Ecological survey of the aquatic oligochaetes in the Lower Pearl River (People's Republic of China)

The species composition, distribution and abundance of the Tubificidae (8 spp.) and Naididae (at least 4 spp.) in the Guangzhou reach of the Lower Pearl River were investigated. Limnodrilus spp. (particularly L. hoffmeisteri) constitutes the greatest part in nearly all samples, which were taken in both clean and polluted parts of the reach. In the polluted sites, total oligochaete densities reach values of up to 700 000 ind. m^–2. The importance and problems of using oligochaetes as indicators of organic pollution are discussed.     

Habitat variability of the Littorelletea uniflorae plant communities in Polish Lobelia lakes

Research was carried out to determine aquatic oligochaete habitat preferences in the Rokytná River (Thaya River basin), a sixth order highland stream in the Czech Republic during the period of April 1999–April 2001. Quantitative samples were collected and current velocity and basic physico-chemical variables were measured monthly in four typical habitats in the Rokytná River. During this study, 28, 842 individuals representing 44 oligochaete species or higher taxa were collected. Temporal variability of proportional occurrence of trophic groups found on selected habitats (gathering collectors and grazers) was analysed. Habitat preferences of oligochaete species were evaluated by Canonical Correspondence Analysis (CANOCO). Biochemical oxygen demand (BOD) and nitrate (NO₃⁻) ion concentration were the most important variables explaining the distribution of Oligochaeta along the first axis. Current velocity (at 40% of the depth) and presence of oligochaetes associated with the habitat where gravel bars never formed were the most important variables along the second axis. Both axes were correlated with the temperature, reflecting the sampling in summer along the first axis and sampling in late spring along the second axis. The amount of organic matter (BOD) and concentrations of NO₃⁻ ions represented both oligochaete food source and decomposition products contributing to the growth of algae. Current velocity and preferred habitat explained the spatial pattern of oligochaete distributions.     

The primary production of phytoplankton in the restored Maltañski Reservoir in Poland

Patterns in composition, abundance and diversity of the annelid fauna (Polychaeta and Oligochaeta) in 22 sandy beaches in Iceland were explored. The effect of exposure on annelid distribution was studied. A total of 5651 annelids were recorded from 160 core samples. Oligochaetes (chiefly Tubificidae) dominated the annelid assemblage whereas polychaetes represented a minor fraction. Polychaetes were relatively more abundant in exposed than in sheltered beaches, contrary to oligochaetes. Meiofaunal polychaete species were also more abundant in exposed than in sheltered beaches. Southwest beaches seemed more diverse in annelid species than northern ones. Annelid diversity did not differ between sheltered and exposed sites, but higher diversity was attained in fine sands at sheltered areas. Cluster analysis revealed large differences between beaches in the annelid community composition. The general patterns found suggest that beach exposure is a major factor conditioning macro- and meiofaunal polychaete and oligochaete distribution along the Icelandic coast.     

Anatomy and ultrastructure of the marine oligochaete Tubificoides benedii (Tubificidae), with emphasis on its epidermis-cuticle-complex

Although Tubificoides benedii (d'Udekem, 1855) (= Peloscolex benedeni) is a ubiquitous form in eutrophicated or polluted coastal muds and is characterized by an exceptional viability in sulphide sediments, almost nothing is known about its anatomy and the structure of its conspicuously papillate body surface. As a part of a research project on sulphide annelids, done by our group, we investigated the body structure of this common and still extraordinary marine tubificid using light, scanning and transmission electron microscopy.While the internal structures correspond to the general pattern of marine tubificids (Giere, 1983), the epidermis-cuticle-complex is unusual. The epidermis cells, which are much interdigitated, contain numerous extremely long and irregularly shaped mitochondria. At the tip of the body, many sensory cells, embedded in the normal epidermis cell layer, end with ciliary tufts at the body surface. Long epidermal microvilli traverse the thick cuticular layer which only in the anterior- and posterior-most segments is studded by epicuticular projections. From most parts of the body these surficial rodlets, so far held typical for all Oligochaeta, are absent. Instead, here the cuticle forms numerous high, almost leaf-life papillae between which a viscous mucus layer regularly harbours many bacteria.This distinct papillate body armature may serve for stabilization of the mucus layer with its associated bacteria. It is well conceivable that the mucus, beside its usual role of reducting friction in the burrowing process, attracts bacteria. That their settlement may be more than an accidental association and involve some regulative interaction is indicated by the specific attachment of gram-negative bacterial threads often populating the posterior end of T. benedii (Dubilier, 1986). The significance of possible stress exerted by the sulfide-environment on the worm, as evidenced by an unusually high concentration of lysosomal structures and abnormally formed mitochondria in the epidermis, has to be verified in further studies.     

Progress in cohort cultures of aquatic Oligochaeta

Our laboratory work on the life cycle of aquatic Oligochaeta has been extended to the tubificids Potamothrix hammoniensis and P. heuscheri, as well as to the lumbriculid Bichaeta sanguinea.Basically we measured the duration of the time required for the embryonic development inside the cocoons, at different temperatures. In addition, cohorts of these species were cultured and the time required to attain the sexual maturation and the cocoon laying stages were estimated.The results concerning these three species are consistent with the field observations, as far as their value as indicator species is concerned, and contribute to a further understanding of the role of biotic factors in determining the distribution and succession of some aquatic Oligochaeta.     

Preliminary report on the Enchytraeidae (Oligochaeta) of West Florida

A wide range of habitats, both terrestrial and marine littoral, were sampled in an area between Pensacola and Tallahassee. Enchytraeids were present in all moist or wet soils and in marine habitats enriched by organic matter but were absent or rare in very dry soils, saturated or flooded substrates and clean intertidal sand. Between 70 and 75 species were distinguished of which 50–55 are new to North America and about 25 are probably new to science. The genera represented are the same as those occurring in Western Europe but their relative importance differs and there are some tropical elements. The number of species occurring in terrestrial sites was greater than recorded in similar surveys in southwestern France and Ireland (approximately the same-sized area, number of sites and size of sample), but the number of species per sample was lower than in either of the other countries. It is concluded that species distribution in western Florida is very patchy. Possible reasons for this patchiness are discussed.     

New species of Phallodrilus (Oligochaeta,Tubificidae) from caves of northern Spain and southwestern France

A taxonomic account of a collection of Phallodrilus species inhabiting caves is given. The following three new species are described: P. subterraneus, P. crypticus and P. labouichensis. New material of P. aquaedulcis Hrabe, 1960 from northern Spain and southwestern France is reported. This species was previously known from West Germany. The relationship between Phallodrilus cave species and littoral and deep-sea species is discussed.     

New chromosome counts in the subtribe Centaureinae (Asteraceae, Cardueae) from West Asia, II

Seventeen chromosome counts of nine species of Centaurea , two species of Serratula , one species each of the genera Aetheopappus, Amberboa, Hyalaea, Oligochaeta, Stizolophus and the type of the monospecific genus Callicephalus from Armenia are reported; three of them are new reports, four others are corrections of previous counts and ten are confirmations of very scarce previous data.     

Some fresh-water oligochaeta of Nagpur,India

The paper records the occurrence of 23 species of fresh-water oligochaetes belonging to five families collected in and around Nagpur City. Of these, Nais andina Cernosvitov is a new record for the Indian sub-continent and for the eastern hemisphere. Its sex organs are described for the first time here. Aulophorus moghei is new to science. Sixteen other species, Nais andina and Aulophorus moghei are planktonic forms and the rest inhabit mud at the bottom of water sources.