The LTR retrotransposon is a selfish endogenous element in the soft-shell clam genome that was first detected because of its dramatic amplification in bivalve transmissible neoplasia afflicting the species. We amplified and sequenced related retrotransposons from the genomic DNA of many other bivalve species, finding evidence of horizontal transfer of retrotransposons from the genome of one species to another. First, the phylogenetic tree of the-like elements from 19 bivalve species is markedly discordant with host phylogeny, suggesting frequent cross-species transfer throughout bivalve evolution. Second, sequences nearly identical to were identified in the genomes of Atlantic razor clams and Baltic clams, indicating recent transfer. Finally, a search of the National Center for Biotechnology Information sequence database revealed that-like elements are present in the genomes of completely unrelated organisms, including zebrafish, sea urchin, acorn worms, and coral. Phylogenetic incongruity, a patchy distribution, and a higher similarity than would be expected by vertical inheritance all provide evidence for multiple long-distance cross-phyla horizontal transfer events. These data suggest that over both short- and long-term evolutionary timescales, -like retrotransposons, much like retroviruses, can move between organisms and integrate new copies into new host genomes.

Dogs provide an ideal model for study as they have the most phenotypic diversity and known naturally occurring diseases of all non-human land mammals. Thus, data related to dog health present many opportunities to discover insights into health and disease outcomes. Here, we describe several sources of veterinary medical big data that can be used in research. These sources include medical records from primary medical care centers or referral hospitals, medical claims data from animal insurance companies, and datasets constructed specifically for research purposes. No data source provides information that is without limitations, but large-scale, prospective, longitudinally collected data from dog populations are ideal for further research as they offer many advantages over other data sources.

Bivalve specimens from legacy frozen tissue collections, and others freshly obtained, were surveyed for the presence of the Steamer long terminal repeat (LTR)-retrotransposon associated with disseminated hemic neoplasia of the soft-shelled clam Mya areneria. Of 22 species investigated using primers for the pol region, only Atlantic M. arenaria, Atlantic and North Sea razor clams Ensis directus, and Baltic clams Macoma balthica from the North Sea were found to possess copies of Steamer in their genomes. Notably, close relatives like Mya truncata and Siliqua patula did not exhibit evidence of Steamer. Amplified Steamer sequences were uniformly identical in all M. areneria specimens, and were highly variable across specimens of E. directus. Variation in the latter included nucleotide polymorphisms among and within individuals as well as length variation in 2 specimens corresponding to the deletion of a predicted stable hairpin structure. Results implicate Atlantic razor clams as the proximal source for horizontal transmission of Steamer among ecologically similar yet markedly distantly related bivalves. The consequences of cross-species transmission of the Steamer retrotransposon are unknown, and the finding of Steamer in 3 bivalve species suggests that further spread is possible. KEY WORDS: Disseminated neoplasia · Hemic neoplasia · Retrotransposon · Steamer · Bivalvia · CancerResale or republication not permitted without written consent of the publisher Dis Aquat Org 124: [165][166][167][168] 2017 pression of the Steamer retrotransposon. Steamer is a long terminal repeat (LTR)-retrotrans poson in the Mag family of Ty3/Gypsy elements, complete with a single open reading frame encoding gag and pol genes. Retrotransposons are present in genomic DNA and replicate through reverse transcription of an mRNA transcript into DNA, followed by integration into a new location within the genomic DNA of a cell. As they are notably lacking a retroviral env gene, they are not expected to be able to transfer from cell to cell, as retroviruses do. Similar retrotransposons have been identified in the genomes of 3 other bivalve species known to have transmissible neoplasias, one of which seems to cross the species boundary (Metzger et al. 2016).To date, the Steamer retrotransposon itself is un ique to M. arenaria. Here we examined legacy bio diversity collections and freshly acquired bivalve tissues for the presence of a Steamer signature in their genomes in a manner that might (1) better elucidate whether disseminated neoplasias are ecologically or phylogenetically determined and (2) shed light on the potential for horizontal spread and genomic modification by Steamerlike retrotransposons in the marine environment. MATERIALS AND METHODSBivalve tissue samples were obtained from the American Museum of Natural History's Ambrose Monell Cryo Collection (AMCC), and included 22 species from the North Atlantic (see Table S1 in the Supplement at www. int-res. com/ articles/ suppl/ d124 p165 _ supp. pdf). Fresh specimens of steam...