Genetic diversity and demographic instability in Riftia pachyptila tubeworms from eastern Pacific hydrothermal vents

<p>Abstract</p> <p>Background</p> <p>Deep-sea hydrothermal vent animals occupy patchy and ephemeral habitats supported by chemosynthetic primary production. Volcanic and tectonic activities controlling the turnover of these habitats contribute to demographic instability that erodes genetic variation within and among colonies of these animals. We examined DNA sequences from one mitochondrial and three nuclear gene loci to assess genetic diversity in the siboglinid tubeworm, <it>Riftia pachyptila</it>, a widely distributed constituent of vents along the East Pacific Rise and Galápagos Rift.</p> <p>Results</p> <p>Genetic differentiation (<it>F</it>_<it>ST</it>) among populations increased with geographical distances, as expected under a linear stepping-stone model of dispersal. Low levels of DNA sequence diversity occurred at all four loci, allowing us to exclude the hypothesis that an idiosyncratic selective sweep eliminated mitochondrial diversity alone. Total gene diversity declined with tectonic spreading rates. The southernmost populations, which are subjected to superfast spreading rates and high probabilities of extinction, are relatively homogenous genetically.</p> <p>Conclusions</p> <p>Compared to other vent species, DNA sequence diversity is extremely low in <it>R. pachyptila</it>. Though its dispersal abilities appear to be effective, the low diversity, particularly in southern hemisphere populations, is consistent with frequent local extinction and (re)colonization events.</p

Molecular characterization of Bathymodiolus mussels and gill symbionts associated with chemosynthetic habitats from the U.S. Atlantic margin.

Mussels of the genus Bathymodiolus are among the most widespread colonizers of hydrothermal vent and cold seep environments, sustained by endosymbiosis with chemosynthetic bacteria. Presumed species of Bathymodiolus are abundant at newly discovered cold seeps on the Mid-Atlantic continental slope, however morphological taxonomy is challenging, and their phylogenetic affinities remain unestablished. Here we used mitochondrial sequence to classify species found at three seep sites (Baltimore Canyon seep (BCS; ~400m); Norfolk Canyon seep (NCS; ~1520m); and Chincoteague Island seep (CTS; ~1000m)). Mitochondrial COI (N = 162) and ND4 (N = 39) data suggest that Bathymodiolus childressi predominates at these sites, although single B. mauritanicus and B. heckerae individuals were detected. As previous work had suggested that methanotrophic and thiotrophic interactions can both occur at a site, and within an individual mussel, we investigated the symbiont communities in gill tissues of a subset of mussels from BCS and NCS. We constructed metabarcode libraries with four different primer sets spanning the 16S gene. A methanotrophic phylotype dominated all gill microbial samples from BCS, but sulfur-oxidizing Campylobacterota were represented by a notable minority of sequences from NCS. The methanotroph phylotype shared a clade with globally distributed Bathymodiolus spp. symbionts from methane seeps and hydrothermal vents. Two distinct Campylobacterota phylotypes were prevalent in NCS samples, one of which shares a clade with Campylobacterota associated with B. childressi from the Gulf of Mexico and the other with Campylobacterota associated with other deep-sea fauna. Variation in chemosynthetic symbiont communities among sites and individuals has important ecological and geochemical implications and suggests shifting reliance on methanotrophy. Continued characterization of symbionts from cold seeps will provide a greater understanding of the ecology of these unique environments as well and their geochemical footprint in elemental cycling and energy flux

Sex‐specific markers undetected in green sunfish Lepomis cyanellus using restriction‐site associated DNA sequencing

We used restriction-site associated DNA sequencing for SNP discovery and genotyping of known-sex green sunfish Lepomis cyanellus DNA samples to search for sex-diagnostic single nucleotide polymorphisms (SNPs) and restriction-site associated sequences present in one sex and absent in the other. The bioinformatic analyses discovered candidate SNPs and sex-specific restriction-site associated sequences that fit patterns of male or female heterogametic sex determination systems. However, when primers were developed and tested, no candidates reliably identified phenotypic sex. The top performing SNP candidate (ZW_218) correlated with phenotypic sex 63.0% of the time and the presence-absence loci universally amplified in both sexes. We recommend further investigations that interrogate a larger fraction of the L. cyanellus genome. Additionally, studies on the effect of temperature and rearing density on sex determination, as well as breeding of sex-reversed individuals, could provide more insights into the sex determination system of L. cyanellus.12 month embargo; first published: 19 April 2022This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]