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Background Teleost fishes comprise more than half of the vertebrate species. Within teleosts, most phylogenies consider the split between Osteoglossomorpha and Euteleosteomorpha/Otomorpha as basal, preceded only by the derivation of the most primitive group of teleosts, the Elopomorpha. While Osteoglossomorpha are generally species poor, the taxon contains the African weakly electric fish (Mormyroidei), which have radiated into numerous species. Within the mormyrids, the genus Campylomormyrus is mostly endemic to the Congo Basin. Campylomormyrus serves as a model to understand mechanisms of adaptive radiation and ecological speciation, especially with regard to its highly diverse species-specific electric organ discharges (EOD). Currently, there are few well-annotated genomes available for electric fish in general and mormyrids in particular. Our study aims at producing a high quality genome and to use this to examine genome evolution in relation to other teleosts. This will facilitate further understanding of the evolution of the osteoglossomorpha fish in general and of electric fish in particular. Results A high quality weakly electric fish (C. compressirostris) genome was produced from a single individual with a genome size of 862Mb, consisting of 1,497 contigs with an N50 of 1,399 kb and a GC-content of 43.69%. Gene predictions identified 34,492 protein-coding genes, which is a higher number than in the two other available Osteoglossomorpha genomes of Paramormyrops kingsleyae and Scleropages formosus. A CAFE5 analysis of gene family evolution comparing 33 teleost fish genomes suggests an overall faster gene family turnover rate in Osteoglossomorpha than in Otomorpha and Euteleosteomorpha. Moreover, the ratios of expanded/contracted gene family numbers in Osteoglossomorpha are significantly higher than in the other two taxa, except for species that had undergone an additional genome duplication (Cyprinus carpio and Oncorhynchus mykiss). As potassium channel proteins are hypothesized to play a key role in EOD diversity among species, we put a special focus on them, and manually curated 16 Kv1 genes. We identified a tandem duplication in the KCNA7a gene in the genome of C. compressirostris. Conclusions We present the fourth genome of an electric fish and the third well-annotated genome for Osteoglossomorpha, enabling us to compare gene family evolution among major teleost lineages. Osteoglossomorpha appear to exhibit rapid gene family evolutiona, with more gene family expansions than contractions. The curated Kv1 gene family showed seven gene clusters, which is more than in other analyzed fish genomes outside Osteoglossomorpha. The KCNA7a, encoding for a potassium channel central for EOD production and modulation, is tandemly duplicated which may related to the diverse EOD observed among Campylomormyrus species.

Coevolution is often considered a major driver of speciation, but evidence for this claim is not always found because diversity might be cryptic. When morphological divergence is low, molecular data are needed to uncover diversity. A taxon for which this holds true are the mites, which are known for their extensive and often cryptic diversity. We studied mites of the genus Poecilochirus that are phoretic on burying beetles (Silphidae: Nicrophorus). Poecilochirus taxonomy is poorly understood. Most studies on this genus focus on the evolutionary ecology of Poecilochirus carabi sensu lato, a complex of at least two biological species. Based on molecular data of 230 specimens from 43 locations worldwide, we identified 24 genetic clusters that may represent species. We estimate that these mites began to diversify during the Paleogene, when the clade containing P. subterraneus branched off and the remaining mites diverged into two further clades. One clade resembles P. monospinosus and P. austroasiaticus. The other clade contains 17 genetic clusters resembling P. carabi s.l.. Among these are P. carabi sensu stricto, P. necrophori, and potentially many additional cryptic species. Our analyses suggest that these clades were formed in the miocene by large-scale geographic separation. Diversification also seems to have happened on a smaller scale, potentially due to adaptation to specific hosts or local abiotic conditions, causing some clusters to specialize on certain beetle species. Our results suggest that biodiversity in this genus was generated by multiple interacting forces shaping the tangled webs of life.

