Oligochaete distribution patterns in two German hardwater lakes of different trophic state

AbstractWe investigated the effect of contrasting trophic conditions on the distribution and dominance patterns of Oligochaeta species assemblages in lake sediments and their relation to the environmental variables depth, season, and substrate. The study was performed on the highly eutrophic Lake Haussee and the oligotrophic Lake Stechlin, both hardwater lakes in the Baltic Lake District of Northern Germany. Quantitative monthly and seasonal sampling took place over one year at 14 representative sites, covering littoral and profundal sediments of both lakes. Between-lake differences in the profundal were clearcut with an absence of any zoobenthos in Lake Haussee and a peculiar meiobenthic species assemblage in Lake Stechlin (Collado et al. 1999). Between-lake differences in the littoral, however, were small and mainly attributable to a small number of species exclusive to Lake Stechlin and an overall higher abundance of oligochaetes, especially naidids, in Lake Haussee. Species-richest family in both lakes were Naididae; Tubificidae were dominant in Lake Stechlin; in Lake Haussee Tubificidae and Naididae were equally abundant. Most striking were diversity of habitat types and species distribution patterns in the littoral. Multivariate analysis (CA, CCA) showed that the distribution patterns of oligochaete species assemblages are significantly correlated with depth, season and substrate. Depth is the major factor when the whole water body is considered. When confining to the littoral, species abundance and distribution are strongly related to seasonality and substrate type. Naididae show, in general, maximal abundances in autumn and summer and a preference for plants, plant debris and soft sediments; Tubificidae are more abundant in spring and prefer mineral substrate. The relation between seasonality, substrate and food availability is discussed

Description of Enchytronia pygmaea sp. n. (Enchytraeidae, Clitellata), a very small enchytraeid in European soils

A new and very small European species of terrestrial enchytraeids is described, Enchytronia pygmaea sp. nov. (Enchytraeidae, Oligochaeta). It differs from all enchytraeids known so far in the chaetal pattern: lateral bundles have 2 chaetae from segment II to V, 0 from segment VI to XII–XV, and only 1 chaeta in lateral postclitellar bundles; ventral bundles have 2 chaetae. A further peculiarity is the presence of only 1 pair of preclitellar nephridia. The species must be considered as widespread as it is recorded here from 17 different localities distributed over seven European countries ranging from the Atlantic to the Mediterranean zone

On a collection of enchytraeids (Oligochaeta) from first order streams in São Paulo State, Brazil

A collection of 21 ethanol-preserved specimens of enchytraeids collected in first order streams in São Paulo State, Brazil, was whole-mounted on slides and investigated under light microscope. Eight species taxa were distinguished, belonging to Achaeta, Guaranidrilus, and Marionina. Five species could be named, one of them tentatively: Achaeta neotropica Černosvitov, 1937, Achaeta singularis Schmelz, 2008, Guaranidrilus oiepe Righi, 1974, Marionina argentea (Michaelsen, 1889) s.l., Marionina cf. seminuda Xie & Rota, 2001. Three further unnamed species taxa of Guaranidrilus were distinguished; two of them may be new species. The presence of sexually mature specimens of A. singularis allowed an emendation of the original description which was based on juvenile specimens. The rod-shaped crystals in the coelom of A. singularis are similar to raphides in plants and sponges, an

Effects of organic pesticides on enchytraeids (Oligochaeta) in agroecosystems: laboratory and higher-tier tests

