The occurrence of species of semi-aquatic Enchytraeidae (Oligochaeta) in Ireland

The Enchytraeidae are essentially terrestrial oligochaetes but many species have marked aquatic tendencies. Over two thirds of recorded Irish species were found in soils which were submerged or frequently flooded and 35% showed a distinct preference for these conditions. Relatively few species were living in soils subject to drought. Red blood was present in 28 species, all but one from soils with more than 55% water. Cognettia sphagnetorum and C. glandulosa developed red blood in very wet conditions. In a survey of Irish wetlands, samples were taken from bog, heath, marsh, fen, margins of lakes and rivers, and saltmarsh. The influence of various environmental parameters was determined using ordination techniques. Magnesium and pH were found to be the most important factors. A high level of magnesium distinguished coastal sites and pH 5.2 separated two clusters representing acid peat and marsh-fen-aquatic sites. Groups of indicator species characterized each of the three clusters. The ecological distribution of the indicator species is described, and their usefulness in classifying enchytraeid communities is discussed.     

Specific criteria in Grania (Oligochaeta,Enchytraeidae)

The structure of the penial bulb and male efferent duct system of Grania species may be used in addition to setal pattern and spermathecal shape to distinguish species. Six penial bulb types are distinguished: (1) a simple, small, glandular bulb surrounding the male pore; (2) a small, glandular bulb, with a large, associated, dorso-medial gland mass; (3) a small glandular bulb, medial to the male pore, with an elongate male bursa (the aglandular sac), the vas deferens exitting directly into the invaginated male pore; (4) a glandular bulb with an aglandular sac and a small, cuticular stylet embedded in the bulb, extending from the ectal end of the vas deferens; (5) a glandular bulb and an aglandular sac with a long stylet extending from the vas deferens, through the bulb into the sac; and (6) glandular bulb reduced or absent, with or without an aglandular sac; with a long stylet and other prominent modifications, usually muscular, of the vas deferens. The details of the male duct structure were consistent within specimens grouped on the basis of setal distribution and shape and detailed spermathecal structure. Diverse male duct patterns are found within the polytypic species G. macrochaeta and G. postclitellochaeta. The positions of the spermathecal and male pores in their respective segments are distinctive for some species.     

Molecular phylogeny of Enchytraeidae (Oligochaeta) indicates separate invasions of the terrestrial environment

Enchytraeidae is a family of soil inhabiting small‐ to medium‐sized oligochaete worms using degradable plant material as a food source and primarily adapted to terrestrial or semi‐terrestrial environments. The molecular phylogeny based upon both mitochondrial and nuclear genes indicates early segregations of the two genera Enchytraeus and Lumbricillus leaving the remaining genera included in this study as a later segregated major monophyletic branch. Extant members of the two former genera dominate in decaying seaweed in the littoral zone along the sea although members of in particular the genus Enchytraeus have also invaded other habitats. Historically the littoral zone of the sea is undoubtedly the first terrestrial or semi‐terrestrial habitat where dead plant material accumulates to any greater extent and Enchytraeus and Lumbricillus may represent early successful attempts to exploit this resource. Inland soils probably had to await the emergence of land plants in order to provide a similar food resource and here the major branch of enchytraeid genera diversified into a high number of species in the numerous decomposer networks of this varied environment. A subdivision into the genera Enchytraeus and Lumbricillus on the one hand and a branch of mainly inland genera on the other is supported by differences in two somewhat neglected morphological features. Firstly, in Enchytraeus and Lumbricillus the testes are enclosed in a testis sac within which the male cells mature, by one possible exception a unique feature among Oligochaeta, The other enchytraeid genera studied and Oligochaeta in general lack this sac and the male cells mature directly in the cavity of the testicular segment. Secondly, species of Enchytraeus and Lumbricillus generally have a higher reproductive output than species of the inland terrestrial branch and this may represent an adaptation to the unpredictable littoral zone compared to the more stable nature of inland habitats. In the older literature the genus Mesenchytraeus is considered to have a basic position within the entire family but our molecular data do not support this expectation. In Enchytraeidae the nephridia are elaborate organs of a characteristic and constant shape covering species from different genera in a pattern following the molecular phylogeny. Other much used morphological features such as shape of setae, anteclitellar origin of the dorsal vessel and various modifications of the intestine have arisen more than once.     

