Kinorhyncha community in the Aleutian Trench (North Pacific Ocean) with the description of a new Cristaphyes species (Allomalorhagida, Pycnophyidae)

• Kinorhyncha community of the Aleutian Trench consist of 10 species. • A new Kinorhyncha species, Cristaphyes unangax sp. nov., is described. • The axis has high abundance may be due to organic matter accumulation. • The high abundance at a slope site (abyssal), may result from upwelling or terraces. • Meiofauna can disperse across the Aleutian and Kuril-Kamchatka trenches. Several species of trench-dwelling meiofaunal animals, including Kinorhyncha, have been described in recent years; however, our knowledge on kinorhynchs inhabiting abyssal and even hadal depths is still extremely scarce. In the present study, we explore the Kinorhyncha community of the Aleutian Trench, North Pacific Ocean, an under-sampled region in terms of meiofauna. As a result, a new species of Cristaphyes inhabiting abyssal and hadal depths of the trench is described. Cristaphyes unangax sp. nov. is characterized by the presence of middorsal processes on segments 1 – 10, with the last one extending well-beyond the posterior margin of the trunk. Cristaphyes unangax sp. nov. thus becomes the fourth hadal species described within the phylum Kinorhyncha. In terms of biodiversity, abundance of adult kinorhynchs remains relatively low along the trench’s depth gradient (c.a. 3.500 – 7.200 m), except at two sites: one at the axis and another at the slope. The higher abundance at the axis aligns with patterns in other trenches, where organic matter accumulation enhances microbial activity, supporting meiofaunal communities. The elevated specimens at the slope station, located at abyssal depth, may result from Aleutian upwelling currents or trench terraces that facilitate food deposition. The Kinorhyncha community in the Aleutian Trench is dominated by Echinoderes ultraabyssalis and includes another nine species, many shared with the North Pacific and Arctic. These findings suggest that meiofauna in the North Pacific can disperse across bathymetric barriers, potentially linking the Aleutian and Kuril-Kamchatka trenches. Additionally, the Aleutian Trench may serve as a migration corridor for meiofauna between the North Pacific and Arctic, aided by strong bottom currents. Zoobank : urn:lsid:zoobank.org:pub:56D1BA0B-3D9F-4547-84BC-C9BAFCA1D220