Sequencing, Assembly, Expressed Sequence Tags and Microsatellite Loci for Three Freshwater Mussel Genomes: Alasmidonta heterodon, A. varicosa and Elliptio complanata

Unionids – freshwater mussels – constitute one of the most sensitive and rapidly declining faunal groups in the world.  They are imperiled mainly because they are filter feeders with a sedentary adult phase, making them uniquely susceptible to water pollution; further, many are late-maturing and all have a parasitic glochidial life stage which is parasitic upon particular species of fish, tying the status of the mussel to the demographic health of host population. Factors contributing to the decline of freshwater mussels include habitat degradation, urbanization, land use changes, dam construction, sedimentation, pollution, and ecological interactions with invasive fishes and mollusks. Little is known about their normal physiology and behavior of freshwater mussels, impeding conservation efforts. Knowledge of genes mediating adaptation and conferring resiliency in the face of ecological challenge is scant. Against this background, we have sequenced the whole genomes of dwarf wedgemussel (Alasmidonta heterodon), brook floater (Alasmidonta varicosa), and eastern elliptio (Elliptio complanata). We assembled contiguous sequences for each of the genomes using Newbler, the Roche 454 assembler program. We then identified expressed sequence tags (ESTs) and described microsatellite loci in each of the three genomes. A total of 818 open reading frames (ORFs) were identified for Alasmidonta heterodon, 1390 for Alasmidonta varicose and 1282 for Elliptio complanata. These data have been deposited at NCBI (http://www.ncbi.nlm.nih.gov/nuccore?term=Alismodanta%20varicosa). Identification of ESTs and microsatellite loci is ongoing, but will be completed well before the AFS meeting. The genomic information so gained should prove useful in advancing understanding adaptation in freshwater mussels and in study of population genetics and phylogeny.