2023

Qvenild, Tore; Arnekleiv, Jo Vegar; Lakka, Hanna-Kaisa

Acanthobdellida, a group of annelid worms, comprise two known species, one of which, Acanthobdella peledina, is the only recorded in Fennoscandia. The great scientific interest in the Acanthobdellida is due to its special combination of oligochaetous and hirudinean characters (leeches with setae), suggesting their intermediate role between Oligochaeta and Euhirudinea (true leeches). The early morphological studies by Livanow (1906) characterising the species as a “missing link” has now been confirmed with modern phylogenetic methods which stated Acanthobdellida as sister group to Euhirudinea. Acanthobdella peledina is a cold water adapted species, confined to the northern parts of the northern hemisphere. In total 83 % of the 119 known locations worldwide are situated in Fennoscandia, most of them in the upper part of the river systems in Northern Sweden and Northern Finland which drain to the Bothnian Sea. Some of the southern localities are in the upper parts of the river systems Östre Dalälven River, Trysilelva River and Glomma River. From the Glomma River they have spread to the western running watercourses of the Gaula River and the Nidelva River. In Troms they are known from four watercourses. In the regulated rivers, the Nidelva River and the Barduelva River, they are common all the way down to the coastal parts. From the Russian part of Fennoscandia there are known six localities. In addition, 16 localities are known from Siberia and 4 from Alaska. There are indications of climate driven range retractions of this cold adapted species. Alpine and Arctic ecosystems are very vulnerable to climate change which may pose a serious threat to this “living fossil”.