@article {10.1371/journal.pone.0036287, title = {Comparable Ages for the Independent Origins of Electrogenesis in African and South American Weakly Electric Fishes}, journal = {PLoS ONE}, volume = {7}, number = {5}, year = {2012}, month = {05/2012}, pages = {e36287}, abstract = {

One of the most remarkable examples of convergent evolution among vertebrates is illustrated by the independent origins of an active electric sense in South American and African weakly electric fishes, the Gymnotiformes and Mormyroidea, respectively. These groups independently evolved similar complex systems for object localization and communication via the generation and reception of weak electric fields. While good estimates of divergence times are critical to understanding the temporal context for the evolution and diversification of these two groups, their respective ages have been difficult to estimate due to the absence of an informative fossil record, use of strict molecular clock models in previous studies, and/or incomplete taxonomic sampling. Here, we examine the timing of the origins of the Gymnotiformes and the Mormyroidea using complete mitogenome sequences and a parametric Bayesian method for divergence time reconstruction. Under two different fossil-based calibration methods, we estimated similar ages for the independent origins of the Mormyroidea and Gymnotiformes. Our absolute estimates for the origins of these groups either slightly postdate, or just predate, the final separation of Africa and South America by continental drift. The most recent common ancestor of the Mormyroidea and Gymnotiformes was found to be a non-electrogenic basal teleost living more than 85 millions years earlier. For both electric fish lineages, we also estimated similar intervals (16\–19 or 22\–26 million years, depending on calibration method) between the appearance of electroreception and the origin of myogenic electric organs, providing rough upper estimates for the time periods during which these complex electric organs evolved de novo from skeletal muscle precursors. The fact that the Gymnotiformes and Mormyroidea are of similar age enhances the comparative value of the weakly electric fish system for investigating pathways to evolutionary novelty, as well as the influences of key innovations in communication on the process of species radiation.

}, doi = {10.1371/journal.pone.0036287}, url = {http://dx.doi.org/10.1371/journal.pone.0036287}, author = {S{\'e}bastien Lavou{\'e} and Miya, Masaki and Matthew E. Arnegard and John P. Sullivan and Carl D. Hopkins and Nishida, Mutsumi} } @article {836, title = {Differential expression of genes and proteins between electric organ and skeletal muscle in the mormyrid electric fish Brienomyrus brachyistius}, journal = {Journal of Experimental Biology}, volume = {215}, year = {2012}, month = {07/2012}, pages = {2479 - 2494}, abstract = {

Electric organs (EOs) have evolved independently in vertebrates six times from skeletal muscle (SM). The transcriptional changes accompanying this developmental transformation are not presently well understood. Mormyrids and gymnotiforms are two highly convergent groups of weakly electric fish that have independently evolved EOs: while much is known about development and gene expression in gymnotiforms, very little is known about development and gene expression in mormyrids. This lack of data limits prospects for comparative work. We report here on the characterization of 28 differentially expressed genes between SM and EO tissues in the mormyrid Brienomyrus brachyistius, which were identified using suppressive subtractive hybridization (SSH). Forward and reverse SSH was performed on tissue samples of EO and SM resulting in one cDNA library enriched with mRNAs expressed in EO, and a second library representing mRNAs unique to SM. Nineteen expressed sequence tags (ESTs) were identified in EO and nine were identified in SM using BLAST searching of Danio rerio sequences available in NCBI databases. We confirmed differential expression of all 28 ESTs using RT-PCR. In EO, these ESTs represent four classes of proteins: (1) ion pumps, including the - and -subunits of Na+/K+-ATPase, and a plasma membrane Ca2+-ATPase; (2) Ca2+-binding protein S100, several parvalbumin paralogs, calcyclin-binding protein and neurogranin; (3) sarcomeric proteins troponin I, myosin heavy chain and actin-related protein complex subunit 3 (Arcp3); and (4) the transcription factors enhancer of rudimentary homolog (ERH) and myocyte enhancer factor 2A (MEF2A). Immunohistochemistry and western blotting were used to demonstrate the translation of seven proteins (myosin heavy chain, Na+/K+-ATPase, plasma membrane Ca2+-ATPase, MEF2, troponin and parvalbumin) and their cellular localization in EO and SM. Our findings suggest that mormyrids express several paralogs of muscle-specific genes and the proteins they encode in EOs, unlike gymnotiforms, which may post-transcriptionally repress several sarcomeric proteins. In spite of the similarity in the physiology and function of EOs in mormyrids and gymnotiforms, this study indicates that the mechanisms of development in the two groups may be considerably different.

