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Jawless Fishes of the World (Vol. 1)
Abstract
Hagfishes and lampreys, both examples of jawless fishes, are elongated, eel-like animals lacking paired fins, and are the only living representatives of ancient creatures that gave rise to current species of fish and, eventually, humans.
This volume provides an overview of the current status of knowledge on a variety of topics related to jawless fishes, including their taxonomy, zoogeography, phylogeny, molecular biology, evolution, life history, role in the ecosystem, and fisheries and management of hagfishes and lampreys worldwide. This is the first book dealing exclusively with the various aspects of jawless fish species throughout the world.
It brings together a number of papers providing new data on jawless fishes. It offers readers a range of useful information within a single reference, and reflects the growing appreciation for hagfishes and lampreys worldwide.
... More recently, PGR was also discovered and characterized in the sea lamprey (Petromyzon marinus) ( Smith et al., 2009Smith et al., , 2012Timoshevskiy et al., 2016;Bryant et al., 2016). The lineage leading to P. marinus diverged from the ancestral lineage of all other extant (jawed) vertebrates and the lineage leading to hagfish approximately 500 million years ago (MYA) ( Orlov and Beamish, 2016), raising questions as to the ancestry and evolutionary significance of PGR in P. marinus, ancestral gnathostome lineages and the ancestral vertebrate lineage. Recent efforts have made progress in identifying the gene targets and cellular mechanisms of PGR in P. marinus ( Smith et al., 2012;Timoshevskiy et al., 2016;Bryant et al., 2016). ...
In most multicellular organisms, the structure and content of the genome is rigorously maintained over the course of development. However some species have evolved genome biologies that permit, or require, developmentally regulated changes in the physical structure and content of the genome (programmed genome rearrangement: PGR). Relatively few vertebrates are known to undergo PGR, although all agnathans surveyed to date (several hagfish and one lamprey: Petromyzon marinus) show evidence of large scale PGR. To further resolve the ancestry of PGR within vertebrates, we developed probes that allow simultaneous tracking of nearly all sequences eliminated by PGR in P. marinus and a second lamprey species (Entosphenus tridentatus). These comparative analyses reveal conserved subcellular structures (lagging chromatin and micronuclei) associated with PGR and provide the first comparative embryological evidence in support of the idea that PGR represents an ancient and evolutionarily stable strategy for regulating inherent developmental/genetic conflicts between germline and soma.
... More recently, PGR was also discovered and characterized in the sea lamprey (Petromyzon marinus) (Smith et al., 2009(Smith et al., , 2012Timoshevskiy et al., 2016;Bryant et al., 2016). The lineage leading to P. marinus diverged from the ancestral lineage of all other extant (jawed) vertebrates and the lineage leading to hagfish approximately 500 million years ago (MYA) (Orlov and Beamish, 2016), raising questions as to the ancestry and evolutionary significance of PGR in P. marinus, ancestral gnathostome lineages and the ancestral vertebrate lineage. ...
Next generation sequencing data can be mined for highly informative single nucleotide polymorphisms (SNPs) to develop high-throughput genomic assays for non-model organisms. However, choosing a set of SNPs to address a variety of objectives can be difficult because SNPs are often not equally informative. We developed an optimal combination of 96 high-throughput SNP assays from a total of 4,439 SNPs identified in a previous study of Pacific lamprey (Entosphenus tridentatus), and used them to address four disparate objectives: parentage analysis, species identification, and characterization of neutral and adaptive variation. Nine of these SNPs are FST outliers, and five of these outliers are localized within genes and significantly associated with geography, run-timing, and dwarf life history. Two of the 96 SNPs were diagnostic for two other lamprey species which are morphologically indistinguishable at early larval stages and are sympatric in the Pacific Northwest. The majority (85) of SNPs in the panel were highly informative for parentage analysis- i.e. putatively neutral with high minor allele frequency across the species' range. Results from three case studies are presented to demonstrate the broad utility of this panel of SNP markers in this species. As Pacific lamprey populations are undergoing rapid decline, these SNPs provide an important resource to address critical uncertainties associated with the conservation and recovery of this imperiled species.
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