A taxonomic and faunistic survey of the marine Tubificidae and Enchytraeidae (Oligochaeta) of Italy. Introduction and preliminary results

On the basis of material collected along the Ligurian, Tyrrhenian, Ionic and Adriatic coasts of Italy, a tentative list of 26 species (18 tubificids, 8 enchytraeids) of marine Oligochaeta is presented. Most of the species are new to science, and it can therefore be concluded that there is a very high diversity of oligochaetes in the Mediterranean Sea.     

Species separation and identification in the Enchytraeidae (Oligochaeta, Annelida): combining morphology with general protein data

In the Enchytraeidae, species separation and identification is often problematic due to high morphological similarity of closely related species and considerable intraspecific variability of crucial characteristics. Immature specimens are almost undeterminable. To meet these difficulties, this paper recommends the consulting of general protein patterns as exhibited by non-specific silver-staining after isoelectric focusing. A method is presented which allows the successful inclusion of protein data in taxonomic studies and field surveys. Two examples from an investigation on Fridericia field populations show that, with the help of general protein pattern analysis, a clear taxonomic decision on the identity of morphologically aberrant forms and of juvenile specimens as well can be achieved with comparatively little expenditure of time. A combined use of morphological and protein data for taxonomic purposes is suggested.     

Preliminary investigations of hybridization/reticulate evolution in Guaranidrilus (Enchytraeidae: Oligochaeta)

The identification of gut diverticula at 7/8 as a synapomorphy and recognition of all taxa of Guaranidrilus has been obscured by losses of gut diverticula within the lineage. The homoplastic occurrence of basally unpaired peptonephridia in some enchytraeid species has similarly obscured the limits of Hemienchytraeus. Taxa with unpredictable relationships, morphogenic irregularities in some reproductive structures, and, apparently, modified modes of reproduction, suggest the possibilities of hybridization between taxa with both close and distant relationships.     

Propappidae and aquatic Enchytraeidae (Oligochaeta) from the farthest southeast of Russia

Two mountain streams north and northeast of Vladivostok were studied in 1983–1984. In the Komarovka Stream, a great variety of Mesenchytraeus occurred in the spring zone, among them M. crenobius sp. n. with giant setae in the ventral bundles of VI–VIII and M. vshivkovae sp. n. with numerous spermathecal diverticula. In the stream zone of the Frolovka Stream Cernosvitoviella pensau sp. n., characterized by a complicated penial bulb and a very long spermathecal ampulla, was the dominant oligochaete. Propappus arhynchotus Sokolskaya was the second most abundant oligochaete in this stream. It proved to be a true member of this genus and not synonymous with any other species. These are the first records of aquatic enchytraeids for the Primorski Region of Russia.     

Bioaccumulation of lindane and hexachlorobenzene by the oligochaetes Enchytraeus luxuriosus and Enchytraeus albidus (Enchytraeidae,Oligochaeta, Annelida)

