No abstract

Mitofish is a database of fish mitochondrial genomes (mitogenomes) that includes powerful and precise de novo annotations for mitogenome sequences. Fish occupy an important position in the evolution of vertebrates and the ecology of the hydrosphere, and mitogenomic sequence data have served as a rich source of information for resolving fish phylogenies and identifying new fish species. The importance of a mitogenomic database continues to grow at a rapid pace as massive amounts of mitogenomic data are generated with the advent of new sequencing technologies. A severe bottleneck seems likely to occur with regard to mitogenome annotation because of the overwhelming pace of data accumulation and the intrinsic difficulties in annotating sequences with degenerating transfer RNA structures, divergent start/stop codons of the coding elements, and the overlapping of adjacent elements. To ease this data backlog, we developed an annotation pipeline named MitoAnnotator. MitoAnnotator automatically annotates a fish mitogenome with a high degree of accuracy in approximately 5 min; thus, it is readily applicable to data sets of dozens of sequences. MitoFish also contains re-annotations of previously sequenced fish mitogenomes, enabling researchers to refer to them when they find annotations that are likely to be erroneous or while conducting comparative mitogenomic analyses. For users who need more information on the taxonomy, habitats, phenotypes, or life cycles of fish, MitoFish provides links to related databases. MitoFish and MitoAnnotator are freely available at http://mitofish.aori.u-tokyo.ac.jp/ (last accessed August 28, 2013); all of the data can be batch downloaded, and the annotation pipeline can be used via a web interface.

Uncertainties surrounding the evolutionary origin of the epipelagic fish family Scombridae (tunas and mackerels) are symptomatic of the difficulties in resolving suprafamilial relationships within Percomorpha, a hyperdiverse teleost radiation that contains approximately 17,000 species placed in 13 ill-defined orders and 269 families. Here we find that scombrids share a common ancestry with 14 families based on (i) bioinformatic analyses using partial mitochondrial and nuclear gene sequences from all percomorphs deposited in GenBank (10,733 sequences) and (ii) subsequent mitogenomic analysis based on 57 species from those targeted 15 families and 67 outgroup taxa. Morphological heterogeneity among these 15 families is so extraordinary that they have been placed in six different perciform suborders. However, members of the 15 families are either coastal or oceanic pelagic in their ecology with diverse modes of life, suggesting that they represent a previously undetected adaptive radiation in the pelagic realm. Time-calibrated phylogenies imply that scombrids originated from a deep-ocean ancestor and began to radiate after the end-Cretaceous when large predatory epipelagic fishes were selective victims of the Cretaceous-Paleogene mass extinction. We name this clade of open-ocean fishes containing Scombridae “Pelagia” in reference to the common habitat preference that links the 15 families.

Cooperative breeding has been studied intensively in many species of birds and mammals but remain less well studied in fish. We report a remarkable new example of a cooperatively breeding cichlid from Lake Tanganyika, Neolamprologus obscurus. Using field observations and microsatellite DNA analyses, we studied group structure, helping behavior, relatedness, and dispersal of this species. We present four major observations. First, large territorial breeding males mated with one to eight breeding females, each of which was territorial and unrelated to another. Second, one to ten smaller fish ("subordinates") of both sexes were allowed to stay inside the breeding females' territories. Subordinates were often highly related to both the respective breeding male and female and performed territory defense and shelter maintenance, which is regarded as helping behaviors. Third, one to three subordinate males, similar in size to breeding females, were allowed to stay inside a breeding male's territory but were not tolerated in the breeding females' territories. Pairwise relatedness suggests these individuals are usually sons of the respective breeding male. Fourth, pairwise relatedness estimates suggest that juveniles delay dispersal and assist their mothers in raising offspring. As female subordinates grow up, they leave the father's territory and disperse into other groups. In contrast, male subordinates leave their mother's territory but remain within the territory of their father. The described social system makes N. obscurus a promising new model species to study the evolution of cooperative breeding.

BackgroundA skewed assemblage of two epi-, meso- and bathypelagic fish families makes up the order Myctophiformes – the blackchins Neoscopelidae and the lanternfishes Myctophidae. The six rare neoscopelids show few morphological specializations whereas the divergent myctophids have evolved into about 250 species, of which many show massive abundances and wide distributions. In fact, Myctophidae is by far the most abundant fish family in the world, with plausible estimates of more than half of the oceans combined fish biomass. Myctophids possess a unique communication system of species-specific photophore patterns and traditional intrafamilial classification has been established to reflect arrangements of photophores. Myctophids present the most diverse array of larval body forms found in fishes although this attribute has both corroborated and confounded phylogenetic hypotheses based on adult morphology. No molecular phylogeny is available for Myctophiformes, despite their importance within all ocean trophic cycles, open-ocean speciation and as an important part of neoteleost divergence. This study attempts to resolve major myctophiform phylogenies from both mitogenomic sequences and corroborating evidence in the form of unique mitochondrial gene order rearrangements.ResultsMitogenomic evidence from DNA sequences and unique gene orders are highly congruent concerning phylogenetic resolution on several myctophiform classification levels, corroborating evidence from osteology, larval ontogeny and photophore patterns, although the lack of larval morphological characters within the subfamily Lampanyctinae stands out. Neoscopelidae is resolved as the sister family to myctophids with Solivomer arenidens positioned as a sister taxon to the remaining neoscopelids. The enigmatic Notolychnus valdiviae is placed as a sister taxon to all other myctophids and exhibits an unusual second copy of the tRNA-Met gene – a gene order rearrangement reminiscent of that found in the tribe Diaphini although our analyses show it to be independently derived. Most tribes are resolved in accordance with adult morphology although Gonichthyini is found within a subclade of the tribe Myctophini consisting of ctenoid scaled species. Mitogenomic sequence data from this study recognize 10 reciprocally monophyletic lineages within Myctophidae, with five of these clades delimited from additional rearranged gene orders or intergenic non-coding sequences.ConclusionsMitogenomic results from DNA sequences and unique gene orders corroborate morphology in phylogeny reconstruction and provide a likely scenario for the phylogenetic history of Myctophiformes. The extent of gene order rearrangements found within the mitochondrial genomes of myctophids is unique for phylogenetic purposes.