Morphological differences between free-living soil and freshwater nematodes in relation to their environments

There is no single feature to distinguish free-living soil nematodes from freshwater nematodes, also because all free-living nematodes are essentially aquatic. This notwithstanding, by examining the frequencies of some characters of 1141 European species, differences of qualitative/quantitative characters between soil and freshwater nematodes were found. In particular, aquatic and semi-aquatic species are, on average, longer and slimmer than soil species, have a longer tail, greater body weight, smooth cuticle and larger amphids. A new body parameter, length of the pharynx in relation to the length of the whole digestive tract (e), was also taken into consideration.

Is a biogeography of freshwater nematodes possible?

An attempt was made to detect some possible biogeographic patterns in the distribution of freshwater nematodes. The literature concerning 14 geographic areas (in Eurasia, Africa and America) and seven well studied lakes was examined. Notwithstanding the ubiquity of most freshwater nematodes, some distributional patterns emerge from a multidimensional analysis. Examining the lakes only, nematodes in Lake Baikal appear markedly different from the other lacustrine nematodes from other parts of the world. It is possible to conclude: i) that freshwater nematodes communities show some difference at the continental level only; and ii) that the freshwater nematode biota is divided into two parts with the Lake Baikal community as one part, and the rest of the world community as the other.

Moss inhabiting nematodes: influence of the moss substratum and geographical distribution in Europe

Abstract

The impact of the moss substratum (soil or rock) on the species composition of nematode assemblages was investigated. Samples of different species of moss were collected at several stations in Italy. Nematode density was very variable between samples and substrata, but nematode assemblages were very similar in trophic group structure and diversity. Predator dominance and the high percentage of Dorylaimida indicate the good quality of the investigated stations. Species richness and biomass were higher in mosses growing on soil where large nematodes such as Aporcelaimellus obtusicaudatus were abundant. No clear substratum-dependent species pattern was found: only Tripylella intermedia appears to be exclusive for mosses growing on rocks. Prionchulus muscorum and Plectus acuminatus were the commonest species and occurred in almost all samples. By comparing our moss communities with those of other European communities reported in the literature, we detected significant differences between continental and Mediterranean communities.

Read-out of soft X-ray contact microscopy microradiographs by focused ion beam/scanning electron microscope

A novel focused ion beam-based technique is presented for the read-out of microradiographs of Caenorhabditis elegans nematodes generated by soft x-ray contact microscopy (SXCM). In previous studies, the read-out was performed by atomic force microscopy (AFM), but in our work SXCM microradiographs were imaged by scanning ion microscopy (SIM) in a focused ion beam/scanning electron microscope (FIB/SEM). It allows an ad libitum selection of a sample region for gross morphologic to nanometric investigations, with a sequence of imaging and cutting. The FIB/SEM is less sensitive to height variation of the relief, and sectioning makes it possible to analyse the sample further. The SXCM can be coupled to SIM in a more efficient and faster way than to AFM. Scanning ion microscopy is the method of choice for the read-out of microradiographs of small multicellular organisms.

The nematode community of two Italian rivers (Taro and Ticino)

Abstract

The Taro and Ticino rivers were sampled (maximum 15 cm depth) for nematodes during 1 year at three sites for each river and some ecological parameters were measured. The yearly mean abundance of nematodes in the river Taro was 23 individuals/10 cm2 and in the river Ticino 79 individuals/10 cm2. In the two rivers five to 15 and three to ten species, respectively, were found. The highest station (Taro 1) of the river Taro was significantly different from all the other Taro and Ticino stations both for number and species composition: bacterial feeders were the dominant group in Taro 1 (mean Maturity Index (MI) was 2.25), whereas unicellular eukaryote feeders dominated the other Taro and Ticino sites (mean MI of 2.85). Chromadorina bioculata was the most common species in both rivers, except at Taro 1, where Eumonhystera dispar dominated. Significant correlations were found between conductivity and unicellular eukaryote feeders and bacterial feeders. For the first time the Distinctness Index δ+ is used for freshwater nematodes. Comparing our communities with other Italian rivers (data taken from the literature), we detected significant differences between polluted and not polluted habitats.

Fourier transform infrared microspectroscopy as a new tool for nematode studies

We report the results of a microspectroscopy study on the Fourier transform infrared (FT-IR) absorption spectra of Caenorhabditis elegans, collected from the different parts of a single intact specimen--pharynx, intestine and tail regions. The principal absorption bands were assigned to the molecular species present in C. elegans, with an excellent reproducibility for the pharynx spectrum. These results enabled us to explore if FT-IR microspectroscopy could offer a new tool for nematode identification. As an example, the discrimination among four well characterised nematode taxa is reported. The FT-IR results completely match those obtained by Blaxter and colleagues through molecular biology [Nature 392 (1998) 71].

