Mitochondrial genomes and phylogenetic analysis of Central American weakly-electric fishes:Apteronotus rostratus, Brachyhypopomus occidentalisandSternopygus dariensis

Abstract

21Electric fishes are a diverse group of freshwater organisms with the ability to generate 22 electric organ discharges (EODs) that are used for communication and electrolocation. Over 23 200 species have originated in South America, but of these, only a few have managed to 24 colonize the Central American Isthmus. Here, we assembled two complete and one nearly 25 complete mitochondrial genomes (mitogenomes) for three Central American Gymnotiformes: 26Sternopygus dariensis, Brachyhypopomus occidentalis and Apteronotus rostratus. We then 27 explored the three species' phylogenetic position in the context of South American electric 28 fishes. Mitogenomes were organized in the standard fish mitogenome order, and presented 29 sizes of 16,600, 16,540 and 15,940 base pairs (bp) (nearly complete) for S. dariensis, B. 30 occidentalis and A. rostratus, respectively. We uncovered a novel 60 bp intergenic spacer 31 (IGS) located between the COII and tRNA Lys genes, which appears to be unique to the 32Apteronotidae. Furthermore, phylogenetic relationships supported the traditional monophyly 33 of Gymnotiformes, with the three species positioned within their respective family. In 34 addition, the genus Apteronotus was placed as the basal taxon of the order. Finally, we found 35 high sequence divergence (13.3%) between our B. occidentalis specimen and a sequence 36 previously reported in GenBank, suggesting that the prior mitogenome of B. occidentalis 37 represents a different South American species that was misidentified. Indeed, phylogenetic 38 analyses using Cytochrome b gene across the genus placed the previously reported individual 39 within B. bennetti. Our study provides novel mitogenome resources that will advance our 40 understanding of the diversity and phylogenetic history of Neotropical fishes. 41 42

Comparative Analysis of Complete Mitochondrial Genomes of Three Gerres Fishes (Perciformes: Gerreidae) and Primary Exploration of Their Evolution History

“…Gene overlap was one reason for mitochondrial genome compact, and the smaller mitochondrial genomes pass to offspring more frequently than the larger ones [40]. However, selection was responsible for genomes size variation, relating to adapt new environment [38,40]. The same overlapping regions were detected in the Gerres species, indicating they might have their own mechanism to cope with the environment.…”

“…The O L was always found in the intergenic region between two conserved genes [36], and the three mitogenomes were discovered. The O L was usually observed between tRNA-Asn and tRNA-Cys in bony fishes, and the secondary structure that is folded into a stable stem-loop was the main feature of O L [37,38].…”

Comparative Mitogenome Characterization of Cryptic Asian Seabass (Lates calcarifer) in Captivity within Peninsular Malaysia

“…Mitochondrial genome compact could occur due to the gene overlap and genome info often passed down to offspring by the smaller mitochondrial [53]. But genome size variation selection always involved the adaptation ability to the new location [54]. The Lates sp.…”