Enchytraeidae (Oligochaeta, Annelida) are often considered to be typical forestliving organisms, but they are regularly found in agroecosystems of the temperate regions of the world. Although less known than their larger relatives, the earthworms, these saprophagous organisms play similar roles in agricultural soils (but at a smaller scale), e.g., influencing soil structure and organic matter dynamics via microbial communities, and having a central place in soil food webs. Their diversity is rarely studied or often underestimated due to difficulties in distinguishing the species. New genetic techniques reveal that even in anthropogenically highly influenced soils, more than 10 species per site can be found. Because of their close contact with the soil pore water, a high ingestion rate and a thin cuticle, they often react very sensitively to a broad range of pesticides. Firstly we provide a short overview of the diversity and abundance of enchytraeid communities in agroecosystems. Afterwards, we explore the available data on enchytraeid sensitivity toward pesticides at different levels of biological organization, focusing on pesticides used in (mainly) European agroecosystems. Starting with non-standardized studies on the effects of pesticides on the sub-individual level, we compile the results of standard laboratory tests performed following OECD and ISO guidelines as well as those of higher-tier studies (i.e., semi-field and field tests). The number of comparable test data is still limited, because tests with enchytraeids are not a regulatory requirement in the European Union. While focusing on the effects of pesticides, attention is also given to their interactions with environmental stressors (e.g., climate change). In conclusion, we recommend to increase the use of enchytraeids in pesticide risk assessment because of their diversity and functional importance as well as their increasingly simplified use in (mostly standardized) tests at all levels of biological organization

A proposed order-level classification in Oligochaeta (Annelida, Clitellata)

The purpose of our contribution is to propose a robust and practical order-level classification of the families of Oligochaeta, that is, non-leech Clitellata. The order level is mandatory in Linnaean rank-based classification and is also required in many internet-based biodiversity databases. However, it has received little attention in oligochaete systematics, and the few available order-level classifications of Oligochaeta no longer represent phylogenetic relationships adequately. Our proposal is based on corroborated molecular phylogenetic evidence and takes as benchmarks class level for Clitellata, subclass level for Oligochaeta and Hirudinea, and order level for Crassiclitellata, the monophylum that includes most of the earthworm taxa. As a result, eleven orders are proposed: A lluroididA Timm & Martin, 2015; CApilloventridA Timm, n. ordo; CrAssiClitellAtA Jamieson, 1988; enChytrAeidA Kasprzak, 1984; hAplotAxidA Brinkhurst & Jamieson, 1971; lumbriCulidA Brinkhurst & Jamieson, 1971; moniligAstridA Brinkhurst & Jamieson, 1971; nArApidA Timm, n. ordo; pArvidrilidA Timm, n. ordo; rAndiellidA Jamieson, 1988; tubifiCidA Jamieson, 1978. This order-level classification is robust and easily adaptable to future insights into phylogenetic relationships

Effects of Organic Pesticides on Enchytraeids (Oligochaeta) in Agroecosystems: Laboratory and Higher-Tier Tests

Enchytraeidae (Oligochaeta, Annelida) are often considered to be typical forestliving organisms, but they are regularly found in agroecosystems of the temperate regions of the world. Although less known than their larger relatives, the earthworms, these saprophagous organisms play similar roles in agricultural soils (but at a smaller scale), e.g., influencing soil structure and organic matter dynamics via microbial communities, and having a central place in soil food webs. Their diversity is rarely studied or often underestimated due to difficulties in distinguishing the species. New genetic techniques reveal that even in anthropogenically highly influenced soils, more than 10 species per site can be found. Because of their close contact with the soil pore water, a high ingestion rate and a thin cuticle, they often react very sensitively to a broad range of pesticides. Firstly we provide a short overview of the diversity and abundance of enchytraeid communities in agroecosystems. Afterwards, we explore the available data on enchytraeid sensitivity toward pesticides at different levels of biological organization, focusing on pesticides used in (mainly) European agroecosystems. Starting with non-standardized studies on the effects of pesticides on the sub-individual level, we compile the results of standard laboratory tests performed following OECD and ISO guidelines as well as those of higher-tier studies (i.e., semi-field and field tests). The number of comparable test data is still limited, because tests with enchytraeids are not a regulatory requirement in the European Union. While focusing on the effects of pesticides, attention is also given to their interactions with environmental stressors (e.g., climate change). In conclusion, we recommend to increase the use of enchytraeids in pesticide risk assessment because of their diversity and functional importance as well as their increasingly simplified use in (mostly standardized) tests at all levels of biological organization

Fridericia sousai Schmelz & Collado, 2013, sp. nov.