New records of alien monogeneans from Lepomis gibbosus and Silurus glanis in Italy

The first geographical records of five alien monogeneans for Italy is reported. Four species have been detected from Lepomis gibbosus (Linnaeus, 1758): Actinocleidus recurvatus Mizelle et Donahue, 1944, Actinocleidus oculatus (Mueller, 1934), Urocleidus similis (Mueller, 1936) and Urocleidus dispar (Mueller, 1936); one species from Silurus glanis Linnaeus, 1758: Thaparocleidus vistulensis (Siwak, 1932) n. comb.

Free-living nematodes from nature reserves in Costa Rica. 2. Mononchina

Abstract

In soil, moss and freshwater habitats of tropical forests in Costa Rica, 20 mononch species were found. Two are described as new species. Mononchus laminatus n. sp. (L = 1.5-1.9 mm, buccal capsule 29-31 × 11-14 μm, c′ = 3.6-4.9, similar to M. aquaticus but with a subventral lamina present in anterior part of buccal cavity, and amphid aperture posterior to the dorsal tooth) and Miconchus gomezi n. sp. (similar to M. digiturus, but with slender body, vulva cuticularised and with a reduced posterior genital branch). The known species are redescribed, the well-known ones briefly, the less known more extensively. Brazilian and Costa Rican specimens of Paracrassibucca paucidentata Lordello, 1970 were studied and a lectotype has been designated. The other species found are: Mononchus truncatus Bastian, 1865; M. aquaticus Coetzee, 1968; M. tunbridgensis Bastian, 1865; Coomansus parvus (de Man, 1880); Coomansus sp. (C. zschokkei-group); Prionchulus muscorum (Dujardin, 1845); P.punctatus Cobb, 1917; Cobbonchus coetzeeae Andrássy, 1970; Mylonchulus contractus Jairajpuri, 1970; M. hawaiiensis (Cassidy, 1931); M. obtusicaudatus (von Daday, 1899); M. parabrachyuris (Thorne, 1924); M. sigmaturus Cobb, 1917; Mulveyellus monhystera (Cobb, 1917); Iotonchus tenuidentatus (Kreis, 1924); I. trichurus Cobb, 1917 and Miconchus digiturus (Cobb, 1893).

Free-living nematodes from nature reserves in Costa Rica. 3. Araeolaimida

Abstract

Seven species of Araeolaimida were found in soil, moss and freshwater habitats of tropical forests in Costa Rica. Three are described as new. Anonchus pulcher n. sp. is characterised by slender body, lip region demarcated by a depression, presence of ca 45- 60 sublateral glands on each side of the body and monoprodelphic female genital apparatus. Paraplectonema americanum n. sp. lacks somatic setae, the stoma is 3.0-3.4 lip region diameter long, the female rectum measures 26 μm, the male tail 137-153 μm, presence of ten to 11 male supplements, spicula 28-30 μm long, gubernaculum of complicated shape with a caudal apophysis. Chronogaster costaricae n. sp. is characterised by absence of longitudinal incisures, rows of spines, crystalloids and vacuolated glandular bodies, terminus with open mucro with one or two basal spines. The species redescribed, either briefly for well known, or more extensively for less well known, species are: Plectus patagonicus de Man, 1904; P.indicus Khera, 1972; Chronogaster serrulata Loof, 1973 and C. cameroonensis Heyns & Coomans, 1984.

Morphology and systematics of the genus Anonchus Cobb, 1913 (Nematoda: Leptolaimina) and reappraisal of the family Aphanolaimidae Chitwood, 1936 n. rank

Abstract

The genus Anonchus is revised. The genera Assia and Haconnus are considered to be synonymous with Anonchus on the basis of the morphological analysis. Additional descriptions of six species, viz. A. maculatus , A. mirabilis , A. millelacunatus , A. palaeotropicus , A. coomansi and A. pulcher are provided on the basis of type material or recently collected populations. The lectotype of A. monohystera is designated and described and the synonymy of this species with A. maculatus is confirmed. Two new species are described; A. winiszewskae sp. n. from Paraguay and A. venezolanus sp. n. from Venezuela. Several aspects of the morphology are described and the variability and diagnostic significance of the main morphological characters discussed. A study of intrageneric and suprageneric taxonomy of the genus Anonchus is presented. The subfamily Aphanolaiminae is reinstated for the genera Aphanolaimus, Aphanonchus and Paraphanolaimus and raised to family rank. The family Aphanolaimidae includes two subfamilies: Aphanolaiminae and Anonchinae. An emended diagnosis and a revised classification of Anonchus are proposed and a key to the species of the genus is provided.

