Complete mitochondrial genomes of the anadromous and resident forms of the lamprey Lethenteron camtschaticum

Investigating Diadromy in Fishes and Its Loss in an -Omics Era

Diadromy, the predictable movements of individuals between marine and freshwater environments, is biogeographically and phylogenetically widespread across fishes. Thus, despite the high energetic and potential fitness costs involved in moving between distinct environments, diadromy appears to be an effective life history strategy. Yet, the origin and molecular mechanisms that underpin this migratory behavior are not fully understood. In this review, we aim first to summarize what is known about diadromy in fishes; this includes the phylogenetic relationship among diadromous species, a description of the main hypotheses regarding its origin, and a discussion of the presence of non-migratory populations within diadromous species. Second, we discuss how recent research based on -omics approaches (chiefly genomics, transcriptomics, and epigenomics) is beginning to provide answers to questions on the genetic bases and origin(s) of diadromy. Finally, we suggest future directions for -omics research that can help tackle questions on the evolution of diadromy.

The mitogenomes of the pouched lamprey (Geotria australis) and least brook lamprey (Lampetra aepyptera) with phylogenetic considerations

We report the mitogenomes of the pouched lamprey (Geotria australis) and least brook lamprey (Lampetra aepyptera) in the families Geotriidae and Petromyzontidae, respectively. Both of the mitogenomes contain the 37 typical vertebrate genes. Their gene order and contents are identical to those of previously described lamprey mitogenomes. The mitogenome of G. australis (17 080 bp) is the largest among the 10 reported lamprey mitogenomes, owed to two long noncoding regions. The mitogenome of L. aepyptera is 77 bp longer (16 236 bp) than that of the congeneric European river lamprey L. fluviatilis, a size difference mostly due to different copy numbers of tandem repeats in the noncoding regions. The phylogenetic analysis supports that the pouched lamprey (Geotriidae) diverged earlier from the common ancestor of lampreys than the Petromyzonids, and the placement of the least brook lamprey in the genus Lampetra.