Background: African weakly electric fish generate weakly electric organ discharges (EODs) for orientation and communication. In the mormyrid genus Campylomormyrus, waveform and duration of discharges are species-specific and elongated pulses (> 4ms) are a derived trait. Pulse duration is presumed to depend on electrocyte geometry/excitability or hormonal signaling.Tissue-specific transcriptome analyses across species with different pulse durations have revealed differential expression of genes related to electrocyte excitability. There are also point mutations in ion channel genes which relate to pulse duration. However, a comprehensive assessment of expressed Single Nucleotide Polymorphisms (SNPs) throughout the entire transcriptomes of African weakly electric fish, with the potential to identify further genes influencing EOD duration, is still lacking. This is of particular value, as discharge duration is likely based on multiple cellular mechanisms and various genes. Here, we want to identify non-synonymous SNPs in transcriptomes of Campylomormyrus species differing by EOD duration. Results: We identified 27 candidate genes with inferred positive selection among Campylomormyrus species and at least one non-synonymous substitution specific to Campylomormyrus tshokwe, a species with elongated EODs. Inferred candidate genes had mainly functions linked to transcriptional regulation, cell proliferation, cell differentiation and apoptosis. Further, we identified 27 GO terms and 2 KEGG categories ('Transcription' and 'Cancer: Specific types') for which C. tshokwe (derived elongated EOD) significantly more frequently exhibited a species-specific expressed substitution than C. compressirostris (ancestral short EOD). Conclusion: We performed the first transcriptome-wide SNP analysis among weakly electric fish species (genus Campylomormyrus) and provide putative candidate genes and cellular mechanisms potentially involved in the determination of an elongated discharge in C. tshokwe. Most likely, transcriptional regulation as well cell proliferation, cell differentiation and apoptosis take part in the determination of pulse durations. The processes of cell growth and density are pivotal for tissue morphogenesis and might determine the shape of electric organs. This supports the observed correlation between cell geometry/tissue structure of the electric organ and discharge duration. The inferred expressed SNPs putatively related to EOD duration are a valuable resource for future investigations on this peculiar trait, which may focus on their functional implications.

Karyotyping is a basic method to investigate chromosomal evolution and genomic rearrangements. Sixteen genera within the basal teleost order Osteoglossiformes are currently described cytogenetically. Our study adds information to this chromosomal dataset by determining the karyotype of Campylomormyrus compressirostris, a genus of African weakly electric fish that has not been previously examined. Our results indicate a diploid chromosome number of 2n=48 (4sm+26m+18a) with a fundamental number of FN=72. This chromosome number is identical to the number documented for the sister taxon of the genus Campylomormyrus, i.e., Gnathonemus petersii (2n=48). These results support the close relationship of Campylomormyrus and Gnathonemus. However, the karyotype formula of C. compressirostris is different from Gnathonemus petersii, thereby confirming the high variability of karyotype formulae within the Mormyridae. We infer that the differences in chromosome number and formula of Campylomormyrus relative to other mormyrids may be caused by Robertsonian fusion and pericentric inversion. In addition to the karyotype description and classification of Campylomormyrus, a ChromEvol analysis was used to determine the ancestral haploid chromosome number of osteoglossiform taxa. Our results indicate a relatively conservative haploid chromosome number of n=24 for the most recent common ancestor of Osteoglossiformes and for most of the internal nodes of osteoglossiform phylogeny. Hence, we presume that the high chromosome variability evolved recently on multiple independent occasions. Furthermore, we suggest that the most likely ancestral chromosome number of Mormyridae is either n=24 or n=25. To the best of our knowledge this is the first attempt to determine and classify the karyotype of the weakly electric fish genus Campylomormyrus and to analyze chromosomal evolution within the Osteoglossiformes based on Maximum Likelihood and Bayesian Inference analyses.

