Indigenous communities of soil-resident nematodes have a high potential for soil health assessment as nematodes are diverse, abundant, trophically heterogeneous and easily extractable from soil. The conserved morphology of nematodes is the main operational reason for their under-exploitation as soil health indicators, and a user-friendly biosensor system should preferably be based on nonmorphological traits. More than 80% of the most environmental stress-sensitive nematode families belong to the orders Mononchida and Dorylaimida. The phylogenetic resolution offered by full-length small subunit ribosomal DNA (SSU rDNA) sequences within these two orders is highly different. Notwithstanding several discrepancies between morphology and SSU rDNA-based systematics, Mononchida families (indicated here as M1-M5) are relatively well-supported and, consequently, family-specific DNA sequences signatures could be defined. Apart from Nygolaimidae and Longidoridae, the resolution among Dorylaimida families was poor. Therefore, a part of the more variable large subunit rDNA (≈ 1000 bp from the 5'-end) was sequenced for 72 Dorylaimida species. Sequence analysis revealed a subclade division among Dorylaimida (here defined as D1-D9, PP1-PP3) that shows only distant similarity with 'classical' Dorylaimid systematics. Most subclades were trophically homogeneous, and - in most cases - specific morphological characteristics could be pinpointed that support the proposed division. To illustrate the practicability of the proposed molecular framework, we designed primers for the detection of individual subclades within the order Mononchida in a complex DNA background (viz. in terrestrial or freshwater nematode communities) and tested them in quantitative assays (real-time polymerase chain reaction). Our results constitute proof-of-principle for the concept of DNA sequence signatures-based monitoring of stress sensitive nematode families in environmental samples.

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This contribution presents a study of Iberian and Californian populations of Aporcelaimellus simplex, including morphological, morphometric and molecular data. The species is characterised and distinguished by its lip region offset by an expansion, pars refringens vaginae absent, and conical tail with a small but distinct hyaline terminal portion. No significant difference exists between American and European populations. Molecular data and the derived evolutionary tree show a topology in which this species forms a well-supported group with members of Discolaiminae, far from other representatives of Aporcelaimellus. Putting special emphasis in the absence of pars refringens vaginae, A. simplex is transferred to the genus Aporcella. The taxonomy of this genus is revised in depth, with the proposal of an emended diagnosis, the provision of a list of 13 valid species (mostly new combinations from Aporcelaimellus) as well as a key to their identification and a compendium of their main morphometrics. Aporcella debruinae sp. n. is proposed for Aporcelaimellus papillatus apud de Bruin & Heyns, 1992.

A new species of the genus Oscheius, O. saproxylicus sp. n., collected in decaying wood obtained from an orchard in Southern Iberian Peninsula, is reported. A detailed description, including morphometrics, LM and SEM images, and molecular (18S and 28S rDNA genes) information is provided. The female is characterized by a moderately long body, lateral field with three longitudinal ridges, midbody vulva, and conical tail with acute tip. It was distinguished from its closest relative, O. dolichura, by a shorter tail and longer rectum. The male was not found. Morphological and molecular data support its belonging to Dolichura-group. Molecular analyses show that both Insectivorus and Dolichura groups are related to each other, being proposed as subgenera of the genus Oscheius as Oscheius and Dolichorhabditis. Finally, an updated taxonomy of the genus is presented, with generic and subgeneric diagnoses, list of species and a key to their identification.

Two very similar species of the genus Chiloplacus, namely C. magnus and C. insularis, are re-described and compared based on type material as well as Iberian specimens. Relevant new information is obtained for their characterisation and for elucidating their identity with more accuracy. Special mention is deserved by the findings regarding: i) the morphology of the lateral field at vulval level; and ii) the location of the vulva, which is either midventral or subventral, two remarkable traits that were originally overlooked. Chiloplacus magnus is distinguished by having the left lateral field expanded at vulval level and the vulva displaced to a subventral position, whereas C. insularis displays the usual pattern of the genus. The evolutionary relationships of the Iberian C. magnus are explored by means of D2-D3 sequence analysis. Chiloplacus similis is regarded as identical to C. magnus and is proposed as a new junior synonym of the latter.