}, issn = {1477-9145}, doi = {10.1242/jeb.063222}, author = {Jason R. Gallant and Carl D. Hopkins and Deitcher, D. L.} } @article {853, title = {Differential expression of genes and proteins between electric organ and skeletal muscle in the mormyrid electric fish Brienomyrus brachyistius}, journal = {Journal of Experimental Biology}, volume = {215}, year = {2012}, month = {07/2012}, pages = {2479 - 2494}, abstract = {

Electric organs (EOs) have evolved independently in vertebrates six times from skeletal muscle (SM). The transcriptional changes accompanying this developmental transformation are not presently well understood. Mormyrids and gymnotiforms are two highly convergent groups of weakly electric fish that have independently evolved EOs: while much is known about development and gene expression in gymnotiforms, very little is known about development and gene expression in mormyrids. This lack of data limits prospects for comparative work. We report here on the characterization of 28 differentially expressed genes between SM and EO tissues in the mormyrid Brienomyrus brachyistius, which were identified using suppressive subtractive hybridization (SSH). Forward and reverse SSH was performed on tissue samples of EO and SM resulting in one cDNA library enriched with mRNAs expressed in EO, and a second library representing mRNAs unique to SM. Nineteen expressed sequence tags (ESTs) were identified in EO and nine were identified in SM using BLAST searching of Danio rerio sequences available in NCBI databases. We confirmed differential expression of all 28 ESTs using RT-PCR. In EO, these ESTs represent four classes of proteins: (1) ion pumps, including the \α- and \β-subunits of Na(+)/K(+)-ATPase, and a plasma membrane Ca(2+)-ATPase; (2) Ca(2+)-binding protein S100, several parvalbumin paralogs, calcyclin-binding protein and neurogranin; (3) sarcomeric proteins troponin I, myosin heavy chain and actin-related protein complex subunit 3 (Arcp3); and (4) the transcription factors enhancer of rudimentary homolog (ERH) and myocyte enhancer factor 2A (MEF2A). Immunohistochemistry and western blotting were used to demonstrate the translation of seven proteins (myosin heavy chain, Na(+)/K(+)-ATPase, plasma membrane Ca(2+)-ATPase, MEF2, troponin and parvalbumin) and their cellular localization in EO and SM. Our findings suggest that mormyrids express several paralogs of muscle-specific genes and the proteins they encode in EOs, unlike gymnotiforms, which may post-transcriptionally repress several sarcomeric proteins. In spite of the similarity in the physiology and function of EOs in mormyrids and gymnotiforms, this study indicates that the mechanisms of development in the two groups may be considerably different.

}, issn = {1477-9145}, doi = {10.1242/jeb.063222}, author = {Jason R. Gallant and Carl D. Hopkins and Deitcher, D. L.} } @article {1823, title = {Petrocephalus Marcusen, 1854 (Osteoglossomorpha: Mormyridae) of the Bangweulu-Mweru ecoregion (Luapula River system, Congo basin), with the description of a new species}, journal = {Journal of Natural History}, volume = {46}, year = {2012}, month = {09/2012}, pages = {2159-2178}, abstract = {A recent collection of African electric fish of the genus Petrocephalus from the Bangweulu-Mweru ecoregion of the Congo basin comprises two endemic species, Petrocephalus squalostoma (Boulenger, 1915), which was previously known only from its type specimens and another specimen, and a new species described herein as Petrocephalus frieli sp. nov. An exclusive set of morphological characters distinguishes P. frieli sp. nov. from P. squalostoma and all other species of Petrocephalus from the Congo basin. Petrocephalus frieli sp. nov. can further be distinguished from the East African Petrocephalus catostoma catostoma (G{\"u}nther, 1866) in having only 12 circumpenduncular scales (versus 15/16 in P. c. catostoma). A molecular phylogenetic analysis confirms the distinctiveness of P. squalostoma and P. frieli sp. nov. among a sampling of 18 species of Petrocephalus. Previous reports of Petrocephalus simus Sauvage, 1879 from the Bangweulu-Mweru ecoregion probably represent misidentifications and the occurrence of P. c. catostoma is not confirmed.}, doi = {10.1080/00222933.2012.708449}, author = {S{\'e}bastien Lavou{\'e}} } @article {1822, title = {A critical revision of the churchill snoutfish, genus Petrocephalus Marcusen, 1854 (Actinopterygii: Teleostei: Mormyridae), from southern and eastern Africa, with the recognition of Petrocephalus tanensis, and the description of five new species}, journal = {Journal of Natural History}, volume = {46}, year = {2012}, month = {09/2012}, pages = {2179{\textendash}2258}, abstract = {

We morphologically and genetically studied the southern African electric fish Petrocephalus catostoma, or churchill, and its six nominal species, five of which by synonymization (three valid subspecies). We reinstate the synonymized species, and recognize Petrocephalus tanensis (Whitehead and Greenwood, 1959) from the Tana River in Kenya, also using electric organ discharges. The Okavango delta (Botswana) is inhabited by Petrocephalus okavangensis sp. nov. and Petrocephalus magnitrunci sp. nov., and the Namibian Cunene River by Petrocephalus magnoculis sp. nov. We recognize Petrocephalus petersi sp. nov. for the Lower Zambezi River (Mozambique), and Petrocephalus longicapitis sp. nov. for the Upper Zambezi River (Namibia). The Lufubu River in Northern Zambia is inhabited by Petrocephalus longianalis sp. nov. For the southern churchill, Petrocephalus wesselsi Kramer and Van der Bank, 2000, we confirm intraspecific and interspecific differentia- tion. Sequence data from mitochondrial DNA confirm differentiation of two new western and two eastern species, forming mutual sister groups.

}, keywords = {allopatric speciation, electric organ discharges, molecular genetics, morphometrics, Systematics}, issn = {ISSN 0022-2933}, doi = {10.1080/00222933.2012.708452}, url = {http://dx.doi.org/10.1080/00222933.2012.708452}, author = {Bernd Kramer and Roger Bills and P. Skelton and Michael Wink} }