Fridericia sousai sp. nov. (Figs 1 A–C, 5 A, Table 3) Holotype. MNHML MB 29 -000297, adult spcm, stained whole mount. Portugal, Coimbra, in soil from the experimental field area of the Coimbra Higher School of Agriculture (ESAC), meadow site (Table 2); II 2012. Paratypes. Eight spms. MNHML MB 29 -000298 – 301, stained whole mounts: 3 adults, 1 juvenile. ZMH OL 14518, fixed in Bouin's fluid, preserved in 70 % ethanol: 1 adult, 1 juvenile. ZMH OL 14519, fixed in 70 % ethanol, preserved in 100 % ethanol: 2 spms. Other material. 7 spms, investigated in vivo, preserved in collective sample vials, in the authors' collection. Etymology. Named in honour of Paulo Sousa, soil zoologist, ecologist and ecotoxicologist at the University of Coimbra, research director of the TME experiments. Diagnosis. Length <10 mm, less than 40 segments, max. 4 chaetae per bundle, often 3 chaetae per bundle, of same size in a bundle, clitellum girdle-shaped, present also between bursal slits, coelomo-mucocytes with refractile vesicles, nephridia absent at 10 / 11, chylus cells preclitellar with cell canals widened to lacunae, no seminal vesicle, sperm heads 20–25 μm, sperm funnel small, spermathecae separate entally, small ectal gland, two sessile diverticula without ciliated subchamber. Description. Small Fridericia worms. Length 6–8 mm (viv), 4.5–6 mm (fix); diameter 0.15 mm (viv), 0.16 mm (fix), 0.2 mm at clitellum. Segment number 30–35. Chaetae max. 4 per bundle. Formula 2,3, 4 – 4,3, 2: 2,3, 4 – 4,3, 2. In preclitellar bundles mostly 4 chaetae, in postclitellar bundles 4 and 3 chaetae, more 3 than 4 in many specimens; two chaetae only in II and in the hindmost 1 or 2 segments. Anteriorly inner chaetae almost as large as outer, posteriorly all chaetae in a bundle of same size. Posterior chaetae slightly larger than anterior (52–55: 3–3.5 μm and c. 30–40: 2–3 μm, respectively). Chaetae increasing in size from II to VII (from c. 30 μm to c. 45 μm); chaetae in segments following clitellum as large as preclitellar; caudal chaetae largest (up to 60: 4 μm). Epidermal gland cells one row per segment, at chaetal level, few cells, one each dorsally of lateral chaetae. Body wall c. 15 μm thick, longitudinal muscle layer comparatively thin, 1–1.5 x as thick as layer of ring muscles plus epidermis, cuticle very thin, barely visible at 400 x magnification, estimated thickness <0.5 μm. Body surface slightly wavy in about 10 transverse rows per segment. All septa thin. Brain rounded posteriorly, 80: 50 μm, sides almost parallel, anteriorly slightly convex, almost truncate. Pharyngeal glands dorsally connected in IV, V, separate in VI. Dorsal lobes all of same size, ventral lobes of same size in V and VI, small in IV. Oesophageal appendages short, unbranched. Chylus cells in IX–X, canals widened into elongate lacunae. Intestine widened in chylus region. Dorsal blood vessel from XIII. Midgut pars tumida from XX–XXIV, occupying 3–3.5 segments lengths. Preclitellar nephridia 4 pairs, from 6 / 7 to 9 / 10, length ratio anteseptale: postseptale about 1: 2; adseptal to medial rise of efferent duct, no terminal vesicle; postclitellar nephridia sparse, often unpaired, first from c. 17 / 18, shape as preclitellar, terminal rise of efferent duct. Coelomomucocytes with small refractile vesicles at periphery, cell length 15–20 μm, matrix almost hyaline (viv); lenticytes numerous but inconspicuous (viv), length 5–6 μm, i.e. about 1 / 3 of mucocyte length. Clitellum girdle-shaped, cells in c. 