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

Abstract

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 characterized by large, coarsely granular coelomocytes, small spermathecae confined to V, sperm funnels funnel-shaped and sperm ducts ectally swollen and stiffened. Fridericia christeri sp. n. is distinguished by its constant lack of spermathecae (confirmed by observations in laboratory cultures), a bisetose condition of all its postclitellar lateral bundles, and the regular arrangement of its clitellar cells; this species also lives in the island of Öland in the Baltic sea. Fridericia ulrikae sp. n. has thinwalled, cylindrical spermathecal ampullae with stalked, sharply bent diverticula, and large penial bulbs, with ‘redundant’ glandular tissue flanking the basic cushion. Fridericia waldenstroemi sp. n. is characterized by its peripherally granular coelomocytes, the preclitellar location of its chylus cells, and the two-tone glandular cover of its sperm funnels. Another twelve species (Cernosvitoviella minor, Enchytraeus bulbosus, E. lacteus, Fridericia callosa, F. gracilis, F. isseli, F. leydigi, F. paranemoralis, F. singula, Hemifridericia 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 species diagnoses and helping identification of preserved material. Some new informative characters, easily observable after fixation, are documented for Fridericia: 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 possibility that, when further elaborated, some of these features might also shed some light on the intrageneric and intrafamilial relationships is pointed out. The crucial importance of details in descriptions of Fridericia and Cernosvitoviella is highlighted.