The uptake of chemicals in soil organisms, especially earthworms, has been studied many times. However, in Europe no internationally accepted standardised test guideline for the assessment of bioaccumulation in the soil ecosystem exists. Therefore, the German Federal Environmental Agency recently funded a project in which a standardisable test method for measuring bioaccumulation of chemicals using earthworms and enchytraeids is being developed. In this contribution, initial results with the new method are presented, using two model chemicals (the insecticide lindane and the fungicide hexachlorobenzene). Two enchytraeid species (Enchytraeus luxuriosus and Enchytraeus albidus) were selected as test organisms due to their easy handling and their important ecological role in the soil compartment. Artificial soil and a natural standard soil were used as test substrates. Test concentrations were based on previous results of acute and reproduction toxicity tests performed with the same species. Uptake as well as the elimination of the test substances were examined under standardised conditions in a closed test system. The first results show that both chemicals were accumulated considerably by both enchytraeid species. The bioaccumulation factors (BAFs) of lindane and hexachlorobenzene found for enchytraeids are significantly higher compared to those for lumbricid earthworms. Evaluation of the preliminary data suggests that the smaller species E. luxuriosus accumulated the two chemicals to a greater extent than E. albidus. In most cases, both chemicals were eliminated completely. The use of this new test method appears suitable for the ecotoxicological risk assessment of bioaccumulative chemicals.     

Phylogenetics of some Enchytraeidae (Annelida: Oligochaeta): A preliminary investigation of relationships to the Haplotaxidae

In phylogenetic considerations of the Oligochaeta and the family Enchytraeidae, Propappus has been considered the ancestral or even the archetypal enchytraeid genus. Three nominal species are presently included in Propappus Michaelsen, 1905, P. volki Michaelsen, 1916, P. arhyncotus Sokolskaja, 1972, and the type species of the genus, P. glandulosus Michaelsen, 1905. Examination of type material of P. glandulosus and P. volki, as well as other material of the latter, showed that these species have a single pair of testes in segment XI and a single pair of ovaries in segment XIII. According to current classifications of the Oligochaeta, these species of Propappus cannot be retained in the Enchytraeidae. A phylogenetic analysis including two species of Propappus and 29 species of Haplotaxidae suggest a sister group relationship between Propappus and some Enchytraeidae and Haplotaxidae.     

Population dynamics and functional roles of Enchytraeidae (Oligochaeta) in hardwood forest and agricultural ecosystems

Population dynamics of enchytraeids are described for 2 montane forested watersheds in southwestern North Carolina (Coweeta) and an agricultural site under conventional (CT) and no-tillage (NT) management in the northeastern Georgia piedmont (Horseshoe Bend, HSB). Given that much of the taxonomy, ecology and community structure of enchytraeids is poorly known, our objective was to identify key indicators of enchytraeid community structure which could be used, in this case, to better understand their role in soil structure formation. Although population densities of enchytraeids were higher in the forested (Coweeta) than in the arable soils (HSB), the average ash free dry weight per enchytraeid at HSB was nearly double that found at Coweeta. Based on these measurements and an estimate of their gut transit time, we calculated that the enchytraeids at HSB transported 2180 g of soil per m² per year compared to 443 and 393 g m^-2 yr^-1 for watershed 18 and 27, respectively at Coweeta. We therefore hypothesize that enchytraeids have a larger influence on soil structure in agricultural fields than in forested areas, in spite of lower population densities. The ash free dry weight and ash wt. per enchytraeid may qualify as key indicator parameters of enchytraeid community structure which helps to understand their functional role in ecosystems, though more studies are called for.     

Preliminary study of the aquatic Oligochaeta of the Changjiang (Yangtze) River

The aquatic oligochaetes in mainstream of the Changjiang River have not been studied previously. Since 1983, benthic samples have been collected mainly from mid-upper reach of the river. Altogether 19 species belonging to 4 families of the Oligochaeta were found. Among them, Nais inflata is the commonest species throughout the river, whereas Nais sp., Arcteonais lomondi, Limnodrilus silvani, Rhyacodrilus riabuschinskii and Telmatodrilus sp. ae recorded from China for the first time.Quantitatively, the aquatic oligochaetes constitute the majority of zoobenthos in the mainstream. In 1984, the standing crop of the Tubificidae was 231–343 ind·m^-2 in density and 0.73–0.97 g·m^-2 (wet weight) in biomass, and that of the Naididae was 21–4982 ind·m^-2 and 0.003–1.75 g·m^-2 (wet weight) respectively.     