Freeliving nematodes from nature reserves in Costa Rica. 1. Dorylaimina

Abstract

This article gives the first results of a study of dorylaims found in nature reserves in Costa Rica. The material examined shows the great interest of the nematofauna of these reserves. Two species were found for which new generic names had to be erected: Parapalus n.gen. for a species resembling Paraxonchium but with a long symmetrical odontostyle as in Gopalus; the single species P.arboricola n.sp. lives in epiphytic mosses. Inbionema n.gen. is conspicuous for the very widely separate lips and the long (but not needle-shaped) odontostyle; the single species I. biforme n.sp. (named because there are two classes of odontostyle length, under 44 and over 59 μ m) lives in the same habitat as the previous species. Other new species found are: Pachydorylaimus schizodontus n.sp. (furcate part ca 33% of odontostyle length), Sicorinema esquiveli n.sp. (cuticular annules 0.5 μ m wide, body length over 1 mm); Brasilaimus bidentatus n.sp. (24-26 longitudinal ridges, each onchium with an additional denticle), B. vinciguerrae n.sp. (32 ridges, odontostyle slender), Xiphinemella monohystera n.sp. (female monodelphic, tail conoid in both sexes) and Tyleptus bongersi n.sp. (liplets amalgamated into disc-like structure, distance vulva-cardia very short). The female of Idiodorylaimus annulatus (von Daday, 1905) is reported for the first time. The following nominal species were found and redescribed: Practinocephalus secundus Andrássy, 1986, Axonchium labiatum Thorne, 1939, Metaxonchium micans (Thorne, 1939), Oxydirus tropicus Thorne, 1964, O. tenuicaudatus Thorne, 1964, Funaria acuta (Zullini, 1973), Caveonchus saccatus (Goseco et al., 1981) and Sclerostylus xiphinemoides (Monteiro, 1970). A key to the species of Pachydorylaimus is given. The subfamily Paraxonchiinae and the position of the genus Gopalus are discussed. Nématodes libres des réserves naturelles du Costa Rica. 1. Dorylaimina - Cet article donne les premiers résultats d'une étude sur les Dorylaimides récoltés dans les réserves naturelles du Costa Rica. Le matériel examiné montre le grand intérêt de la nématofaune de ces réserves. Il a été trouvé deux espèces pour chacune desquelles un nouveau genre a dß être créé: Parapalus n.gen. pour une espèce ressemblant à Paraxonchium mais possédant un odontostyle long et symétrique comme chez Gopalus; l'espèce unique P. arboricola n.sp. vit dans les mousses épiphytes. Inbionema n.gen. se distingue par ses lèvres largement séparées et un odontostyle long mais non aciculaire; l'espèce unique I. biforme n.sp. - ainsi nommé à cause des deux classes de longueur de son odontostyle, moins de 44 et plus de 59 μ m - occupe le même habitat que la précédente espèce. Les autres nouvelles espèces rencontrées sont: Pachydorylaimus schizodontus n.sp. (partie fourchue de l'odontostyle équivalent à 33% de sa longueur totale), Brasilaimus bidentatus n.sp. (24-26 crêtes longitudinales; chaque onchium pourvu d'une denticule additionnelle), B. vinciguerrae n.sp. (32 crêtes longitudinales; odontostyle mince), Sicorinema esquiveli n.sp. (longueur du corps de plus d'1 mm; largeur des anneaux cuticulaires 0.5 μ m), Xiphinemella monohystera n.sp. (femelle monoprodelphe; queue conoïde chez les deux sexes) et Tyleptus bongersi n.sp. (petites lèvres amalgamées en une structure discoïde; distance cardia - vulve très courte). La femelle d'Idiodorylaimus annulatus est signalée pour la première fois. Les espèces nominales suivantes ont été récoltées et sont redécrites: Practinocephalus secundus Andrássy, 1986, Axonchium labiatum Thorne, 1939, Metaxonchium micans (Thorne, 1939), Oxydirus tropicus Thorne, 1964, O. tenuicaudatus Thorne, 1964, Funaria acuta (Zullini, 1973), Caveonchus saccatus (Goseco et al. , 1981) and Sclerostylus xiphinemoides (Monteiro, 1970). Une clé des espèces du genre Pachydorylaimus est proposée. La sous-famille des Paraxonchiinae et la position du genre Gopalus sont discutées.

Observations on the Bionomics of the Freshwater Nematode Chromadorina bioculata

The biology and morphology of Chromadorina bioculata is presented. Tile nematode was abundant on the alga Cladophora of one lily pond, but absent from similar habitats in nearby ponds. The setae, caudal glands, high Iocomotory rates and positive photo response have been interpreted in relation to maintenance on, amongst and between algal filaments, suspended over large volumes of water.When placed in tap or distilled water, C. bioculata became inactive and died. The influence of pH buffers, tonicity, temperature and starvation on activity were investigated. C. bioculata survived longer in artificial sea water diluted 10 or 100 times with distilled water, or in NaCl isotonic with sea water diluted 100 or 1000 times, than in tap or distilled water. No evidence of wide osmotic toleration or osmoregulation was observed. Activity was influenced by temperature, with peak activities occurring at the seasonal normal temperature. These findings are discussed in terms of general hematology and habitat selection.