The morphology of dorylaimid spicules is richer than usually conceived and shows interesting interspecific variations that have not received much attention. New ideas are proposed to describe these structures, including a delimitation or definition of their parts and a series of morphometries, either (absolute) measurements or ratios. Three descriptive examples are presented. Several morphological characters (head shape, development of the ventral hump, etc.) and a number of morphometric features (total and relative lengths, relative size of the median piece, terminal tip width, etc.) are especially useful for species characterisation and comparative purposes.

Aporcella charidemiensis sp. n. is described from the southern Iberian Peninsula. It is characterised by its 1.38-1.81 mm long body, lip region offset by constriction and 16-17 μm broad, odontostyle 12-13 μm long with aperture occupying 65-73% of its length, 354-420 μm long neck, pharyngeal expansion 164-212 μm long or 46-51% of total neck length, uterus a simple tube-like structure 79-155 μm long or 1.7-3.0 times the corresponding body diam., pars refringens vaginae absent, transverse vulva (V = 53-62), convex conoid tail (24-35 μm, c = 46-69, c = 0.8-1.1), 59-63 μm long spicules, and 7-10 irregularly spaced ventromedian supplements bearing a hiatus. The analyses of LSU-DNA sequences of the new species confirm the previous results regarding the phylogeny of the genus Aporcella.

The first available compilation of Iberian soil and freshwater nematodes is presented in this paper. The inventory is currently made up of 981 species belonging to 236 genera, 77 families and 12 orders. Data of the Iberian nematode fauna are compared with other components of the Iberian biota, as well as the nematode fauna of other geographical regions. Quantitative and qualitative aspects of the nematode inventory are analyzed and discussed, paying special attention to the kind of information available for each species, and concluding that practically one-third of Iberian species are deficiently characterized and need further study. Endemicity of Iberian species is also considered: 143 species, 14.6% of the total, are restricted (in their distribution) to the Iberian geography, most of them being members of the orders Dorylaimida (87) and Tylenchida (29), which are also the most diversified nematode taxa. Practical or applied interest of knowledge of the Iberian nematode fauna is commented and supported with examples and recent contributions. Finally, an alphabetical list of the species, ordered by specific name, is provided. Key words: Balearic Islands, Compilation, Endemisms, Faunistics, Freshwater, Iberian Peninsula, Nematoda, Soil. RESUMEN Nematodos edáficos y de agua dulce de la fauna ibérica: una síntesisEn esta contribución se presenta una recopilación de las especies ibéricas de nematodos de suelo y de agua dulce, la primera de este tipo realizada hasta el momento. El inventario actual lo componen 981 especies de 236 géneros, 77 familias y 12 órdenes. Los datos correspondiente a la fauna ibé-rica de nematodos se compara con la de otros táxones de la biota ibérica. Se analizan y se discuten distintos aspectos cuantitativos y cualitativos de la fauna nematológica, con especial énfasis en el tipo de información disponible sobre cada especie, y se concluye que casi una tercera parte de las especies ibéricas permanecen insuficientemente caracterizadas, razón por la cual requieren de estudios adicionales. La endemicidad de las especies es así mismo objeto de atención: 143 especies, un 14.6% del total están restringidas en su distribución al ámbito ibérico, en su mayor parte pertenecientes a los órdenes Dorylaimida (87) y Tylenchida (29), por otra parte los más diversificados de entre los pertenecientes al filo. El interés básico y aplicado del conocimiento de la fauna de nematodos es comentado e ilustrado con aportaciones recientes y ejemplos. Por último, se presenta una lista de todas las especies de la fauna ibérica, ordenadas alfabéticamente por su epíteto específico. Palabras clave: Agua dulce, Compendio, Endemismos, Faunística, Islas Baleares, Nematodos edáficos, Península Ibérica, Suelo. SOIL AND FRESHWATER NEMATODES OF THE IBERIAN FAUNA: A SYNTHESIS180 PEÑA-SANTIAGO, ABOLAFIA, GUERRERO, LIÉBANAS & PERALTA IntroductionThe biodiversity of any territory is one of its main distinctive features and its characterization serves fundamental and applied purposes. The biota of soil and freshwater sedimen...