Range extensions of Pacific bone-eating worms (Annelida, Siboglinidae, Osedax).

First described in 2004 off California, worms are now known from many of the world's oceans, ranging from 10 to over 4000 m in depth. Currently, little is known about species ranges, since most descriptions are from single localities. In this study, we used new sampling in the north-eastern Pacific and available GenBank data from off Japan and Brazil to report expanded ranges for five species: , , , and .

Allopatric and Sympatric Drivers of Speciation in Alviniconcha Hydrothermal Vent Snails.

Despite significant advances in our understanding of speciation in the marine environment, the mechanisms underlying evolutionary diversification in deep-sea habitats remain poorly investigated. Here, we used multigene molecular clocks and population genetic inferences to examine processes that led to the emergence of the six extant lineages of Alviniconcha snails, a key taxon inhabiting deep-sea hydrothermal vents in the Indo-Pacific Ocean. We show that both allopatric divergence through historical vicariance and ecological isolation due to niche segregation contributed to speciation in this genus.

Zooplankton biogeographic boundaries in the California Current System as determined from metabarcoding.

Within the southern California Current ecosystem there are two well-documented breaks in marine community structure at Point Conception and Punta Eugenia. We explored the presence of similar breaks in a diverse zooplankton community through metabarcoding of mixed net tow tissue samples collected during an expedition from Monterey to Baja California in February of 2012. We recovered a high diversity of species as well as patterns of species presence that align with their previously documented ranges in this region.

A new species of the live-bearing fish genus from northern Mexico (Cyprinodontiformes, Poeciliidae).

, is described based on seven specimens (17.9-26.7 mm SL) from the Río Concepción (also known as Río Magdalena), Sonora, Mexico.

Host hybridization as a potential mechanism of lateral symbiont transfer in deep-sea vesicomyid clams.

Deep-sea vesicomyid clams live in mutualistic symbiosis with chemosynthetic bacteria that are inherited through the maternal germ line. On evolutionary timescales, strictly vertical transmission should lead to cospeciation of host mitochondrial and symbiont lineages; nonetheless, examples of incongruent phylogenies have been reported, suggesting that symbionts are occasionally horizontally transmitted between host species. The current paradigm for vesicomyid clams holds that direct transfers cause host shifts or mixtures of symbionts.

An inordinate fondness for Osedax (Siboglinidae: Annelida): Fourteen new species of bone worms from California.

We incorporate DNA sequences from a comprehensive sampling of taxa to provide an updated phylogeny of Osedax and discuss the remarkable diversity of this clade of siboglinids. We formally describe 14 new species of Osedax from Monterey Bay, California, USA, raising the total number of properly named Osedax species to 25. These new species had formerly been recognized by informal names in various publications, and on GenBank.

Hydrothermal vent fields discovered in the southern Gulf of California clarify role of habitat in augmenting regional diversity.

Hydrothermal vent communities are distributed along mid-ocean spreading ridges as isolated patches. While distance is a key factor influencing connectivity among sites, habitat characteristics are also critical. The Pescadero Basin (PB) and Alarcón Rise (AR) vent fields, recently discovered in the southern Gulf of California, are bounded by previously known vent localities (e.

Geographical structure of endosymbiotic bacteria hosted by Bathymodiolus mussels at eastern Pacific hydrothermal vents.

Background: Chemolithoautotrophic primary production sustains dense invertebrate communities at deep-sea hydrothermal vents and hydrocarbon seeps. Symbiotic bacteria that oxidize dissolved sulfur, methane, and hydrogen gases nourish bathymodiolin mussels that thrive in these environments worldwide. The mussel symbionts are newly acquired in each generation via infection by free-living forms.

Widespread introgression in deep-sea hydrothermal vent mussels.

Background: The analysis of hybrid zones is crucial for gaining a mechanistic understanding of the process of speciation and the maintenance of species boundaries. Hybrid zones have been studied intensively in terrestrial and shallow-water ecosystems, but very little is known about their occurrence in deep-sea environments. Here we used diagnostic, single nucleotide polymorphisms in combination with one mitochondrial gene to re-examine prior hypotheses about a contact zone involving deep-sea hydrothermal vent mussels, Bathymodiolus azoricus and B.

Population subdivision of hydrothermal vent polychaete Alvinella pompejana across equatorial and Easter Microplate boundaries.

Background: The Equator and Easter Microplate regions of the eastern Pacific Ocean exhibit geomorphological and hydrological features that create barriers to dispersal for a number of animals associated with deep-sea hydrothermal vent habitats. This study examined effects of these boundaries on geographical subdivision of the vent polychaete Alvinella pompejana. DNA sequences from one mitochondrial and eleven nuclear genes were examined in samples collected from ten vent localities that comprise the species' known range from 23°N latitude on the East Pacific Rise to 38°S latitude on the Pacific Antarctic Ridge.

Complete mitochondrial genome of the headwater livebearer, : the mother of clones.

The sexually reproducing fish, (Actinopterygii, Cyprinodontiformes, Poeciliidae), is the maternal ancestor of six hybrid biotypes that reproduce clonally. The gene content and order of its 16,818 bp mitochondrial genome is virtually identical with that of other sexually reproducing poeciliid fishes, providing no evidence for a mitochondrial involvement in the origins of all-female reproduction.

Biophysical and Population Genetic Models Predict the Presence of "Phantom" Stepping Stones Connecting Mid-Atlantic Ridge Vent Ecosystems.