African weakly electric fish of the mormyrid genus Campylomormyrus generate pulse-type electric organ discharges (EODs) for orientation and communication. Their pulse durations are species-specific and elongated EODs are a derived trait. So far, differential gene expression among tissue-specific transcriptomes across species with different pulses and point mutations in single ion channel genes indicate a relation of pulse duration and electrocyte geometry/excitability. However, a comprehensive assessment of expressed Single Nucleotide Polymorphisms (SNPs) throughout the entire transcriptome of African weakly electric fish, with the potential to identify further genes influencing EOD duration, is still lacking. This is of particular value, as discharge duration is likely based on multiple cellular mechanisms and various genes. Here we provide the first transcriptome-wide SNP analysis of African weakly electric fish species (genus Campylomormyrus) differing by EOD duration to identify candidate genes and cellular mechanisms potentially involved in the determination of an elongated discharge of C. tshokwe. Non-synonymous substitutions specific to C. tshokwe were found in 27 candidate genes with inferred positive selection among Campylomormyrus species. These candidate genes had mainly functions linked to transcriptional regulation, cell proliferation and cell differentiation. Further, by comparing gene annotations between C. compressirostris (ancestral short EOD) and C. tshokwe (derived elongated EOD), we identified 27 GO terms and 2 KEGG pathway categories for which C. tshokwe significantly more frequently exhibited a species-specific expressed substitution than C. compressirostris. The results indicate that transcriptional regulation as well cell proliferation and differentiation take part in the determination of elongated pulse durations in C. tshokwe. Those cellular processes are pivotal for tissue morphogenesis and might determine the shape of electric organs supporting the observed correlation between electrocyte geometry/tissue structure and discharge duration. The inferred expressed SNPs and their functional implications are a valuable resource for future investigations on EOD durations.

Made available in DSpace on 2018-12-11T17:08:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-02-29 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Deutsche Forschungsgemeinschaft Animal-associated microbial communities can play major roles in the physiology, development, ecology, and evolution of their hosts, but the study of their diversity has yet focused on a limited number of host species. In this study, we used high-throughput sequencing of partial sequences of the bacterial 16S rRNA gene to assess the diversity of the gutinhabiting bacterial communities of 212 specimens of tropical anuran amphibians from Brazil and Madagascar. The core gut-associated bacterial communities among tadpoles from two different continents strongly overlapped, with eight highly represented operational taxonomic units (OTUs) in common. In contrast, the core communities of adults and tadpoles from Brazil were less similar with only one shared OTU. This suggests a community turnover at metamorphosis. Bacterial diversity was higher in tadpoles compared to adults. Distinct differences in composition and diversity occurred among gut bacterial communities of conspecific tadpoles from different water bodies and after experimental fasting for 8 days, demonstrating the influence of both environmental factors and food on the community structure. Communities from syntopic tadpoles clustered by host species both in Madagascar and Brazil, and the Malagasy tadpoles also had species-specific isotope signatures. We recommend future studies to analyze the turnover of anuran gut bacterial communities at metamorphosis, compare the tadpole core communities with those of other aquatic organisms, and assess the possible function of the gut microbiota as a reservoir for protective bacteria on the amphibian skin. Zoological Institute Technische Universit�t Braunschweig, Mendelssohnstr. 4 Departamento de Zoologia Instituto de Bioci�ncias UNESP-Univ Estadual Paulista Campus Rio Claro, Av 24A, N 1515 Department of Ecology and Evolutionary Biology University of Colorado, Ramaley N-122, UCB 334 Evolutionary Biology and Special Zoology Institute for Biochemistry and Biology University of Potsdam, Karl-Liebknecht-Str. 24-25 Visualization Group Otto-von-Guericke University D�partement de Biologie Animale Universit� d’Antananarivo, 101 Antananarivo Museum f�r Naturkunde Leibniz-Institut f�r Evolutions-und Biodiversit�tsforschung, Invalidenstrasse 43 Department of Genome Analytics Helmholtz Centre for Infection Research Th�nen Institute of Biodiversity, Bundesallee 50 Department of Animal Ecology and Conservation University of Hamburg, Martin-Luther-King Platz 3 Departamento de Zoologia Instituto de Bioci�ncias UNESP-Univ Estadual Paulista Campus Rio Claro, Av 24A, N 1515 CAPES: 88881.062205/2014-01 Deutsche Forschungsgemeinschaft: GL 665/1-1 Deutsche Forschungsgemeinschaft: VE247/2-1 Deutsche Forschungsgemeinschaft: VE247/9-1