Biodiversity response to climate change in a warm deep sea

Climate changes are expected to induce significant modifications in biodiversity on the global scale, but little is known as to how biodiversity has been affected by recent changes in the deep sea. We have used nematodes to investigate the response of deep‐sea biodiversity to an extensive climate anomaly that modified the physico‐chemical characteristics of the deep waters of the Eastern Mediterranean. Using a decadal data set (from 1989 to 1998), we provide evidence that deep‐sea nematode diversity can be strongly and rapidly affected by temperature shifts. The abrupt decrease in temperature (of about 0.4 °C) and modified physico‐chemical conditions that occurred between 1992 and 1994 caused a significant decrease in nematode abundance and a significant increase in diversity. This temperature decrease also resulted in decreased functional diversity and species evenness, and in an increase in the similarity to colder deep‐Atlantic fauna. When the temperature recovered (after 1994–1995), the biodiversity only partially returned to previous values. We conclude that deep‐sea fauna is highly vulnerable to environmental alteration, and that deep‐sea biodiversity is also significantly affected by very small temperature changes. The results presented here provide new elements towards a better understanding of the potential large‐scale consequences of climate change.     

A preliminary investigation into the potential use of a hydrocyclone to concentrate entomopathogenic nematodes from suspension

A 32-mm diameter hydrocyclone was used to investigate whether the entomopathogenic nematode Steinernema carpocapsae could be recovered and concentrated from a dilute suspension. By altering the sizes of the underflow and overflow apertures of the hydrocyclone, it was possible to recover high percentages of the nematodes from the initial suspension in reduced volumes of fluids. All underflow and overflow configurations tested gave an increased concentration of nematodes in the underflow of between 1.26 and 4.55 times the initial feed concentration. The highest nematode concentrations were achieved with a 4-mm underflow and an 8-mm overflow. It is proposed that through further refinements of hydrocyclone performance, it may be possible to utilise hydrocyclones in the recovery and harvesting processes of in vitro nematode production systems.     

The Society of Nematologists at 50, and Where to from Here?

Nathan Cobb, as the father figure of the Society of Nematologists, set an example to later generations of nematologists in his studies of nematode biology. In the 50 years of the Society’s existence nematological research has greatly expanded that knowledge base. Opportunities over the next 50 years are boundless in view of advancing technologies and emerging challenges, and this leads to speculation as to what future nematological research advances will enhance peoples’ quality of life.     

Dorylaimellus egmonti n. sp. (Nematoda: Dorylaimida) from Taranaki,New Zealand

Abstract

Dorylaimellus egmonti n. sp. from New Zealand can be distinguished from D. montenegricus Andrássy, 1959, and from D. monticolus Clark, 1963, by the presence of prominent globular structures in the anterior part of the oesophageal bulb. It is further distinguished from D. montenegricus by the relatively longer basal oesophageal bulb, and from D. monticolus by the differently shaped tail.     

Resistance of nonlambing exotic and domestic ewes to naturally acquired gastrointestinal nematodes

No breed differences in Haemonchus contortus burdens were found when nonlacfating exotic (St. Croix and Barbados Blackbelly), domestic (Finn-Dorset × Rambouillet) and $\text{1}\text{2}\text{exotic}\text{-}\text{1}\text{2}$ domestic ewes grazed fall pasture, but all ewes had significantly (p < 0.05) lower worm burdens at necropsy than tracer lambs grazing the same pasture. Florida Native ewes grazing the same pasture showed significantly (p < 0.05) less packed cell volume (PCV) decrease and significantly (p < 0.05) lower fecal egg counts than the other ewe breeds but were not available for necropsy. Tracer lambs had a significantly (p < 0.05) greater PCV decrease and significantly (p < 0.05) higher fecal egg counts than ewes.The results of this study suggest that breed differences in the periparturient rise in fecal egg counts of exotic and domestic ewes observed in an earlier study may have been caused by breed differences in the periparturient relaxation of immunity rather than breed differences in the ability to acquire immunity to worms.     

Estuarine nematodes as indicators of organic pollution; An example from the Ems estuary (The Netherlands)

A comparison is made of the structure and abundance of the nematode community of an intertidal, brackish-water mudflat in the Ems estuary under conditions of high (1980) and reduced (1987) organic waste input. Three stations, at different distances from the waste water inlet, were sampled monthly; nematodes were identified and counted in the upper 1 cm of the sediment. In 1987, numerical density of nematodes was lower, and species diversity was higher than in 1980. Diatom eating nematode species dominated in 1980, to decrease by 1987.Eudiplogaster pararmatus, an indicator of organic enrichment, also decreased strongly. The response of the nematode community to reduced organic waste input could be adequately described with the BONGERS' Maturity Index.     

