FIRST RECORD OF DENDROBAENA-ATTEMSI (MICHAELSEN) (OLIGOCHAETA, LUMBRICIDAE) IN SCANDINAVIA, WITH A CRITICAL-REVIEW OF ITS MORPHOLOGICAL VARIATION, TAXONOMIC RELATIONSHIPS AND GEOGRAPHICAL RANGE

Specimens of Dendrobaena attemsi (Michaelsen, 1902) are reported from a relict natural forest habitat in 'Nationalstadsparken', an urban nat ional park within the city of Stockholm, Sweden. They represent the no rthernmost record of the species and the first from Scandinavia. A mor phological comparison of the new material with conspecific samples fro m Italy and Turkey, and with literature data, shows that the typical t raits of the species (small body size, pigmentation pattern, long-stal ked spermathecae, hooked nephridial bladders, lack of hearts in xi) re main virtually invariant throughout its geographic range. A constancy is also observed in the regular nephropore alternation between setal l evels b and d as well as in several aspects of chaetotaxy, including t he relative size distribution of the clitellar genital setae b and the ir 'grooviness' (mean length of grooves/mean total setal length). Othe r features, e.g., the relative intersetal distances, the location and number of genital setae in the spermathecal and male areas, show intra specific variation. Based upon the apomorphic states of the nephridial features and the number of hearts, D. attemsi is tentatively regarded as an early branch of a clade comprising at least also the Balkan D. mahnerti, D. epirotica, D. pindonensis and D. rhodopensis. The superfi cially similar D. octaedra and D. decipiens do not belong to such a cl ade. Recent records of D. attemsi in natural habitats of the Czech Rep ublic and Germany suggest the possibility that, as is hypothesized for the western part of its range, also in Central Europe the species re- expanded northwards in postglacial times. Alternatively, the species w as introduced to Sweden by man, although a historical association with human settlements seems unlikely.