We investigated benthic macroinvertebrate communities in three contrasting habitats of a large shallow lake from February to November 2009. The three habitats differed markedly in their environmental characteristics (e.g., trophic status, substrate type, wind exposure). A total of 36 species were collected from the three habitats. The calculated descriptors (abundance, biomass and Pielou evenness index) differed significantly among the habitats. Generally, Tubificidae, Bivalvia and Gastropoda dominated the benthic community in abundance and biomass, but they varied greatly in abundance among the habitats. Analysis of similarities (ANOSIM) and non-metric multidimensional scaling (NMDS) analyses revealed significantly different macroinvertebrate assemblages among the habitats. North Bays had the lowest biodiversity and were exclusively dominated by pollution-tolerant species (e.g., Limnodrilus hoffmeisteri and Rhyacodrilus sinicus). Communities in the open lake contained intermediate biodiversity and were characterized by five species belonging to several taxonomic groups (e.g., Corbicula fluminea, L. hoffmeisteri and Gammarus sp.). Macrophyte-dominated habitats (East Bays) presented the highest diversity and evenness and were mainly characterized by gastropods. A canonical correspondence analysis (CCA) demonstrated that habitat-specific differences in trophic status, pollution level, wind-induced disturbance and macrophyte distributions were highly correlated with macroinvertebrate community structure.

The development of the male duct and spermatheca is studied in three species of the marine Limnodriloidinae (Tubificidae): Limnodriloides rubicundus; Tectidrilus bori; Thalassodrilides ineri. All tubificids are hermaphroditic with paired male ducts, female ducts and, as a rule, spermathecae. The male duct comprises a funnel, followed by a vas deferens, an atrium and, frequently, a copulatory structure. There may also be a diffuse or compact prostate gland in association with the male duct. In the three species studied, the funnel and vas deferens originate from peritoneal (mesodermal) cells in the posterior septa of the testes segment. The atrium develops from an invagination of the epidermis (ectoderm). The vas deferens and atrium subsequently connect to each other, and a continuous duct from the testes segment to the exterior is formed. The prostate gland originates from large peritoneal cells occurring in a delimited area on the outer surface of the atrium; other small peritoneal cells surrounding the whole atrium give rise to muscle fibres. The spermatheca develops from an invagination of the epidermis, and is thus of ectodermal origin. The morphology and position of the genital ducts have been and are important for the classification of the oligochaetes. However, different parts of the male duct have been named without regard to whether they are homologous or not. One way to establish stronger primary hypotheses of homology is to study the detailed morphology and/or the development of the genital ducts.

Two features have been considered apomorphic for the subfamily Limnodriloidinae (Tubificidae): the lobed prostate glands, which are broadly attached to prostatic pads inside the atrial ampullae, and the ‘modified oesophagus’ in segment IX. The homology of the modified oesophagus may be questioned, as it is not of the same kind in all taxa. In Limnodriloides, Smithsonidrilus, and Tectidrilus, there is a pair of diverticula, whereas in Thalassodrilides, Parakaketio, and Doliodrilus, the oesophagus is dilated to form a barrel-shaped portion. In a few species of Limnodriloides lacking diverticula, a short part of the corresponding oesophagus is swollen. A scrutiny of these features shows that they are morphologically different in several aspects: the thickness and the structure of the epithelium, the granulation, the shape of the cells and the length of the modifications. Moreover, a regular, semi-embedded blood plexus always occurs around the barrel-shaped portion but rarely around the diverticula (if present, plexus irregular), and never around the swollen part of the oesophagus. These different types of modifications fail the similarity test and thus should be regarded as independently evolved structures and coded as different characters in a parsimony analysis. Species from other subfamilies within the Tubificidae were also morphologically investigated, and modifications of the alimentary canal were found in a few of them: Ainudrilus lutulentus, Heronidrilus bihamis, H. fastigatus (all Rhyacodrilinae) and Clitellio arenarius (Tubificinae). The modification in segment VIII of Heronidrilus spp. resembles the barrel-shaped portion in, for example, Thalassodrilides, and should primarily be coded as the same character in a congruence test of homology.

Many Oligochaeta were collected during recent investigations in Southern-European caves. This is the first contribution in which some data concerning the Tubificidae are summarized. Three new species of Rhyacodrilinae, including a new genus, are described: Rhyacodrilus omodeoi n. sp., Rhyacodrilus dolcei n. sp., Rhyacodrilus gasparoi n. sp. and Stochidrilus glandulosus n. gen., n. sp. The poorly known species Frearidrilus pescei (Dumnicka 1981, augm. 1987) is redescribed on the basis of new material collected in Slovenian caves; this revision allowed the proposal to ascribe it to the genus Tubifex, considering the monospecific genus Frearidrilus as a junior synonym of Tubifex.