Deep-sea hydrothermal vents are patchily distributed ecosystems inhabited by specialized animal populations that are textbook meta-populations. Many vent-associated species have free-swimming, dispersive larvae that can establish connections between remote populations. However, connectivity patterns among hydrothermal vents are still poorly understood because the deep sea is undersampled, the molecular tools used to date are of limited resolution, and larval dispersal is difficult to measure directly.

New deep-sea species of Xenoturbella and the position of Xenacoelomorpha.

The discovery of four new Xenoturbella species from deep waters of the eastern Pacific Ocean is reported here. The genus and two nominal species were described from the west coast of Sweden, but their taxonomic placement remains unstable. Limited evidence placed Xenoturbella with molluscs, but the tissues can be contaminated with prey.

Complete mitochondrial genome of hydrothermal vent clam Calyptogena magnifica.

The mitochondrial genome of the hydrothermal vent clam Calyptogena magnifica (Bivalvia, Veneroida, Vesicomyidae) is reported for the first time in this study. The total length of its mitochondrial genome is 19 738 bp with overall GC content of 31.6%.

A dwarf male reversal in bone-eating worms.

Darwin hypothesized that sexes in a species should be similar unless sexual selection, fecundity selection, or resource partitioning has driven them apart. Male dwarfism has evolved multiple times in a range of animals, raising questions about factors that drive such extreme size dimorphism. Ghiselin noted that dwarf males are more common among smaller marine animals, and especially among sedentary and sessile species living at low densities, where mates are difficult to find, or in deep-sea environments with limited energy sources.

Complete mitochondrial genome of the hydrothermal vent tubeworm, Ridgeia piscesae (Polychaeta, Siboglinidae).

The complete mitochondrial genome of Ridgeia piscesae (Polychaeta, Siboglinidae), one of the dominant taxa in deep-sea hydrothermal vents, is reported here for the first time. The R. piscesae mitogenome is 15,002 bp in total length and includes 13 protein-coding gene sequences, small and large rRNA sequences and 22 tRNA sequences.

Larvae from deep-sea methane seeps disperse in surface waters.

Many species endemic to deep-sea methane seeps have broad geographical distributions, suggesting that they produce larvae with at least episodic long-distance dispersal. Cold-seep communities on both sides of the Atlantic share species or species complexes, yet larval dispersal across the Atlantic is expected to take prohibitively long at adult depths. Here, we provide direct evidence that the long-lived larvae of two cold-seep molluscs migrate hundreds of metres above the ocean floor, allowing them to take advantage of faster surface currents that may facilitate long-distance dispersal.

Genomic versatility and functional variation between two dominant heterotrophic symbionts of deep-sea Osedax worms.

An unusual symbiosis, first observed at ~3000 m depth in the Monterey Submarine Canyon, involves gutless marine polychaetes of the genus Osedax and intracellular endosymbionts belonging to the order Oceanospirillales. Ecologically, these worms and their microbial symbionts have a substantial role in the cycling of carbon from deep-sea whale fall carcasses. Microheterogeneity exists among the Osedax symbionts examined so far, and in the present study the genomes of the two dominant symbionts, Rs1 and Rs2, were sequenced.

A hybrid zone between Bathymodiolus mussel lineages from eastern Pacific hydrothermal vents.

Background: The inhabitants of deep-sea hydrothermal vents occupy ephemeral island-like habitats distributed sporadically along tectonic spreading-centers, back-arc basins, and volcanically active seamounts. The majority of vent taxa undergo a pelagic larval phase, and thus varying degrees of geographical subdivision, ranging from no impedance of dispersal to complete isolation, often exist among taxa that span common geomorphological boundaries. Two lineages of Bathymodiolus mussels segregate on either side of the Easter Microplate, a boundary that separates the East Pacific Rise from spreading centers connected to the Pacific-Antarctic Ridge.

The spatial scale of genetic subdivision in populations of Ifremeria nautilei, a hydrothermal-vent gastropod from the southwest Pacific.

Background: Deep-sea hydrothermal vents provide patchy, ephemeral habitats for specialized communities of animals that depend on chemoautotrophic primary production. Unlike eastern Pacific hydrothermal vents, where population structure has been studied at large (thousands of kilometres) and small (hundreds of meters) spatial scales, population structure of western Pacific vents has received limited attention. This study addresses the scale at which genetic differentiation occurs among populations of a western Pacific vent-restricted gastropod, Ifremeria nautilei.

Not whale-fall specialists, Osedax worms also consume fishbones.

Marine annelid worms of the genus Osedax exploit sunken vertebrate bones for food. To date, the named species occur on whale or other mammalian bones, and it is argued that Osedax is a whale-fall specialist. To assess whether extant Osedax species could obtain nutrition from non-mammalian resources, we deployed teleost bones and calcified shark cartilage at approximately 1000 m depth for five months.

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

Background: 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, Riftia pachyptila, a widely distributed constituent of vents along the East Pacific Rise and Galápagos Rift.

Genetic diversity and connectivity of deep-sea hydrothermal vent metapopulations.

Deep-sea hydrothermal vents provide ephemeral habitats for animal communities that depend on chemosynthetic primary production. Sporadic volcanic and tectonic events destroy local vent fields and create new ones. Ongoing dispersal and cycles of extirpation and colonization affect the levels and distribution of genetic diversity in vent metapopulations.