716 BIOLOGY OF THE SEAS OF THE U.S.S.R. 



new expedition, and there is little doubt that soon this group will comprise 

 some hundreds of species. 



Judging by the intensive researches of the Vityaz, it is possible so far to assume 

 to some extent that the main abundance of Pogonophorae species is concen- 

 trated in the Far Eastern seas and the northwestern part of the Pacific Ocean 

 (Fig. 337), as well as in the northern hemisphere. Only forms of the genus 

 Siboglinum, Oligobrachia and Polybrachia the richest in species, have so far 

 been found in the Atlantic Ocean. Only one species of this genus has been 

 recorded in Antarctic waters. Diplobranchia belajevi is the only species of 

 this group so far reported from the Indian Ocean. Soviet expeditions have 

 discovered in the Arctic basin Polybranchia gorbunovi in its eastern sector and 

 Siboglinum hyperboreum off the eastern coast of Greenland ; these have been 

 found also in the Bering Sea. The Pacific Ocean is generally much richer in 

 Pogonophorae, although they are unevenly distributed there. Only two 

 species, Krampolinum galatheae and Lamellisabella zachsi are known from the 

 eastern part of the Pacific, the Gulf of Panama. Galathea and Vityaz trawl- 

 ing in the Philippines and in the Mariana, Tonga and Kermadec trenches have 

 not produced any Pogonophorae. The seas of the Malayan Archipelago have a 

 more abundant Pogonophora fauna. However, so far only Siboglinum weberi, 

 S. pinnulatum, S. taeniaphorum and Galathealinum brunni are known there — 

 only four species of two genera. Four species of Siboglinum were found in the 

 northern part of the Coral Sea {S. microcephalum, S. buccelliferum, S. robus- 

 tum and S. frenigerum). The Vityaz found four species of Siboglinum (S. 

 vinculatum, S. variabilis, S. bogorovi and S. tenuis) in the waters of the 

 northern island of New Zealand. 



Thus 20 species of Pogonophorae belonging to six genera are known out- 

 side the northwestern part of the Pacific, while in the latter 22 species belong- 

 ing to nine genera have been found. Twenty-five new species of Pogonophora 

 have been found in the Indian Ocean {Vityaz, 1959-60). 



The Pogonophorae are typical deep-water organisms ; in three areas, how- 

 ever, they rise to depths which are unusual for them : in the Sea of Okhotsk, 

 {Siboglinum caulleryi to 22 m, S. plumosum to 119 m and Oligobrachia dogieli 

 to 142 m) ; in the seas of the Malayan Archipelago {Siboglinum pinnulatum and 

 S. taeniaphorum to 260 m) ; and in the Atlantic Ocean {Siboglinum ermani, 

 S. atlanticum, S. inermis Oligobrachia ivanovi, and Polybrachia capillaris to 

 300 to 340 m; and in the Barents Sea (Nereilinum, to 170 m) ). Many of 

 these species descend to great depths, some even to the ultra-abyssal (for 

 instance, Siboglinum caulleryi from 22 m to 8,164 m). As to their ascent to the 

 upper layers in the Sea of Okhotsk, we are dealing, apparently, with a case 

 similar to the rising of deep-water forms to the surface waters in the Arctic, 

 a phenomenon well known for the Atlantic sector of the Arctic basin, 

 the Sea of Okhotsk and the Antarctic. The ascent of deep-water forms 

 to shallow depths has neither been investigated in detail nor sufficiently 

 explained. 



E. Vinogradova has recently studied this problem (1955). She points out 

 that the ascent of the deep-water fauna to shallow depths unusual for them 

 has been observed also in tropical latitudes. 'This kind of ascent is very 



