Polymetallic nodule mining is a growing commercial interest over the past three decades. It is critical to accurately estimate biodiversity before any minerals are exploited in the Clarion-Clipperton Zone (CCZ) in the Northeast Pacific Ocean. Scavenging amphipods are a large group in the abyssal biota and play an important role in the nutrient cycling system. This study uses both mitochondrial (COI) and nuclear (28S rRNA) DNA markers to investigate genetic diversity and connectivity in Abyssorchomene distinctus (Lysianassoidea – Uristidae) (Birstein & Vinogradov, 1960). The genetic sequences of 113 sampled individuals of Abyssorchomene distinctus, which originated from the CCZ, the Discol Experimental Area (DEA), the Atacama Trench and the Southeast Indian Ridge, revealed the absence of cryptic diversity for A. distinctus on a global scale. The findings contrasted with those for other closely related scavenging amphipods, which revealed the presence of cryptic species. Population genetics analyses calculated a low haplotype diversity (Hd) within the A. distinctus population across the Pacific Ocean, while a high Hd was found in the Indian Ocean populations. This is the first study to date providing preliminary indications of a possible genetic connectivity of the scavenging amphipod species Abyssorchomene distinctus between the CCZ and DEA, being geographically separated by a vast distance of 5,000 km. Shared haplotypes were also found between the CCZ, DEA, Atacama Trench and the Southeast Indian Ridge in the COI mitochondrial DNA dataset , which was congruent with results from previous studies on other scavenging amphipods.
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Polar ecosystems feature among the last pristine areas of planet Earth, but also among the fastest changing due to global change. The long isolation history of the Southern Ocean has led to high levels of endemism, resulting in a hotspot of biodiversity for many taxa, including crustaceans (Malacostraca). Genomes represent the blueprint of this long evolution. Geographic isolation in combination with harsh and challenging sampling conditions, has left considerable biological knowledge gaps in the Southern Ocean. Closing these knowledge gaps is challenging for Antarctic amphipods because their genome sizes are highly variable and they are hard to sample. Genome size of amphipods are widely varying, ranging from 0.68 to 64.62 pg with an average of 12.85 pg (± 4.46 pg). Unfortunately, information on the genome size of amphipods remains limited, especially from polar regions. Just 65 records of amphipod genome sizes are listed in the Animal Genome Size Database, of which 17 marine species. To close the knowledge gap, I used flow cytometry to estimate the genome size of 32 Antarctic amphipod species. I successfully estimated genome sizes for 20 species, ranging from 0.45 pg to 57.28 pg (> 120-fold difference). Preliminary analyses do not show any significant correlation between depth and genome size or body size and genome size. The results provide a valuable addition to the inventory of the genome size of amphipods, especially from extreme environments.
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