Physiological and morphological studies on secretion of a protein-carbohydrate complex by a nematode

Dropkin V. H. and Bird Alan F. 1978. Physiological and morphological studies on secretion of a protein-carbohydrate complex by a nematode. International Journal for Parcsitology8: 225–232. Secretion of the gelatinous matrix by females of Meloidogyne javanica was induced by compounds extracted from the roots of either susceptible or resistant plants. The stimulus that induced this secretion was not specific but analysis of root extracts implicated the nucleic acids. DNA was the most active substance tested (minimum concentration = 0·0075 mg/ml). The response was rapid, usually within 10 min and did not appear to be nerve mediated. The shape of the exudate in vitro was conditioned by the composition of the medium in which the nematodes were tested.Stimulation brought about significant changes in the nuclei of the rectal gland cells which enlarged, in the nucleoli, which tended to become more granular and vacuolated, and in the cytoplasm, where there was an increase in the number of Golgi bodies per unit area.     

Interactions among nitrogen-transforming bacteria and nitrogen-fixingPisum sativum L. in laboratory sand columns

Plants of barley (Hordeum vulgare), ryegrass (Lolium perenne), pea (Pisum sativum) or turnip (Brassica campestris rapifera) were grown in pots of unfertilised soil for 10 weeks together with unplanted control pots. A wide range of soil microbiological parameters was measured on bulk soil samples 2, 4, 7 and 10 weeks after seedlings were transplanted. There was no effect of planting or differential effect of plant species upon respiration rate, microbial biomass N, or biomass of microbial predators, but these parameters all varied significantly over time. Respiration, biomass N and nematode biomass all increased, whilst protozoan biomass decreased. Microbial biomass C showed no significant temporal changes or effect of planting. There was evidence for differential plant effects on potential nitrification and denitrification. Nitrification rates were depressed, compared with the fallow, in all treatments except the pea, at some time in the experiment. Conversely denitrification rates were enhanced in all treatments, except the grass, at specific times. Denitrification rates were greater in the pea treatment than the fallow on all occasions. These results demonstrate that plants do not necessarily influence the gross microbiology of the soil, but may affect physiologically distinct sub-components of the microbial biomass.     

Morphology,phylogeny and taxonomy of the genus Sectonema (Nematoda,Aporcelaimidae)

This contribution provides new insights in the phylogeny and taxonomy of the nematode genus Sectonema with an integrative approach. A brief historical outline of the matter is presented. Then, the morphological pattern of the genus is revised and illustrated, the nature of its stomatal protruding structure, either a reduced odontostyle or a mural tooth, being its most relevant diagnostic feature. The existence of cilia‐ or seta‐like structures in the perioral area and/or at the anterior part of cheilostom of some species is evidenced by SEM observations for the first time. Available molecular data (D2–D3 LSU‐rRNA gene) are analysed, including two new sequences of S. septentrionale from Spain. The monophyly of the genus is confirmed, and two species groups with geographical projection are tentatively identified. A close relationship with Metaporcelaimus is also demonstrated as both taxa constitute a highly supported clade. A likely polyphyly of the family Aporcelaimidae is once more demonstrated. Finally, an updated taxonomy of the genus is proposed, including revised diagnosis, list of species, identification key and a compendium of their main morphometrics.     

Physicochemical and biological properties of the coffee (Coffea arabica) rhizosphere suppress the root-knot nematode Meloidogyne exigua

ABSTRACT

We investigated the properties of rhizospheric soils infested with root-knot nematode (RKN) Meloidogyne exigua in 17 coffee (Coffea arabica) farms from the Southern region of Minas Gerais, Brazil. Physicochemical (pH, clay and organic matter) and biological properties (RKN parasites and microbiota volatile toxicity on M. exigua) were correlated with the number of second-stage juveniles (J₂) and the egg hatching of M. exigua extracted from those rhizospheres. In the five most suppressive farms, the number of J₂ was less than 50/100?g of soil and the egg hatching was significantly low. The bacterium Pasteuria penetrans was found in four of the most suppressive farms with an average of 30% of J₂ infected with endospores. By using in vitro experiments the microbiota volatiles emitted from the most suppressive soils killed more than 83% of the J₂. Additionally, volatiles produced by Fusarium oxysporum, Cladosporium sp. and Syncephalastrum sp. isolated from M. exigua eggs, significantly killed the J₂. Identification of nematicidal compounds from the soils by GC-MS supported the strong involvement of the microbiota volatile toward RKN suppressiveness. Clay percentage and pH were similar in farms with the most suppressive soils (42.5% and 6.6%, respectively). Finally, the most suppressive soils came from farms with the highest coffee bean yields. Collectively, these results suggest the strong involvement of parasitic microorganisms, clay percentage and the pH suppressing RKN in soils from the major coffee production region in Brazil, and that volatiles emitted from total microbiota and exclusively from egg-isolated fungi are toxic to M. exigua.