New species of Eurythenes from hadal depths of the Mariana Trench, Pacific Ocean (Crustacea: Amphipoda)

Abstract

Eurythenes S. I. Smith in Scudder, 1882 are one of the largest scavenging deep-sea amphipods (max. 154 mm) and are found in every ocean across an extensive bathymetric range from the shallow polar waters to hadal depths. Recent systematic studies of the genus have illuminated a cryptic species complex and highlighted the benefits of using a combination of morphological and molecular identification approaches. In this study, we present the ninth species, Eurythenes plasticus sp. nov., which was recovered using baited traps between the depths 6010 and 6949 m in the Mariana Trench (Northwest Pacific Ocean) in 2014. This new Eurythenes species was found to have distinct morphological characteristics and be a well-supported clade based on sequence variation at two mitochondrial regions (16S rDNA and COI). While this species is new to science and lives in the remote hadal zone, it is not exempt from the impacts of anthropogenic pollution. Indeed, one individual was found to have a microplastic fibre, 83.74% similar to polyethylene terephthalate (PET), in its hindgut. As this species has a bathymetric range spanning from abyssal to hadal depths in the Central Pacific Ocean basin, it offers further insights into the biogeography of Eurythenes.

Effect of microplastics in water and aquatic systems

“…The particle found was about 649.648 μm long and was 83.74% similar to PET, a common polymer used in bottles, food packaging, and textile fabrics was found in the guts of the species. The shrimp-like creature, about two inches long, was found 20,000 ft underwater in the Pacific Ocean (WESTON et al 2020 ) reveals that even creatures from undiscovered habitat are already polluted with plastics as they are feeding on MPs throughout their lifespan, which may have acute and permanent health consequences. Although the ecotoxicological effects of microplastic toxicity on deep-sea amphipods have yet to be studied, it is quite possible that the other undiscovered species living in the depths of pacific ocean are equally vulnerable to the ingestion of microplastic fibres (Peng et al 2020 ).…”

Eurythenes atacamensis sp. nov. (Crustacea: Amphipoda) exhibits ontogenetic vertical stratification across abyssal and hadal depths in the Atacama Trench, eastern South Pacific Ocean

“…nov. within Eurythenes was investigated with publicly available data in two datasets, namely, 16S and COI. The comparative sequences were selected to represent type material, highconfident identifications, or from defined undescribed lineages (Table 2; France and Kocher 1996;Escobar-Briones et al 2010;Havermans et al 2013;d'Udekem d'Acoz and Havermans 2015;Ritchie et al 2015;Havermans 2016;Narahara-Nakano et al 2018;Ritchie et al 2017;Horton et al 2020;Weston et al 2020a). The sequences associated with Eurythenes cf.…”

“…As with Eurythenes plasticus, individuals of E. atacamensis sp. nov. have been previously documented to ingest microplastics (Jamieson et al 2019;Weston et al 2020a). Eurythenes atacamensis sp.…”

“…Cryptic speciation with the gryllus-complex has since been confirmed by integrative taxonomic studies (Havermans et al 2013;Havermans 2016;Eustace et al 2016). Since 2015, Eurythenes has expanded from three to nine described species (d'Udekem d 'Acoz and Havermans 2015;Narahara-Nakano et al 2018;Weston et al 2020a). Furthermore, at least five distinct genetic lineages are awaiting formal description (France and Kocher 1996;Havermans et al 2013;Eustace et al 2016;Horton et al 2020) and more are likely to be discovered via expansion of sampling programs (Havermans 2016).…”

“…Smith in Scudder, 1882 are prevalent members of the deep ocean, benthopelagic community (Stoddart and Lowry 2004;Havermans 2016). This genus inhabits every ocean across an extensive bathymetric range-observed in polar waters (Ainley et al 1986;Bowman and Manning 1972), on the abyssal plains (Barnard 1961;Brandt et al 2012;Havermans 2016), and at hadal depths (Thurston et al 2002;Fujii et al 2013;Eustace et al 2016;Weston et al 2020aWeston et al , 2021. They have been the focus of ecological and physiological studies, including metabolism (Premke and Graeve 2009), feeding strategies (Hargrave 1985;Premke et al 2006;Blankenship and Levin 2007), population demographics (Ingram and Hessler 1987;Christiansen et al 1990;Thurston et al 2002;Blankenship et al 2006), and biomonitoring (Reid et al 2018).…”