Ecology and distribution of the Arctic Tadpole Shrimp Lepidurus arcticus (Branchiopoda, Notostraca) in the Fennoscandian Mountain Range and on the Svalbard Archipelago

Lepidurus arcticus is frequently found at sea level in the Svalbard archipelago, extending further south from 80°N into the tundra zone and at increasing altitudes in the Fennoscandian Mountain Range (Scandes) down to 59°N, spanning 2300 km. In this region, there are records of Lepidurus arcticus in at least 686 locations. In Svalbard, it is noted in 87 fishless ponds and two rivers with anadromous Arctic charr. In Bear Island, it inhabits 103 fishless ponds, eight lakes, and three rivers containing resident Arctic charr. In the Scandes, it is found in 483 locations, predominantly in deep, large lakes with fish. This demonstrates a greater adaptability to various habitats than other notostracan species. The species’ ability to withstand significant environmental changes since its emergence is attributed to its resilient eggs, which can endure both freezing and desiccation and remain viable for decades. Additionally, its reproductive flexibility, which creates egg banks of overlapping generations, helps buffer the population against environmental variability. While the embryonic phase may persist for decades in the Arctic, both the embryonic and postembryonic phases are typically completed within a year in the Scandes. Lepidurus arcticus can reproduce both sexually and asexually. Asexual reproduction enhances dispersal abilities, as single eggs or individuals can establish new populations. Predicted warming of freshwater habitats may significantly impact Lepidurus arcticus, as water temperature limits its distribution. With rising temperatures, L. arcticus will likely expand its range into the colder territories of Svalbard. In the Scandes, prolonged warmth could restrict its range, yet it may ascend in altitude in southern Scandes. In Svalbard, warmer water and prolonged open water seasons may boost production. This could make the lakes more similar to those in Bear Island, and thus, coexistence with fish could become more common. Therefore, baseline studies are needed for cold-adapted freshwater species such as Lepidurus arcticus.