Finds of Siboglinids (Annelida, Siboglinidae) in the Estuaries of the Largest Arctic Rivers Are Associated with Permafrost Gas Hydrates.

Gutless marine worms of the family Siboglinidae have been found in the estuaries of the largest Arctic rivers Yenisei, Lena, and Mackenzie. Siboglinid metabolism is provided by symbiotic chemoautotrophic bacteria. Strong salinity stratification is characteristic of the estuaries of the largest Arctic rivers and ensures a high salinity at depths of 25-36 m, where siboglinids were found. High methane concentrations, which are necessary for siboglinid metabolism, result from dissociation of permafrost gas hydrates under the influence of river runoff in the conditions of Arctic warming.

Distribution of Siboglinids (Annelida, Siboglinidae) in the Laptev Sea and Adjacent Areas of the Arctic Basin.

Biodiversity in the Laptev Sea was assessed for gutless marine worms of the family Siboglinidae (Annelida), whose metabolism is provided by symbiotic bacteria that oxidize hydrogen sulfide and methane. Seven siboglinid species were found within the geographical boundaries of the Laptev Sea, and another species was found in an adjacent sector of the Arctic Basin. The largest number of finds and the greatest biological diversity of siboglinids were observed in the eastern part of the Laptev Sea in a field of numerous methane flares. One find was made in the estuary area of the Lena River at a depth of 25 m. A possible association of siboglinids with methane seepage areas is discussed.

The Finding of Pogonophorans (Annelida, Siboglinidae) in the St. Anna Trough (Kara Sea) in an Area of Gas Hydrate Dissociation.

Representatives of pogonophorans (Annelida, Siboglinidae), whose vital activity is provided by symbiotic chemoautotrophic bacteria that oxidize methane and hydrogen sulfide, were found in the St. Anna Trough at depths of 539 and 437 m. The finding of pogonophorans suggests high concentrations of methane, which might result from dissociation of bottom gas hydrates under the influence of the influx of warm Atlantic water into the Kara Sea along the St. Anna Trough.

First Experience of Keeping Pogonophorans (Annelida: Siboglinidae) in Laboratory Conditions.

The article describes the parameters of maintaining the gutless symbiotrophic annelid Siboglinum fiordicum in laboratory conditions outside the marine environment for 64 days.

New Data on Distribution of Nereilinum murmanicum (Annelida, Siboglinidae) in the Barents Sea.

The article presents a report on the findings of representatives of frenulate pogonophorans Nereilinum murmanicum in the northern and central parts of the Barents Sea, which significantly expands the range of this species and provides guidance on its distribution in this basin. Here we present the coordinates of new finds with an indication of the depth. Find points were associated with data on known and potential hydrocarbon deposits.

The First Discovery of Pogonophora (Annelida, Siboglinidae) in the East Siberian Sea Coincides with the Areas of Methane Seeps.

Pogonophora or siboglinid tubeworms (Annelida, Siboglinidae) have been found in the East Siberian Sea for the first time. On the basis of the results of molecular phylogenetic analysis, the found specimens are presumably assigned to the genus Oligobrachia. The stations where the siboglinid tubeworms have been found are located in the area of methane seeps. This confirms the previously stated hypothesis about relationship of siboglinid tubeworm distribution with the areas of underwater methane seeps.

Obturacula of Vestimentifera (Annelida, Siboglinidae) Are Homological to the Dorsal Lips of the Polychaete of the Family Sabellidae.

We have conducted comparative analysis of the structure of the dorsal lips of the polychaete Eudistylia polymorpha from the family Sabellidae and the obturacula of Oasisia alvinae (Vestimentifera). It has been concluded that the obturacula of Vestimentifera are homologs of the dorsal lips of Polychaete from the family Sabellidae. It has been suggested that the head lobe of siboglinids of the subfamily Frenulata is homologous to the fused obturacula of Vestimentifera.

First Discovery of Pogonophora (Annelida, Siboglinidae) in the Kara Sea Coincide with the Area of High Methane Concentration.

Here we report the first finding of a frenulate pogonophoran (Annelida, Siboglinidae) in the southern part of the Kara Sea. This finding was made in the Yenisei Gulf in the region of the highest methane concentrations, resulting from the degradation of permafrost under the influence of river flow. It has been suggested that pogonophorans are indicators of hydrocarbon manifestations of various genesis.

Siboglinids (Annelida, Siboglinidae) as Possible Hydrocarbon Indicators as Exemplified by the Sea of Okhotsk.

The geographic and bathymetric distribution of siboglinids in the Sea of Okhotsk was studied. At least 75% of all siboglinid findings were at a depth up to 400 m. Most of them were concentrated in the northwestern part of the shelf. Comparison of the data on siboglinid distribution in the Sea of Okhotsk and the aggregate geological data on hydrocarbon distribution showed that, in the Sea of Okhotsk, siboglinids were mostly in the regions of hydrocarbon manifestations, but they were absent in the central areas with the minimum methane and hydrocarbon concentrations in both benthic sediments and the uppermost water layers.

Changes in Body Proportions during Growth of the Hydrothermal Vestimentiferan Oasisia alvinae Jones 1985 (Annelida, Siboglinidae).

During the growth of hydrothermal vestimentiferan Oasisia alvinae the trunk part of body was found to be elongated (from 51 to 83.4% of the overall body length), while the relative dimensions of all other body regions decreased. This was related to the enhanced trophosome and gonad development in the trunk part. We suppose that predominant trunk growth is a common feature of all vestimentiferans.

Protonephridial Excretory System in Vestimentifera (Siboglinidae, Annelida).

Ultrastructural study of the excretory tree of vestimentifera Ridgeia piscesae has shown that it consists of tubules that are blind at their distal ends. The tubules are lined with ciliated cells and have one or two multiciliated terminal cell(s) at the distal ends. In the tubule walls, there are putative ultrafiltration sites. The excretory tree tubules are interpreted as the secondary protonephridia.