/jeb.016949}, author = {Machnik, P. and Bernd Kramer} } @article {409, title = {Petrocephalus of Odzala offer insights into evolutionary patterns of signal diversification in the Mormyridae, a family of weakly electrogenic fishes from Africa}, journal = {Journal of Physiology-Paris}, volume = {102}, number = {4-6}, year = {2008}, note = {411CHTimes Cited:3Cited References Count:84}, month = {Jul-Nov}, pages = {322-339}, 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.

}, 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}, isbn = {0928-4257}, doi = {10.1016/j.jphysparis.2008.10.003}, url = { https://doi.org/10.1016/j.jphysparis.2008.10.003}, author = {S{\'e}bastien Lavou{\'e} and Matthew E Arnegard and John P Sullivan and Carl D Hopkins} } @article {410, title = {Differentiation of morphology, genetics and electric signals in a region of sympatry between sister species of African electric fish (Mormyridae)}, journal = {Journal of Evolutionary Biology}, volume = {21}, number = {4}, year = {2008}, note = {312QYTimes Cited:5Cited References Count:70}, month = {Jul}, pages = {1030-1045}, abstract = {

Mormyrid fishes produce and sense weak electric organ discharges (EODs) for object detection and communication, and they have been increasingly recognized as useful model organisms for studying signal evolution and speciation. EOD waveform variation can provide important clues to sympatric species boundaries between otherwise similar or morphologically cryptic forms. Endemic to the watersheds of Gabon (Central Africa), Ivindomyrus marchei and Ivindomyrus opdenboschi are morphologically similar to one another. Using morphometric, electrophysiological and molecular characters [cytochrome b sequences and amplified fragment length polymorphism (AFLP) genotypes], we investigated to what extent these nominal mormyrid species have diverged into biological species. Our sampling covered the known distribution of each species with a focus on the Ivindo River, where the two taxa co-occur. An overall pattern of congruence among datasets suggests that I. opdenboschi and I. marchei are mostly distinct. Electric signal analysis showed that EODs of I. opdenboschi tend to have a smaller initial head-positive peak than those of I. marchei, and they often possess a small third waveform peak that is typically absent in EODs of I. marchei. Analysis of sympatric I. opdenboschi and I. marchei populations revealed slight, but significant, genetic partitioning between populations based on AFLP data (F-ST approximate to 0.04). Taken separately, however, none of the characters we evaluated allowed us to discriminate two completely distinct or monophyletic groups. Lack of robust separation on the basis of any single character set may be a consequence of incomplete lineage sorting due to recent ancestry and/or introgressive hybridization. Incongruence between genetic datasets in one individual, which exhibited a mitochondrial haplotype characteristic of I. marchei but nevertheless fell within a genetic cluster of I. opdenboschi based on AFLP genotypes, suggests that a low level of recent hybridization may also be contributing to patterns of character variation in sympatry. Nevertheless, despite less than perfect separability based on any one dataset and inconclusive evidence for complete reproductive isolation between them in the Ivindo River, we find sufficient evidence to support the existence of two distinctive species, I. opdenboschi and I. marchei, even if not \’biological species\’ in the Mayrian sense.

}, keywords = {adaptive radiation, aflp, electric fish, electric organ discharge, gnathonemus-petersii mormyridae, introgression, markers, mitochondrial-DNA, mormyroidea, phylogeny, population-structure, reproductive isolation, speciation, teleostei}, isbn = {1010-061X}, url = {://000256687100010}, author = {S{\'e}bastien Lavou{\'e} and John P Sullivan and Matthew E Arnegard and Carl D Hopkins} } @article {890, title = {Adaptive radiation in the Congo River: An ecological speciation scenario for African weakly electric fish (Teleostei; Mormyridae; Campylomormyrus)}, journal = {Journal of Physiology-Paris}, volume = {102}, year = {2008}, month = {7/2008}, pages = {340 - 346}, abstract = {

he ultimate aim of this study is to better understand the diversification of African weakly electric fish in the Congo River. Based on a robust phylogenetic hypothesis we examined the radiation within the mor- myrid genus Campylomormyrus. Morphological traits relevant for the divergence between the identified species were detected. Among them, the variation in the shape of the trunk-like elongated snout sug- gested the presence of different trophic specializations. Furthermore, the chosen model taxon, the genus Campylomormyrus, exhibits a wide diversity of electric organ discharge (EOD) waveforms. A comparison of EOD waveform types and phylogenetic relationships showed major differences in EOD between closely related species. This indicates that the EOD might function as a reproductive isolation mechanism. In con- clusion, we provide a plausible scenario of an adaptive radiation triggered by sexual selection and assor- tative mating based on EOD characteristics, but caused by a divergent selection on the feeding apparatus. These findings point towards an adaptive radiation of at least some Campylomormyrus species occurring in the Lower Congo River.

}, issn = {09284257}, doi = {10.1016/j.jphysparis.2008.10.002}, author = {Philine G.D. Feulner and Frank Kirschbaum and Ralph Tiedemann} } @article {354, title = {Effect of conductivity changes on the stability of electric signal waveforms in dwarf stonebashers (Mormyridae; Pollimyrus castelnaui, P. marianne)}, journal = {Journal of Comparative Physiology A}, volume = {194}, year = {2008}, month = {10/2008}, pages = {915 - 919}, issn = {1432-1351}, doi = {10.1007/s00359-008-0360-0}, author = {Baier, Bernd} }