A NEW GENUS AND 2 NEW SPECIES OF TUBIFICIDAE (OLIGOCHAETA) FROM THE ABYSSAL ZONE OF LAKE-BAIKAL WITH REDESCRIPTIONS OF LYMPHACHAETA-PINNIGERA, RHYACODRILOIDES ABYSSALIS AND TUBIFEX BAZIKALOVAE

Recent sampling of the abyssal zone of Lake Baikal (Siberia) made poss ible redescriptions of the poorly known species Lymphachaeta pinnigera Snimschikova, Rhyacodriloides abyssalis Chekanovskaya, Tubifex bazika lovae Chekanovskaya, and descriptions of Burchanidrilus petitbonum gen . n., sp. n. and Rhyacodriloides gladiiseta sp. n. Lymphachaeta and Bu rchanidrilus belong to a complex of small Tubificinae, characterised b y true penes in penis sacs, rather simple atria, and lack of coelomocy tes and spermatozeugmata. These mag be considered plesiomorphic charac ter states for Tubificinae. Rhyacodriloides is still assigned to the R hyacodrilinae, despite simple-pointed setae, the lack of coelomocytes, the presence of single genital seta and possible 'multiple' prostates . (C) 1998 The Norwegian Academy of Science and Letters.