25 dense rows, flat (i.e. cells wider than high), conspicuous in vivo, inconspicuous in whole mounts, also present between bursal slits; hyalocytes and granulocytes of same size, diameter 8–10 μm (fix). Seminal vesicle absent, developing sperm in anterior half of XI. Spermatozoa c. 80 μm long, heads 20–25 μm long. Sperm funnel small, length <1 / 2 body diameter, little longer than wide (e.g. 60: 52 μm, fix), with defined outline, not deformed, collar narrower than funnel body (32 μm). Vas deferens 4–5 μm wide (viv, fix). Male copulatory organ: bursal slit longitudinal; male gland small, only slightly projecting into body cavity, not flattened, c. 40 μm long, 30 μm wide, 30 μm high (fix). Subneural glands and other accessory glands absent. Spermatheca: small ectal gland, ectal duct shorter than body diameter, c. 1.5 x as long as ampulla, c. 90 μm long, diameter c. 12 μm, proximal endpiece slightly projecting into ampulla, not widened; two broadly sessile diverticula or diverticula-like protrusions, diameter c. 18 μm, sperm-containing; ampulla tapering proximad, diverticula and ampulla apparently solid (viv) but lumina visible in whole mounts. One mature oocyte at a time, extending over 1.5–2 segment lengths. Remarks. Using the tabular comparison of Fridericia species with two spermathecal diverticula in Dózsa- Farkas (2009), F. sousai sp. nov. belongs to a group of 11 species, characterized by separate spermathecae and globular, hemispherical, or short-stalked diverticula. In this group, only F. isseli Rota, 1994 shares the following combination of characters with F. sousai: length <10 mm, less than 40 segments, max. 4 chaetae per bundle, oesophageal appendages short, unbranched, four pairs of preclitellar nephridia, chylus cells preclitellar, coelomocytes with refractile vesicles, seminal vesicle and subneural glands absent, spermatheca with ectal gland. F. isseli differs from the new species in the following traits, among others: (1) chylus cell canals branched, not widened (vs. unbranched, sac-like), (2) clitellum saddle-shaped (vs. girdle-shaped), (3) male gland tripartite with two small accessory glands (vs. accessory glands absent). In the key to Fridericia species in Schmelz (2003), F. sousai would key out together with F. isseli and with F. w a l d e n s t ro e m i Rota & Healy, 1999. The latter differs from F. s o u s a i in having 40–54 segments, five preclitellar pairs of nephridia, a small subneural gland in XIV, and proximally fused spermathecae with long-stalked diverticula, among other characters. Figure 5 and Table 2 give a comparison of F. sousai with the other three new species of Fridericia from the same site.Published as part of Schmelz, Rüdiger M. & Collado, Rut, 2013, Enchytraeidae (Oligochaeta, Annelida) from a field site in Portugal, with the description of five new species and a redescription of Enchylea heteroducta Nielsen & Christensen, 1963, pp. 307-328 in Zootaxa 3647 (2) on pages 310-311, DOI: 10.11646/zootaxa.3647.2.4, http://zenodo.org/record/21898

Enchytraeidae (Oligochaeta, Annelida) from a field site in Portugal, with the description of five new species and a redescription of Enchylea heteroducta Nielsen & Christensen, 1963

Schmelz, Rüdiger M., Collado, Rut (2013): Enchytraeidae (Oligochaeta, Annelida) from a field site in Portugal, with the description of five new species and a redescription of Enchylea heteroducta Nielsen &amp; Christensen, 1963. Zootaxa 3647 (2): 307-328, DOI: 10.11646/zootaxa.3647.2.