A first look at xenophyophores (Rhizaria, Foraminifera) in the lower bathyal Bering Sea and abyssal areas adjacent to the Aleutian Trench

Abstract

Xenophyophores are an abundant component of the megafauna in parts of the equatorial and temperate North Pacific, but few records exist of these giant agglutinated foraminifera in northern North Pacific and adjacent waters. Here, we present a preliminary survey of xenophyophores from the bathyal Bering Sea (∼3500 m depth) and at abyssal depths (4294–6555 m) adjacent to the Aleutian Trench, based on collected material, mainly fragments, and seafloor images. The dominant xenophyophore in the Bering Sea is a reticulated form that yielded DNA sequences identical to those obtained from Syringammina limosa, a species described from > 2700 km to the west in the Sea of Okhotsk. Also visible in seafloor photographs were various plate-like forms, often with upturned, undulating rims, but also branching plates and other more complicated morphotypes that probably represent distinct species. At stations close to the Aleutian Trench, core and epibenthic sledge samples yielded xenophyophores at seven of the 16 sampling sites. At least eleven morphospecies were recognised among those collected, none of which resembled S. limosa or the plate-like Bering Sea forms. Seafloor images revealed 16 fairly distinct domed or plate-like morphotypes three of these are possibly represented among the collected specimens, making a total of around 24 morphotypes or morphospecies. A few images show morphotypes similar to those seen in the Bering Sea. Our results suggests that xenophyophores are as diverse in the northern North Pacific as they are elsewhere in the Pacific Ocean.