A taxonomic study of some Swedish Enchytraeidae (Oligochaeta), with descriptions of four new species and notes on the genus Fridericia

A taxonomic account of twenty-nine of the enchytraeid species occurring in Nationalstadsparken, an urban national park in Stockholm, Sweden, is given. Four species are new to science: Cernosvitoviella microtheca sp. n. is cha racterized by large, coarsely granular coelomocytes, small spermathecae con fined to V, sperm funnels funnel-shaped and sperm ducts ectally swollen and stiffened. Fridericia christeri sp. n. is distinguished by its constant la ck of spermathecae (confirmed by observations in laboratory cultures), a bi setose condition of all its postclitellar lateral bundles, and the regular arrangement of its clitellar cells; this species also lives in the island o f Gland in the Baltic sea. Fridericia ulrikae sp. n. has thin-walled, cylin drical spermathecal ampullae with stalked, sharply bent diverticula, and la rge penial bulbs, with 'redundant' glandular tissue flanking the basic cush ion. Fridericia waldenstroemi sp. n. is characterized by its peripherally g ranular coelomocytes, the preclitellar location of its chylus cells, and th e two-tone glandular cover of its sperm funnels. Another twelve species (Ce rnosvitoviella minor, Enchytraeus bulbosus, E. lacteus, Fridericia callosa, F. gracilis,,E isseli, F. leydigi, F. paranemoralis, F. singula, Hemifride ricia parva, Lumbricillus arenarius, Stercutus niveus) are new records for Sweden. Descriptions of the taxa in vivo are supplemented with observations on whole-mounted specimens, with a view to improving the standard of speci es diagnoses and helping identification of preserved material. Some new inf ormative characters, easily observable after fixation, are documented for F ridericia: they concern the distribution of setae in non-bisetose species; the pattern of the clitellum; the structure of the glandular mass in penial bulbs; and lengthwise differentiations of the intestinal wall. The possibi lity that, when further elaborated, some of these features might also shed some light on the intrageneric and intrafamilial relationships is pointed o ut. The crucial importance of details in descriptions of Fridericia and Cer nosvitoviella is highlighted.