MORPHOLOGY AND ADAPTATIONS OF PARERGODRILUS REISINGER AND HRABEIELLA PIZL AND CHALUPSKY, 2 ENIGMATIC SOIL-DWELLING ANNELIDS

Parergodrilus heideri Reisinger, 1925 and Hrabeiella periglandulata Pi zl & Chalupsky, 1984 s. l. are the only two non-clitellate annelids wh ich permanently inhabit the litter and humic layers of land soils in t emperate climates. Their minute body size and difficulty of extraction from the substrate account for their late discovery and subsequent sc anty records. Both taxa are European. Although they widely overlap in geographic and ecological distribution, they appear only remotely rela ted. Neither Parergodrilus nor Hrabeiella displays more than a superfi cial resemblance to the families formerly included in the 'archianneli ds'. Since 1960 Parergodrilus has been classified with the marine inte rstitial Stygocapitella subterranea Knollner, 1934 in the family Parer godrilidae, possibly related to some other interstitial forms or to de posit feeders of mobile bottoms. The position of Hrabeiella appears mo re obscure, yet very interesting in view of the many convergences (con cerning the organization of the body wall musculature, pharynx, male t erminalia, spermatozoal morphology) with the oligochaetes.