Cryptic diversity among the achaetous Marionina (Annelida,Clitellata, Enchytraeidae)

This study investigates the diversity and taxonomy of a mainly marine group of species lacking chaetae currently assigned to the genus Marionina. This achaetous group includes four nominal species: M. achaeta (Hagen, 1954 Hagen, G. 1954. Michaelsena achaeta nov. sp., ein neuer mariner Oligochaet aus der Kieler Bucht. Faunistische Mitteilungen aus Norddeutschland, 1: 12–13.  [Google Scholar]), M. achaeta sensu Lasserre, 1964 Lasserre, P. 1964. Notes sur quelques oligochètes Enchytraeidae présents dans les plages du Bassin d’Arcachon. Procés-Verbaux des Séances de la Société Linnéenne de Bordeaux, 101: 87–91.  [Google Scholar], M. nevisensis Righi & Kanner, 1979 Righi, G. and Kanner, E. 1979. Marine Oligochaeta (Tubificidae and Enchytraeidae) from the Caribbean Sea. Studies of the Fauna of Curaçao and other Caribbean Islands, 58: 44–68.  [Google Scholar] and M. arenaria Healy, 1979 Healy, B. 1979a. Marine fauna of County Wexford. 1 – Littoral and brackishwater Oligochaeta. The Irish Naturalists' Journal, 19: 418–422.  [Google Scholar]. As Lasserre's (1964 Lasserre, P. 1964. Notes sur quelques oligochètes Enchytraeidae présents dans les plages du Bassin d’Arcachon. Procés-Verbaux des Séances de la Société Linnéenne de Bordeaux, 101: 87–91.  [Google Scholar]) M. achaeta appears to be morphologically different from its (then) senior homonym M. achaeta (Hagen, 1954 Hagen, G. 1954. Michaelsena achaeta nov. sp., ein neuer mariner Oligochaet aus der Kieler Bucht. Faunistische Mitteilungen aus Norddeutschland, 1: 12–13.  [Google Scholar]), the replacement name M. nothachaeta nom. nov. is proposed for it. We studied the genetic and morphological diversity of achaetous specimens of Marionina collected in Florida, the Great Barrier Reef, New Caledonia, Sweden, England and the Bahamas. The collection localities are almost all supralittoral and often brackish-water habitats. Parts of the mitochondrial genes 12S, 16S, COI and the nuclear genes 18S, 28S and ITS were analysed to assess the genetic variation and phylogeny of the achaetous Marionina species. The molecular data reveal one monophyletic group of 11 separately evolving lineages, and between these lineages, K2P distances in the barcoding gene COI vary between 5.4 and 25.0%. On a morphological basis, the lineages could be assigned to seven different groups (morphotypes), of which only two could be identified as described nominal taxa: M. nevisensis s. lat. (several lineages) and M. nothachaeta. Since the former taxon appears to be a complex of cryptic species around the world and the original type material no longer exists, a neotype from the Caribbean was designated for M. nevisensis s. str. The remaining achaetous lineages represent five morphologically distinct species that are left unnamed, awaiting finer morphological scrutiny and detailed comparisons with new collections of M. achaeta and M. arenaria. Summing up, the group of achaetous Marionina now seems to contain up to 13 different species, seven of which are yet to be formally described and named.     

Sublittoral and profundal Oligochaeta fauna of the Lake Constance (Bodensee-Obersee)

Fourteen tubificid species and one lumbriculid make up the oligochaete population of the northern half of Lake Constance, a meso- to mesoeutrophic lake. Tubifex tubifex makes up 72% of the total abundance, the clean water species Stylodrilus heringianus only 0.1%. No correlation exists between total worm abundance and organic carbon content of the sediment, only 4% of the organic carbon being used by the worms. A highly significant correlation between particulate organic matter loading and its organic carbon content from 10 tributaries and total oligochaete abundance is demonstrated. The ecological index I_PA is defined and used to assess the biologically relevant trophic status of the lake bed. This integrates information on the percent representation of three groups of worm species classified on atrophic basis and total abundance of the worms. Despite control of the increase in phosphorus loadings progressive eutrophication of sediments was observed after an 8 year interval.     

Population dynamics and energy budget of Marionina southerni (Cernosvitov) (Enchytraeidae,Oligochaeta) in the shallow littoral of Lake Esrom,Denmark

Marionina southerni (Cernosvitov) was numerically the dominant oligochaete in a shallow, strongly exposed surf zone locality (0–1 m depth) in the mesotrophic Lake Esrom. It comprised 21,500 ind m^–2 or nearly 50% of the total oligochaete community, which otherwise was dominated by Nais spp. and the lumbriculid Stylodrilus heringianus Claparède. M. southerni appears to have a 1-y life cycle. Individual biomass ranged from 3 to 48 µg ash free dry weight. Annual net production at the site was 5.1 kcal m^–2 (size-frequency method) with a P/B ratio of 2.5. This is about 0.5% of the estimated mean zoobenthic production in the littoral zone from 0 to 2 m depth in Lake Esrom. At 5° C M. southerni showed a constant oxygen uptake down to 25% oxygen saturation, but practically no regulatory respiration was found at 20 °C. In the field M. southerni was never found in sediment with less than 60% oxygen saturation. The annual community respiration of M. southerni was 14.2 kcal m^–2, and annual assimilation thus made up 19.3 kcal m^–2 with a net production efficiency of 26.5%.     

The geographical distribution of Naididae (Oligochaeta) in Britain

A compilation of records of the geographical location of naidid species in Britain is presented. Many species previously considered rare are shown to be widely distributed.     

Pygidialporen bei marinen Enchytraeidae (Oligochaeta)

Coelo-rectal pygidial pores were found in the anal area of marine enchytraeids (Lumbricillus lineatus, Marionina spicula, Enchytraeus albidus) from the mud-flats of the Isle of Sylt. The structure and function of these pores have been discussed.     

Oligochaetes (Naididae, Tubificidae, Opistocystidae, Enchytraeidae, Sparganophilidae and Alluroididae) of Guyana

About 50 species in more than 20 genera of the microdrile oligochaete families Tubificidae, Naididae, Opistocystidae, and Enchytraeidae and the freshwater megadrile families Sparganophilidae and Alluroididae were identified in recent collections made in Guyana. Only seven species in these families were previously recorded from Guyana. The aquatic oligochaete fauna has similar components to those of the southeastern United States, other locations in South America, and across lower latitudes in the northern hemisphere. A high diversity of species is found in the naidids especially in the genera Pristina and Pristinella, especially considering the small number of locations that have been sampled. The collections include approximately 12 new species of rhyacodrilines (Tubificidae), Dero, Pristina, Pristinella (Naididae), Brinkhurstia (Alluroididae), Hemienchytraeus and Aspidodrilus (Enchytraeidae). This is the first record of Aspidodrilus from outside of Africa and the first new record since 1952.     

The spatial pattern of Enchytraeidae (Oligochaeta)

Summary Spatial pattern of enchytraeids (Oligochaeta: Enchytraeidae) was studied in an experimental plot in an apple orchard near Bavorov, South Bohemia, Czechoslovakia. A total of 450 soil cores were taken in 1982, all individuals were determined (juveniles to genus, mature individuals to species) and counted. In total, 17 species of 4 genera were found. Both juveniles and mature individuals exhibited a distinctly aggregated spatial pattern. The distribution of the number of individuals in a sampling unit may be effectively fitted by the negative binomial distribution. The fit of Neyman type A distribution was considerably poorer. Comparing juveniles and mature individuals of the same genus using Lloyd's index of patchiness we found mature individuals to be slightly more aggregated than juveniles. Comparing the observed distribution of species number with that expected under the assumption of independence we may conclude that individuals appear in multispecies aggregation centres. These two conclusions support the hypothesis that aggregations are environmentally conditioned (abiotic factors and/or food availability) rather than caused by the type of reproduction.